This
technical report is a multimedia web page, available at
http://www.cs.dartmouth.edu/reports/TR2008-631/ .
}
}
@TechReport{Dartmouth:TR2008-630,
author = {Bruce R. Donald and Christopher G. Levey and Igor Paprotny },
title = {{Planar Microassembly by Parallel Actuation of MEMS Microrobots (Microassembly Video)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-630},
year = {2008},
month = {January},
abstract = {
Movie of a representative microassembly experiment using devices from species 1,3,4
and 5, recorded through an optical microscope. The robots are initially arranged
along the corners of a rectangle with sides 1 by 0.9 mm. The assembly experiment
is divided into three stages. During stage 1, devices 4 and 5 dock together to form
the initial stable shape. In stage 2, device 3 docks with the initial stable shape,
while during stage 3, device 1 docks with the stable shape, forming the final assembly.
}
comment = {
This technical report is a multimedia web page, available at
http://www.cs.dartmouth.edu/reports/TR2008-630/ .
}
}
@TechReport{Dartmouth:TR2008-629,
author = {Micah K. Johnson },
title = {{Lighting and Optical Tools for Image Forensics}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-629},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/476/TR2008-629.pdf},
abstract = {
We present new forensic tools that are capable of detecting traces of tampering in
digital images without the use of watermarks or specialized hardware. These tools
operate under the assumption that images contain natural properties from a variety
of sources, including the world, the lens, and the sensor. These properties may
be disturbed by digital tampering and by measuring them we can expose the forgery.
In this context, we present the following forensic tools: (1) illuminant direction,
(2) specularity, (3) lighting environment, and (4) chromatic aberration. The common
theme of these tools is that they exploit lighting or optical properties of images.
Although each tool is not applicable to every image, they add to a growing set of
image forensic tools that together will complicate the process of making a convincing
forgery.
}
comment = {
Ph.D Dissertation. Advisor: Hany Farid.
}
}
@TechReport{Dartmouth:TR2008-628,
author = {Manya K. Sleeper },
title = {{Key Management for Secure Power SCADA}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-628},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/475/TR2008-628.pdf},
abstract = {
This thesis proposes a key management protocol for secure power SCADA systems that
seeks to take advantage of the full security capacity of a given network by allowing
devices to use public key cryptography for key management if they are capable of
doing so and reverting to symmetric key cryptography only when such use is necessitated
by the weakness of a given device. Allowing devices to obtain different levels of
security permits SCADA networks to maximize their security in the decades before
such networks are capable of implementing fully public key-based key management
protocols. Such a system is obtained through the use of a protocol based on a modified
version of SSL using X.509 certificates containing encrypted symmetric keys that
allow master devices the option of using the symmetric keys for encrypting the shared
secret used to create keying material, instead of using a slave device's public
key. This thesis presents the protocol and uses proof-of-concept code to carry out
a performance evaluation of the key management scheme.
}
comment = {
Senior Honors Thesis. Advisor: Sean Smith.
}
}
@TechReport{Dartmouth:TR2008-627,
author = {Ashwin Ramaswamy },
title = {{Detecting kernel rootkits}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-627},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/474/TR2008-627.pdf},
abstract = {
Kernel rootkits are a special category of malware that are deployed directly in the
kernel and hence have unmitigated reign over the functionalities of the kernel itself.
We seek to detect such rootkits that are deployed in the real world by first observing
how the majority of kernel rootkits operate. To this end, comparable to how rootkits
function in the real world, we write our own kernel rootkit that manipulates the
network driver, thus giving us control over all packets sent into the network. We
then implement a mechanism to thwart the attacks of such rootkits by noticing that
a large number of the rootkits deployed today rely heavily on the redirection of
function pointers within the kernel. By overwriting the desired function pointer
to its own function, a rootkit can perform a proverbial man-in-the-middle attack.
Our goal is not just the detection of kernel rootkits, but also to levy as little
an impact on system performance as possible. Hence our technique is to leverage
existing kernel functionalities (in the case of Linux) such as kprobes to identify
potential attack scenarios from within the sytem rather than from outside it (such
as a VMM). We hope to introduce real-world security in devices where performance
and resource constraints are tantamount to security considerations.
}
comment = {
M.S. Thesis Proposal. Advisor: Sean W. Smith
}
}
@TechReport{Dartmouth:TR2008-626,
author = {Yurong Xu },
title = {{Anchor-Free Localization in Mixed Wireless Sensor Network Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-626},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/473/TR2008-626.pdf},
abstract = {
Recent technological advances have fostered the emergence of Wireless Sensor Networks
(WSNs), which consist of tiny, wireless, battery-powered nodes that are expected
to revolutionize the ways in which we understand and construct complex physical
systems. A fundamental property needed to use and maintain these WSNs is ``localization'',
which allows the establishment of spatial relationships among nodes over time. This
dissertation presents a series of Geographic Distributed Localization (GDL) algorithms
for mixed WSNs, in which both static and mobile nodes can coexist. The GDL algorithms
provide a series of useful methods for localization in mixed WSNs. First, GDL provides
an approximation called ``hop-coordinates'', which improves the accuracy of both
hop-counting and connectivity-based measurement techniques. Second, GDL utilizes
a distributed algorithm to compute the locations of all nodes in static networks
with the help of the hop-coordinates approximation. Third, GDL integrates a sensor
component into this localization paradigm for possible mobility and as a result
allows for a more complex deployment of WSNs as well as lower costs. In addition,
the development of GDL
incorporated the possibility of manipulated communications, such as wormhole attacks.
Simulations show that such a localization system can provide fundamental support
for security by detecting and localizing wormhole attacks. Although several localization
techniques have been proposed in the past few years, none currently satisfies our
requirements to provide an accurate, efficient and reliable localization for mixed
WSNs. The contributions of this dissertation are: (1) our measurement technique
achieves better accuracy both in measurement and localization than other methods;
(2) our method significantly improves the efficiency of localization in updating
location in mixed WSNs by incorporating sensors into the method; (3) our method
can detect and locate the communication that has been manipulated by a wormhole
in a network without relying on a central server.
}
comment = {
Ph.D Dissertation. Advisor: Fillia Makedon.
}
}
@TechReport{Dartmouth:TR2008-624,
author = {Ruslan Y. Dimov },
title = {{Making RBAC Work in Dynamic, Fast-Changing Corporate Environments}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-624},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/472/TR2008-624.pdf},
abstract = {
In large organizations with tens of thousands of employees, managing individual people's
permissions is tedious and error prone, and thus a possible source of security risks.
Role-Based Access Control addresses this problem by grouping users into roles, which
reflect job functions in the corporation. Permissions are assigned to roles instead
of directly to users, which means that all users assigned to a role have the same
set of permissions with respect to that role. However, adoption of RBAC in organizations
such as investment banks is hindered by two main factors: first, it is costly and
time-consuming to define roles. Second, there are certain job functions (such as
consultant) that cannot be expressed as RBAC roles, because their users need to
have different permission sets. The topic of this thesis is to investigate whether
roles can be applied to domains that exhibit the peculiarities of the investment
bank example. We introduce a new framework for roles that allows us to separately
represent what the role means as a job function, and what permissions its individual
users have. That way we maintain the key property of RBAC - that the number of roles
is small, while allowing for variations among users. We have also investigated machine
learning approaches in order to figure out whether roles are concepts that can be
learned or approximated by a function. We present our findings that certain learning
schemes, such as Probably Approximately Correct (PAC) earning and Instance-based
learning are not applicable to roles, while others - such as decision-tree learning,
might be useful.
}
comment = {
Senior Honors Thesis. Advisor: Sean Smith.
}
}
@TechReport{Dartmouth:TR2008-623,
author = {Jeffrey Fielding },
title = {{Linkability in Activity Inference Data Sets}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-623},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/471/TR2008-623.pdf},
abstract = {
Activity inference is an active area of ubiquitous computing research. By training
machine learning algorithms on data from sensors worn by volunteers, researchers
hope to develop software that can interact more naturally with the user by inferring
what the user is doing. In this thesis, we use the same sensor data to infer which
volunteer is carrying the sensors. Such inference could be useful -- for example,
a mobile device might infer who is carrying it and adapt to that user's preferences.
It also raises some privacy concerns, since an attacker could learn more about a
user by linking together several sensor traces from the same user. We develop a
model to differentiate users based on their sensor data, and examine its accuracy
as well as the potential benefits and pitfalls.
}
comment = {
Senior Honors Thesis. Advisors: Tanzeem Choudhury and David Kotz.
}
}
@TechReport{Dartmouth:TR2008-621,
author = {Ming Li },
title = {{Group-Aware Stream Filtering}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-621},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/470/TR2008-621.pdf},
abstract = {
Recent years have witnessed a new class of monitoring applications that need to continuously
collect information from remote data sources. Those data sources, such as web click-streams,
stock quotes, and sensor data, are often characterized as fast-rate high-volume
``streams''. Distributed stream-processing systems are thus designed to efficiently
use system resources to serve the data-acquisition needs of the applications. Most
of the state-of-the-art stream-processing systems assume an Ethernet-based network
whose bandwidth is abundant, and focus on mechanisms to save computational power
and memory. For applications involving wireless networks, particularly multi-hop
mesh networks, we recognize that the most limiting factor in efficiently processing
streams lies in the network's highly constrained bandwidth. Hence, this dissertation
proposes a group-aware stream filtering approach that saves bandwidth at the cost
of increased CPU time, for low-bandwidth data-streaming systems.
This approach, used together with multicasting, exploits two overlooked properties
of monitoring applications: 1) many of them can tolerate some degree of ``slack''
in their data quality requirements, and 2) there may exist multiple subsets of the
source data satisfying the quality needs of an application. We can thus choose the
``best alternative'' subset for each application to maximize the data overlap within
the group to best benefit from multicasting. After proving the problem NP-hard,
we introduce a suite of heuristics-based algorithms that ensure data quality, specifically
data granularity and timeliness, in addition to preserving network bandwidth.
Our framework for group-aware stream filtering is extensible and supports a diverse
range of filtering needs of monitoring applications. We evaluate this approach with
a prototype system based on real-world data sets. The results show that quality-managed
group-aware filtering is effective in trading CPU time for bandwidth savings, compared
with self-interested stream filtering. We also evaluate the effect of each algorithm
on temporal freshness of the data. Finally, we discuss other application realms
that might benefit from group-aware stream filtering.
}
comment = {
Ph.D Dissertation. Advisor: David Kotz Thesis committee: David Kotz, Andrew Campbell,
Paul Thompson, Apratim Purakayastha
}
}
@TechReport{Dartmouth:TR2008-620,
author = {Udayan Deshpande },
title = {{A Dynamically Refocusable Sampling Infrastructure for 802.11 Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-620},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/469/TR2008-620.pdf},
abstract = {
The edge of the Internet is increasingly wireless. Enterprises large and small, homeowners,
and even whole cities have deployed Wi-Fi networks for their users, and many users
never need to--- or never bother to--- use the wired network. With the advent of
high-throughput wireless networks (such as 802.11n) some new construction, even
of large enterprise build- ings, may no longer be wired for Ethernet. To understand
Internet traffic, then, we need to understand the wireless edge.
Measuring Wi-Fi traffic, however, is challenging. It is insufficient to capture
traffic in the access points, or upstream of the access points, because the activity
of neighboring networks, ad hoc networks, and physical interference cannot be seen
at that level. To truly understand the MAC-layer behavior, we need to capture frames
from the air using Air Monitors (AMs) placed in the vicinity of the network. Such
a capture is always a sample of the network activity, since it is physically impossible
to capture a full trace: all frames from all channels at all times in all places.
We have built a monitoring infrastructure that captures frames from the 802.11 network.
This infrastructure includes several "channel sampling" strategies that will capture
repre- sentative traffic from the network. Further, the monitoring infrastructure
needs to modify its behavior according to feedback received from the downstream
consumers of the captured traffic in case the analysis needs traffic of a certain
type. We call this technique "refocusing". The "coordinated sampling" technique
improves the efficiency of the monitoring by utilizing the AMs intelligently.
Finally, we deployed this measurement infrastructure within our Computer Science
building to study the performance of the system with real network traffic.
}
comment = {
Ph.D Dissertation. Advisor: David Kotz. Thesis Committee. David Kotz, Andrew Campbell,
Chris Bailey-Kellogg, Brian Noble.
}
}
@TechReport{Dartmouth:TR2008-619,
author = {Soumendra Nanda },
title = {{Mesh-Mon: a Monitoring and Management System for Wireless Mesh Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-619},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/468/TR2008-619.pdf},
abstract = {
A mesh network is a network of wireless routers that employ multi-hop routing and
can be used to provide network access for mobile clients. Mobile mesh networks can
be deployed rapidly to provide an alternate communication infrastructure for emergency
response operations in areas with limited or damaged infrastructure. In this dissertation,
we present Dart-Mesh: a Linux-based layer-3 dual-radio two-tiered mesh network that
provides complete 802.11b coverage in the Sudikoff Lab for Computer Science at Dartmouth
College. We faced several challenges in building, testing, monitoring and managing
this network. These challenges motivated us to design and implement Mesh-Mon, a
network monitoring system to aid system administrators in the management of a mobile
mesh network. Mesh-Mon is a scalable, distributed and decentralized management system
in which mesh nodes cooperate in a proactive manner to help detect, diagnose and
resolve network problems automatically. Mesh-Mon is independent of the routing protocol
used by the mesh routing layer and can function even if the routing protocol fails.
We demonstrate this feature by running Mesh-Mon on two versions of Dart-Mesh, one
running on AODV (a reactive mesh routing protocol) and the second running on OLSR
(a proactive mesh routing protocol) in separate experiments. Mobility can cause
links to break, leading to disconnected partitions. We identify critical nodes in
the network, whose failure may cause a partition. We introduce two new metrics based
on social-network analysis: the Localized Bridging Centrality (LBC) metric and the
Localized Load-aware Bridging Centrality (LLBC) metric, that can identify critical
nodes efficiently and in a fully distributed manner. We run a monitoring component
on client nodes, called Mesh-Mon-Ami, which also assists Mesh-Mon nodes in the dissemination
of management information between physically disconnected partitions, by acting
as carriers for management data.
We conclude, from our experimental evaluation on our 16-node Dart-Mesh testbed,
that our system solves several management challenges in a scalable manner, and is
a useful and effective tool for monitoring and managing real-world mesh networks.
}
comment = {
PhD Thesis. Advisor: David Kotz. Examining Committee: David Kotz, Andrew Campbell,
Robert L. Drysdale, Robert S. Gray.
}
}
@TechReport{Dartmouth:TR2008-618,
author = {Vibhor Bhatt and Nicholas Christman and Prasad Jayanti },
title = {{The Weakest Failure Detector to Solve Mutual Exclusion}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-618},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/467/TR2008-618.pdf},
abstract = {
Mutual exclusion is not solvable in an asynchronous message-passing system where
processes are subject to crash failures. Delporte-Gallet et. al. determined the
weakest failure detector to solve this problem when a majority of processes are
correct. Here we identify the weakest failure detector to solve mutual exclusion
in any environment, i.e., regardless of the number of faulty processes.
We also show a relation between mutual exclusion and consensus, arguably the two
most fundamental problems in distributed computing. Specifically, we show that a
failure detector that solves mutual exclusion is sufficient to solve non-uniform
consensus but not necessarily uniform consensus.
}
}
@TechReport{Dartmouth:TR2008-617,
author = {Patrick P. Tsang and Sean W. Smith },
title = {{YASIR: A Low-Latency, High-Integrity Security Retrofit for Legacy SCADA Systems (Extended Version)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-617},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/466/TR2008-617.pdf},
abstract = {
We construct a bump-in-the-wire (BITW) solution that retrofits security into time-critical
communications over bandwidth-limited serial links between devices in legacy Supervisory
Control And Data Acquisition (SCADA) systems, on which the proper operations of
critical infrastructures such as the electric power grid rely. Previous BITW solutions
do not provide the necessary security within timing constraints; the previous solution
that does is not BITW. At a hardware cost comparable to existing solutions, our
BITW solution provides sufficient security, and yet incurs minimal end-to-end communication
latency.
}
comment = {
This technical report is the extended version of the paper to appear in IFIP SEC
2008 under the same title. An earlier version of the paper appeared as Dartmouth
Computer Science Technical Report TR2007-603.
}
}
@TechReport{Dartmouth:TR2008-616,
author = {Chien-Chung Huang and Kavitha Telikepalli and Dimitrios Michail and Meghana Nasre },
title = {{Bounded Unpopularity Matchings}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-616},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/465/TR2008-616.pdf},
abstract = {
We investigate the following problem: given a set of jobs and a set of people with
preferences over the jobs, what is the optimal way of matching people to jobs? Here
we consider the notion of emph{popularity}. A matching $M$ is popular if there is
no matching $M'$ such that more people prefer $M'$ to $M$ than the other way around.
Determining whether a given instance admits a popular matching and, if so, finding
one, was studied in cite{AIKM05}. If there is no popular matching, a reasonable
substitute is a matching whose {em unpopularity} is bounded. We consider two measures
of unpopularity - {em unpopularity factor} denoted by $u(M)$ and {em unpopularity
margin} denoted by $g(M)$. McCutchen recently showed that computing a matching $M$
with the minimum value of $u(M)$ or $g(M)$ is NP-hard, and that if $G$ does not
admit a popular matching, then we have $u(M) ge 2$ for all matchings $M$ in $G$.
Here we show that a matching $M$ that achieves $u(M) = 2$ can be computed in $O(msqrt{n})$
time (where $m$ is the number of edges in $G$ and $n$ is the number of nodes) provided
a certain graph $H$ admits a matching that matches all people. We also describe
a sequence of graphs: $H = H_2, H_3,ldots,H_k$ such that if $H_k$ admits a matching
that matches all people, then we can compute in $O(kmsqrt{n})$ time a matching $M$
such that $u(M) le k-1$ and $g(M) le n(1-frac{2}{k})$. Simulation results suggest
that our algorithm finds a matching with low unpopularity.
}
}
@TechReport{Dartmouth:TR2008-615,
author = {Patrick P. Tsang and Sean W. Smith },
title = {{PPAA: Peer-to-Peer Anonymous Authentication (Extended Version)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-615},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/464/TR2008-615.pdf},
abstract = {
In the pursuit of authentication schemes that balance user privacy and accountability,
numerous anonymous credential systems have been constructed. However, existing systems
assume a client-server architecture in which only the clients, but not the servers,
care about their privacy. In peer-to-peer (P2P) systems where both clients and servers
are peer users with privacy concerns, no existing system correctly strikes that
balance between privacy and accountability. In this paper, we provide this missing
piece: a credential system in which peers are {em pseudonymous} to one another (that
is, two who interact more than once can recognize each other via pseudonyms) but
are otherwise anonymous and unlinkable across different peers. Such a credential
system finds applications in, e.g., Vehicular Ad-hoc Networks (VANets) and P2P networks.
We formalize the security requirements of our proposed credential system, provide
a construction for it, and prove the security of our construction. Our solution
is efficient: its complexities are independent of the number of users in the system.
}
comment = {
This technical report is the extended version of the paper to appear in ACNS '08
under the same title.
}
}
@TechReport{Dartmouth:TR2008-614,
author = {Xiaoduan Ye },
title = {{Experiment Planning for Protein Structure Elucidation and Site-Directed Protein Recombination}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-614},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/463/TR2008-614.pdf},
abstract = {
In order to most effectively investigate protein structure and improve protein function,
it is necessary to carefully plan appropriate experiments. The combinatorial number
of possible experiment plans demands effective criteria and efficient algorithms
to choose the one that is in some sense optimal. This thesis addresses experiment
planning challenges in two significant applications. The first part of this thesis
develops an integrated computational-experimental approach for rapid discrimination
of predicted protein structure models by quantifying their consistency with relatively
cheap and easy experiments (cross-linking and site-directed mutagenesis followed
by stability measurement). In order to obtain the most information from noisy and
sparse experimental data, rigorous Bayesian frameworks have been developed to analyze
the information content. Efficient algorithms have been developed to choose the
most informative, least expensive, and most robust experiments. The effectiveness
of this approach has been demonstrated using existing experimental data as well
as simulations, and it has been applied to discriminate predicted structure models
of the pTfa chaperone protein from bacteriophage lambda.
The second part of this thesis seeks to choose optimal breakpoint locations for
protein engineering by site-directed recombination. In order to increase the possibility
of obtaining folded and functional hybrids in protein recombination, it is necessary
to retain the evolutionary relationships among amino acids that determine protein
stability and functionality. A probabilistic hypergraph model has been developed
to model these relationships, with edge weights representing their statistical significance
derived from database and a protein family. The effectiveness of this model has
been validated by showing its ability to distinguish functional hybrids from non-functional
ones in existing experimental data. It has been proved to be NP-hard in general
to choose the optimal breakpoint locations for recombination that minimize the total
perturbation to these relationships, but exact and approximate algorithms have been
developed for a number of important cases.
}
comment = {
Ph.D thesis; Advisor Chris Bailey-Kellogg.
}
}
@TechReport{Dartmouth:TR2008-613,
author = {Shobha Potluri },
title = {{Complete Configuration Space Analysis for Structure Determination of Symmetric Homo-oligomers by NMR}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-613},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/462/TR2008-613.pdf},
abstract = {
Symmetric homo-oligomers (protein complexes with similar subunits arranged symmetrically)
play pivotal roles in complex biological processes such as ion transport and cellular
regulation. Structure determination of these complexes is necessary in order to
gain valuable insights into their mechanisms. Nuclear Magnetic Resonance (NMR) spectroscopy
is an experimental technique used for structural studies of such complexes. The
data available for structure determination of symmetric homo-oligomers by NMR is
often sparse and ambiguous in nature, raising concerns about existing heuristic
approaches for structure determination. We have developed an approach that is complete
in that it identifies all consistent conformations, data-driven in that it separately
evaluates the consistency of structures to data and biophysical constraints and
efficient in that it avoids explicit consideration of each of the possible structures
separately. By being complete, we ensure that native conformations are not missed.
By being data-driven, we are able to separately quantify the information content
in the data alone versus data and biophysical modeling. We take a configuration
space (degree-of-freedom) approach that provides a compact representation of the
conformation space and enables us to efficiently explore the space of possible conformations.
This thesis demonstrates that the configuration space-based method is robust to
sparsity and ambiguity in the data and enables complete, data-driven and efficient
structure determination of symmetric homo-oligomers.
}
comment = {
Ph.D thesis, completed in March 2007. Filed as a tech report February 2008. Advisor:
Chris Bailey-Kellogg.
}
}
@TechReport{Dartmouth:TR2008-612,
author = {Soumendra Nanda and David Kotz },
title = {{Localized Bridging Centrality for Distributed Network Analysis}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-612},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/461/TR2008-612.pdf},
abstract = {
Centrality is a concept often used in social network analysis to study different
properties of networks that are modeled as graphs. We present a new centrality metric
called Localized Bridging Centrality (LBC). LBC is based on the Bridging Centrality
(BC) metric that Hwang et al. recently introduced. Bridging nodes are nodes that
are located in between highly connected regions. LBC is capable of identifying bridging
nodes with an accuracy comparable to that of the BC metric for most networks. As
the name suggests, we use only local information from surrounding nodes to compute
the LBC metric, while, global knowledge is required to calculate the BC metric.
The main difference between LBC and BC is that LBC uses the egocentric definition
of betweenness centrality to identify bridging nodes, while BC uses the sociocentric
definition of betweenness centrality. Thus, our LBC metric is suitable for distributed
computation and has the benefit of being an order of magnitude faster to calculate
in computational complexity. We compare the results produced by BC and LBC in three
examples. We applied our LBC metric for network analysis of a real wireless mesh
network. Our results indicate that the LBC metric is as powerful as the BC metric
at identifying bridging nodes that have a higher flow of information through them
(assuming a uniform distribution of network flows) and are important for the robustness
of the network.
}
}
@TechReport{Dartmouth:TR2008-611,
author = {Libo Song },
title = {{Evaluating Mobility Predictors in Wireless Networks for Improving Handoff and Opportunistic Routing}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-611},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/460/TR2008-611.pdf},
abstract = {
We evaluate mobility predictors in wireless networks. Handoff prediction in wireless
networks has long been considered as a mechanism to improve the quality of service
provided to mobile wireless users. Most prior studies, however, were based on theoretical
analysis, simulation with synthetic mobility models, or small wireless network traces.
We study the effect of mobility prediction for a large realistic wireless situation.
We tackle the problem by using traces collected from a large production wireless
network to evaluate several major families of handoff-location prediction techniques,
a set of handoff-time predictors, and a predictor that jointly predicts handoff
location and time. We also propose a fallback mechanism, which uses a lower-order
predictor whenever a higher-order predictor fails to predict.
We found that low-order Markov predictors, with our proposed fallback mechanisms,
performed as well or better than the more complex and more space-consuming compression-based
handoff-location predictors. Although our handoff-time predictor had modest prediction
accuracy, in the context of mobile voice applications we found that bandwidth reservation
strategies can benefit from the combined location and time handoff predictor, significantly
reducing the call-drop rate without significantly increasing the call-block rate.
We also developed a prediction-based routing protocol for mobile opportunistic networks.
We evaluated and compared our protocol's performance to five existing routing protocols,
using simulations driven by real mobility traces. We found that the basic routing
protocols are not practical for large-scale opportunistic networks. Prediction-based
routing protocols trade off the message delivery ratio against resource usage and
performed well and comparable to each other.
}
comment = {
Ph.D dissertation. Advisor: David Kotz
}
}
@TechReport{Dartmouth:TR2008-610,
author = {Sergey Bratus and Cory Cornelius and Daniel Peebles and David Kotz },
title = {{Active Behavioral Fingerprinting of Wireless Devices}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-610},
year = {2008},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/459/TR2008-610.pdf},
abstract = {
We propose a simple active method for discovering facts about the chipset, the firmware
or the driver of an 802.11 wireless device by observing its responses (or lack thereof)
to a series of crafted non-standard or malformed 802.11 frames. We demonstrate that
such responses can differ significantly enough to distinguish between a number of
popular chipsets and drivers. We expect to significantly expand the number of recognized
device types through community contributions of signature data for the proposed
open fingerprinting framework. Our method complements known fingerprinting approaches,
and can be used to interrogate and spot devices that may be spoofing their MAC addresses
in order to conceal their true architecture from other stations, such as a fake
AP seeking to engage clients in complex protocol frame exchange (e.g., in order
to exploit a driver vulnerability). In particular, it can be used to distinguish
rogue APs from legitimate APs before association.
}
comment = {
Short version presented at WiSec 2008, Alexandria, VA
}
}
@TechReport{Dartmouth:TR2008-609,
author = {Anna M. Shubina },
title = {{Settling for limited privacy: how much does it help?}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2008-609},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/458/TR2008-609.pdf},
abstract = {
This thesis explores practical and theoretical aspects of several privacy-providing
technologies, including tools for anonymous web-browsing, verifiable electronic
voting schemes, and private information retrieval from databases. State-of-art privacy-providing
schemes are frequently impractical for implementational reasons or for sheer information-theoretical
reasons due to the amount of information that needs to be transmitted. We have been
researching the question of whether relaxing the requirements on such schemes, in
particular settling for imperfect but sufficient in real-world situations privacy,
as opposed to perfect privacy, may be helpful in producing more practical or more
efficient schemes. This thesis presents three results. The first result is the
introduction of caching as a technique for providing anonymous web-browsing at the
cost of sacrificing some functionality provided by anonymizing systems that do not
use caching. The second result is a coercion-resistant electronic voting scheme
with nearly perfect privacy and nearly perfect voter verifiability. The third result
consists of some lower bounds and some simple upper bounds on the amount of communication
in nearly private information retrieval schemes; our work is the first in-depth
exploration of private information schemes with imperfect privacy.
}
comment = {
Ph.D dissertation. Advisor: Amit Chakrabarti.
}
}
@TechReport{Dartmouth:TR2007-608,
author = {Yih-Kuen Tsay and Chien-Chung Huang },
title = {{Exclusion and Object Tracking in a Network of Processes}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-608},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/457/TR2007-608.pdf},
abstract = {
This paper concerns two fundamental problems in distributed computing---mutual exclusion
and mobile object tracking. For a variant of the mutual exclusion problem where
the network topology is taken into account, all existing distributed solutions make
use of tokens. It turns out that these token-based solutions for mutual exclusion
can also be adapted for object tracking, as the token behaves very much like a mobile
object. To handle objects with replication, we go further to consider the more general
$k$-exclusion problem which has not been as well studied in a network setting. A
strong fairness property for $k$-exclusion requires that a process trying to enter
the critical section will eventually succeed even if emph{up to} $k-1$ processes
stay in the critical section indefinitely. We present a comparative survey of existing
token-based mutual exclusion algorithms, which have provided much inspiration for
later $k$-exclusion algorithms. We then propose two solutions to the $k$-exclusion
problem, the second of which meets the strong fairness requirement. Fault-tolerance
issues are also discussed along with the suggestion of a third algorithm that is
also strongly fair. Performances of the three algorithms are compared by simulation.
Finally, we show how the various exclusion algorithms can be adapted for tracking
mobile objects.
}
}
@TechReport{Dartmouth:TR2007-606,
author = {Denise Anthony and Sean W. Smith and Tim Williamson },
title = {{The Quality of Open Source Production: Zealots and Good Samaritans in the Case of Wikipedia}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-606},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/456/TR2007-606.pdf},
abstract = {
New forms of production based in electronic technology, such as open-source and open-content
production, convert private commodities (typically software) into essentially public
goods. A number of studies find that, like in other collective goods, incentives
for reputation and group identity motivate contributions to open source goods, thereby
overcoming the social dilemma inherent in producing such goods. In this paper we
examine how contributor motivations affect the quality of contributions to the open-content
online encyclopedia Wikipedia. We find that quality is associated with contributor
motivations, but in a surprisingly inconsistent way. Registered users' quality increases
with more contributions, consistent with the idea of participants motivated by reputation
and commitment to the Wikipedia community. Surprisingly, however, we find the highest
quality from the vast numbers of anonymous "Good Samaritans" who contribute only
once. Our findings that Good Samaritans as well as committed "zealots" contribute
high quality content to Wikipedia suggest that it is the quantity as well as the
quality of contributors that positively affects the quality of open source production.
}
comment = {
A preliminary version of this paper was published online in November 2005.
}
}
@TechReport{Dartmouth:TR2007-605,
author = {Hany Farid and Jeffrey B. Woodward },
title = {{Video Stabilization and Enhancement}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-605},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/455/TR2007-605.pdf},
abstract = {
We describe a simple and computationally efficient approach for video stabilization
and enhancement. By combining multiple low-quality video frames, it is possible
to extract a high-quality still image. This technique is particularly helpful in
identifying people, license plates, etc. from low-quality video surveillance cameras.
}
}
@TechReport{Dartmouth:TR2007-603,
author = {Patrick P. Tsang and Sean W. Smith },
title = {{YASIR: A Low-Latency, High-Integrity Security Retrofit for Legacy SCADA Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-603},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/454/TR2007-603.pdf},
abstract = {
We construct a bump-in-the-wire (BITW) solution that retrofits security into time-critical
communications over bandwidth-limited serial links between devices in Supervisory
Control And Data Acquisition (SCADA) systems. Previous BITW solutions fail to provide
the necessary security within timing constraints; the previous solution that does
provide the necessary security is not BITW. At a comparable hardware cost, our BITW
solution provides sufficient security, and yet incurs minimal end-to-end communication
latency. A microcontroller prototype of our solution is under development.
}
comment = {
Updated as TR2008-617. You can find it here.
}
}
@TechReport{Dartmouth:TR2007-602,
author = {Richard Cole and Lisa Fleischer },
title = {{Fast-Converging Tatonnement Algorithms for the Market Problem}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-602},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/453/TR2007-602.pdf},
abstract = {
Why might markets tend toward and remain near equilibrium prices? In an effort to
shed light on this question from an algorithmic perspective, this paper defines
and analyzes two simple tatonnement algorithms that differ from previous algorithms
that have been subject to asymptotic analysis in three significant respects: the
price update for a good depends only on the price, demand, and supply for that good,
and on no other information; the price update for each good occurs distributively
and asynchronously; the algorithms work (and the analyses hold) from an arbitrary
starting point.
Our algorithm introduces a new and natural update rule. We show that this update
rule leads to fast convergence toward equilibrium prices in a broad class of markets
that satisfy the weak gross substitutes property. These are the first analyses for
computationally and informationally distributed algorithms that demonstrate polynomial
convergence.
Our analysis identifies three parameters characterizing the markets, which govern
the rate of convergence of our protocols. These parameters are, broadly speaking:
1. A bound on the fractional rate of change of demand for each good with respect
to fractional changes in its price.
2. A bound on the fractional rate of change of demand for each good with respect
to fractional changes in wealth.
3. The relative demand for money at equilibrium prices.
We give two protocols. The first assumes global knowledge of only the first parameter.
For this protocol, we also provide a matching lower bound in terms of these parameters.
Our second protocol assumes no global knowledge whatsoever.
}
}
@TechReport{Dartmouth:TR2007-601,
author = {Patrick P. Tsang and Man Ho Au and Apu Kapadia and Sean W. Smith },
title = {{Blacklistable Anonymous Credentials: Blocking Misbehaving Users without TTPs (Extended Version)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-601},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/452/TR2007-601.pdf},
abstract = {
Several credential systems have been proposed in which users can authenticate to
services anonymously. Since anonymity can give users the license to misbehave, some
variants allow the selective deanonymization (or linking) of misbehaving users upon
a complaint to a trusted third party (TTP). The ability of the TTP to revoke a user's
privacy at any time, however, is too strong a punishment for misbehavior. To limit
the scope of deanonymization, systems such as ``e-cash'' have been proposed in which
users are deanonymized under only certain types of well-defined misbehavior such
as ``double spending.'' While useful in some applications, it is not possible to
generalize such techniques to more subjective definitions of misbehavior. We present
the first anonymous credential system in which services can ``blacklist'' misbehaving
users without contacting a TTP. Since blacklisted users remain anonymous, misbehaviors
can be judged subjectively without users fearing arbitrary deanonymization by a
TTP.
}
comment = {
This technical report is the extended version of the paper to appear in CCS '07 under
the same title.
}
}
@TechReport{Dartmouth:TR2007-600,
author = {William B. Kerr and Fabio Pellacini },
title = {{Light-Based Sample Reduction Methods for Interactive Relighting of Scenes with Minute Geometric Scale}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-600},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/451/TR2007-600.pdf},
abstract = {
Rendering production-quality cinematic scenes requires high computational and temporal
costs. From an artist's perspective, one must wait for several hours for feedback
on even minute changes of light positions and parameters. Previous work approximates
scenes so that adjustments on lights may be carried out with interactive feedback,
so long as geometry and materials remain constant. We build on these methods by
proposing means by which objects with high geometric complexity at the subpixel
level, such as hair and foliage, can be approximated for real-time cinematic relighting.
Our methods make no assumptions about the geometry or shaders in a scene, and as
such are fully generalized. We show that clustering techniques can greatly reduce
multisampling, while still maintaining image fidelity at an error significantly
lower than sparsely sampling without clustering, provided that no shadows are computed.
Scenes that produce noise-like shadow patterns when sparse shadow samples are taken
suffer from additional error introduced by those shadows. We present a viable solution
to scalable scene approximation for lower sampling reolutions, provided a robust
solution to shadow approximation for sub-pixel geomery can be provided in the future.
}
}
@TechReport{Dartmouth:TR2007-598,
author = {Chien-Chung Huang },
title = {{Two's Company, Three's a Crowd: Stable Family and Threesome Roommates Problems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-598},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/450/TR2007-598.pdf},
abstract = {
We investigate Knuth's eleventh open question on stable matchings. In the stable
family problem, sets of women, men, and dogs are given, all of whom state their
preferences among the other two groups. The goal is to organize them into family
units, so that no three of them have the incentive to desert their assigned family
members to form a new family. A similar problem, called the threesome roommates
problem, assumes that a group of persons, each with their preferences among the
combinations of two others, are to be partitioned into triples. Similarly, the goal
is to make sure that no three persons want to break up with their assigned roommates.
Ng and Hirschberg were the first to investigate these two problems. In their formulation,
each participant provides a strictly-ordered list of all combinations. They proved
that under this scheme, both problems are NP-complete. Their paper reviewers pointed
out that their reduction exploits emph{inconsistent} preference lists and they wonder
whether these two problems remain NP-complete if preferences are required to be
consistent. We answer in the affirmative. In order to give these two problems a
broader outlook, we also consider the possibility that participants can express
indifference, on the condition that the preference consistency has to be maintained.
As an example, we propose a scheme in which all participants submit two (or just
one in the roommates case) lists ranking the other two groups separately. The order
of the combinations is decided by the sum of their ordinal numbers. Combinations
are tied when the sums are equal. By introducing indifference, a hierarchy of stabilities
can be defined. We prove that all stability definitions lead to NP-completeness
for existence of a stable matching.
}
}
@TechReport{Dartmouth:TR2007-597,
author = {Evan R. Sparks },
title = {{A Security Assessment of Trusted Platform Modules}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-597},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/449/TR2007-597.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/449/TR2007-597.pdf},
abstract = {
Trusted Platform Modules (TPMs) are becoming ubiquitous devices included in newly
released personal computers. Broadly speaking, the aim of this technology is to
provide a facility for authenticating the platform on which they are running: they
are able to measure attest to the authenticity of a hardware and software configuration.
Designed to be cheap, commodity devices which motherboard and processor vendors
can include in their products with minimal marginal cost, these devices have a good
theoretical design. Unfortunately, there exist several practical constraints on
the effectiveness of TPMs and the architectures which employ them which leave them
open to attack. We demonstrate some hardware and software attacks against these
devices and architectures. These attacks include Time of Check/Time of Use attacks
on the Integrity Measurment Architecture, and a bus attack against the Low Pin Count
bus. Further, we explore the possibility of side-channel attacks against TPMs.
}
comment = {
Senior Honors Thesis. Advisor: Sean Smith.
}
}
@TechReport{Dartmouth:TR2007-596,
author = {Thomas H. Cormen and Priya Natarajan and Elena Riccio Davidson },
title = {{When One Pipeline Is Not Enough}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-596},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/448/TR2007-596.pdf},
abstract = {
Pipelines that operate on buffers often work well to mitigate the high latency inherent
in interprocessor communication and in accessing data on disk. Running a single
pipeline on each node works well when each pipeline stage consumes and produces
data at the same rate. If a stage might consume data faster or slower than it produces
data, a single pipeline becomes unwieldy.
We describe how we have extended the FG programming environment to support multiple
pipelines in two forms. When a node might send and receive data at different rates
during interprocessor communication, we use disjoint pipelines that send and receive
on each node. When a node consumes and produces data from different streams on the
node, we use multiple pipelines that intersect at a particular stage. Experimental
results for two out-of-core sorting algorithms---one based on columnsort and the
other a distribution-based sort---demonstrate the value of multiple pipelines.
}
}
@TechReport{Dartmouth:TR2007-594,
author = {Nihal A. D'Cunha },
title = {{Exploring the Integration of Memory Management and Trusted Computing}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-594},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/447/TR2007-594.pdf},
abstract = {
This thesis addresses vulnerabilities in current Trusted Computing architecture by
exploring a design for a better Trusted Platform Module (TPM); one that integrates
more closely with the CPU's Memory Management Unit (MMU). We establish that software-based
attacks on trusted memory can be carried out undetectably by an adversary on current
TCG/TPM implementations. We demonstrate that an attacker with sufficient privileges
can compromise the integrity of a TPM-protected system by modifying critical loaded
code and static data after measurement has taken place. More specifically, these
attacks illustrate the Time Of Check vs. Time of Use (TOCTOU) class of attacks.
We propose to enhance the MMU, enabling it to detect when memory containing trusted
code or data is being maliciously modified at run-time. On detection, it should
be able to notify the TPM of these modifications. We seek to use the concepts of
selective memory immutability as a security tool to harden the MMU, which will result
in a more robust TCG/TPM implementation. To substantiate our ideas for this proposed
hardware feature, we designed and implemented a software prototype system, which
employs the monitoring capabilities of the Xen virtual machine monitor.
We performed a security evaluation of our prototype and validated that it can detect
all our software-based TOCTOU attacks. We applied our prototype to verify the integrity
of data associated with an application, as well as suggested and implemented ways
to prevent unauthorized use of data by associating it with its owner process. Our
performance evaluation reveals minimal overhead.
}
comment = {
M.S. Thesis. Advisor: Sean Smith.
}
}
@TechReport{Dartmouth:TR2007-593,
author = {Mark C. Henle },
title = {{Closest and Farthest-Line Voronoi Diagrams in the Plane}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-593},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/446/TR2007-593.pdf},
abstract = {
Voronoi diagrams are a geometric structure containing proximity information useful
in efficiently answering a number of common geometric problems associated with a
set of points in the plane.. They have applications in fields ranging from crystallography
to biology. Diagrams of sites other than points and with different distance metrics
have been studied. This paper examines the Voronoi diagram of a set of lines, which
has escaped study in the computational geometry literature.
The combinatorial and topological properties of the closest and farthest Voronoi
diagrams are analyzed and O(n^2) and O(n log n) algorithms are presented for their
computation respectively.
}
comment = {
Senior Honors Thesis. Advisor: Robert L. Scot Drysdale
}
}
@TechReport{Dartmouth:TR2007-592,
author = {Daniel G. Peebles },
title = {{SCML: A Structural Representation for Chinese Characters}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-592},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/445/TR2007-592.pdf},
abstract = {
Chinese characters are used daily by well over a billion people. They constitute
the main writing system of China and Taiwan, form a major part of written Japanese,
and are also used in South Korea. Anything more than a cursory glance at these characters
will reveal a high degree of structure to them, but computing systems do not currently
have a means to operate on this structure. Existing character databases and dictionaries
treat them as numerical code points, and associate with them additional `hand-computed'
data, such as stroke count, stroke order, and other information to aid in specific
searches. Searching by a character's `shape' is effectively impossible in these
systems.
I propose a new approach to representing these characters, through an XML-based
language called SCML. This language, by encoding an abstract form of a character,
allows the direct retrieval of important information such as stroke count and stroke
order, and permits useful but previously impossible automated analysis of characters.
In addition, the system allows the design of a view that takes abstract SCML representations
as character models and outputs glyphs based on an aesthetic, facilitating the creation
of `meta-fonts' for Chinese characters. Finally, through the creation of a specialized
database, SCML allows for efficient structural character queries to be performed
against the body of inserted characters, thus allowing people to search by the most
obvious of a character's characteristics: its shape.
}
comment = {
Senior Honors Thesis. Advisor: Devin Balkcom.
}
}
@TechReport{Dartmouth:TR2007-591,
author = {Kwang-Hyun Baek and Sergey Bratus and Sara Sinclair and Sean W. Smith },
title = {{Dumbots: Unexpected Botnets through Networked Embedded Devices}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-591},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/444/TR2007-591.pdf},
abstract = {
Currently, work on botnets focuses primarily on PCs. However, as lightweight computing
devices with embedded operating systems become more ubiquitous, they present a new
and very disturbing target for botnet developers. In this paper, we present both
an empirical demonstration on a widely deployed multimedia box, as well as an evaluation
of the deeper potential of these dumbots.
}
}
@TechReport{Dartmouth:TR2007-590,
author = {Patrick P. Tsang and Sean W. Smith },
title = {{Secure Cryptographic Precomputation with Insecure Memory}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-590},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/443/TR2007-590.pdf},
abstract = {
Precomputation dramatically reduces the execution latency of many cryptographic algorithms.
To sustain the reduced latency over time during which these algorithms are routinely
invoked, however, a pool of precomputation results must be stored and be readily
available. While precomputation is an old and well-known technique, how to securely
and yet efficiently store these precomputation results has largely been ignored.
For instance, requiring tamper-proof memory would be too expensive, if not unrealistic,
for precomputation to be cost-effective. In this paper, we propose an architecture
that provides secure storage for cryptographic precomputation using only insecure
memory, which may be eavesdropped or even tampered with. Specifically, we design
a small tamper-resistant hardware module that we call the {em Queue Security Proxy
(QSP)}, which situates on the data-path between the processor and the insecure memory.
Our analysis shows that our design is secure, efficient, flexible and yet inexpensive.
In particular, our design's timing overhead and hardware cost are independent of
the storage size. We also discuss in this paper several interesting extensions to
our proposed architecture. We plan to prototype our design assuming the scenario
of precomputing DSA signatures, effectively building a cost-effective low-latency
DSA signing secure coprocessor.
}
}
@TechReport{Dartmouth:TR2007-589,
author = {Alexander Wakefield Steinberg },
title = {{Lighting with Sketches}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-589},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/442/TR2007-589.pdf},
abstract = {
Lighting design is a fundamental aspect of computer cinematography, where it is used
to support storytelling by affecting the mood, style, and believability of a scene.
Traditionally, lighting has requred the tedious adjustment of large set parameters
that describe complex lighting setups, including lights positions, colors, shapes,
etc. This work presents an interactive user interface that facilitates lighting
workflow by using a sketching paradigm for light creation. Lights are specified
by a series of strokes that define various properties of illumination such as shape
of the light and position of illuminated and shadowed areass. The system will them
perform a nonlinear optimization over all the light parameters to find a match to
the controlling sketches. To demonstrate our prototype system, we lit a simple scene
fully with our application, showing that sketching paradigms ar promising to facilitate
the lighting workflow.
}
comment = {
Advisor: Fabio Pellacini
}
}
@TechReport{Dartmouth:TR2007-588,
author = {Soumendra Nanda and Zhenhui Jiang and David Kotz },
title = {{A Combined Routing Method for Wireless Ad Hoc Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-588},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/441/TR2007-588.pdf},
abstract = {
To make ad hoc wireless networks adaptive to different mobility and traffic patterns,
this paper proposes an approach to swap from one protocol to another protocol dynamically,
while routing continues. By the insertion of a thin new layer, we were able to make
each node in the ad hoc wireless network notify each other about the protocol swap.
To ensure that routing works efficiently after the protocol swap, we initialized
the destination routing protocol's data structures and reused the previous routing
information to build the new routing table. We also tested our approach under different
network topologies and traffic patterns in static networks to learn whether the
swap was fast and whether the swap incurred too much overhead. We found that the
swap latency was related to the nature of the destination protocol and the topology
of the network. We also found that the control packet ratio after swap was close
to that of the protocol running without swap, which indicates that our method does
not incur too much overhead for the swap.
}
comment = {
This report is superceded by TR2009-641; please see that report instead. This report
is a shortened and updated version of the M.S. thesis that appeared as TR2005-566.
}
}
@TechReport{Dartmouth:TR2007-587,
author = {John Thomas and Naren Ramakrishnan and Chris Bailey-Kellogg },
title = {{Protein Design by Mining and Sampling an Undirected Graphical Model of Evolutionary Constraints}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-587},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/440/TR2007-587.pdf},
abstract = {
Evolutionary pressures on proteins to maintain structure and function have constrained
their sequences over time and across species. The sequence record thus contains
valuable information regarding the acceptable variation and covariation of amino
acids in members of a protein family. When designing new members of a protein family,
with an eye toward modified or improved stability or functionality, it is incumbent
upon a protein engineer to uncover such constraints and design conforming sequences.
This paper develops such an approach for protein design: we first mine an undirected
probabilistic graphical model of a given protein family, and then use the model
generatively to sample new sequences. While sampling from an undirected model is
difficult in general, we present two complementary algorithms that effectively sample
the sequence space constrained by our protein family model. One algorithm focuses
on the high-likelihood regions of the space. Sequences are generated by sampling
the cliques in a graphical model according to their likelihood while maintaining
neighborhood consistency. The other algorithm designs a fixed number of high-likelihood
sequences that are reflective of the amino acid composition of the given family.
A set of shuffled sequences is iteratively improved so as to increase their mean
likelihood under the model. Tests for two important protein families, WW domains
and PDZ domains, show that both sampling methods converge quickly and generate diverse
high-quality sets of sequences for further biological study.
}
comment = {
Submitted to KDD 2007.
}
}
@TechReport{Dartmouth:TR2007-586,
author = {Peter Johnson and Apu Kapadia and David Kotz and Nikos Triandopoulos },
title = {{People-Centric Urban Sensing: Security Challenges for the New Paradigm}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2007-586},
year = {2007},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/439/TR2007-586.pdf},
abstract = {
We study the security challenges that arise in emph{people-centric urban sensing},
a new sensor-networking paradigm that leverages humans as part of the sensing infrastructure.
Most prior work on sensor networks has focused on collecting and processing ephemeral
data about the environment using a static topology and an application-aware infrastructure.
People-centric urban sensing, however, involves collecting, storing, processing
and fusing large volumes of data related to every-day human activities. Sensing
is performed in a highly dynamic and mobile environment, and supports (among other
things) pervasive computing applications that are focused on enhancing the user's
experience. In such a setting, where humans are the central focus, there are new
challenges for information security; not only because of the complex and dynamic
communication patterns, but also because the data originates from sensors that are
carried by a person---not a tiny sensor thrown in the forest or mounted on the neck
of an animal. In this paper we aim to instigate discussion about this critical issue---because
people-centric sensing will never succeed without adequate provisions for security
and privacy. To that end, we outline several important challenges and suggest general
solutions that hold promise in this new paradigm of sensor networks.
}
}
@TechReport{Dartmouth:TR2006-585,
author = {David P. Wagner },
title = {{Path Planning Algorithms under the Link-Distance Metric}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-585},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/438/TR2006-585.pdf},
abstract = {
The Traveling Salesman Problem and the Shortest Path Problem are famous problems
in computer science which have been well studied when the objective is measured
using the Euclidean distance. Here we examine these geometric problems under a different
set of optimization criteria. Rather than considering the total distance traversed
by a path, this thesis looks at reducing the number of times a turn is made along
that path, or equivalently, at reducing the number of straight lines in the path.
Minimizing this objective value, known as the link-distance, is useful in situations
where continuing in a given direction is cheap, while turning is a relatively expensive
operation. Applications exist in VLSI, robotics, wireless communications, space
travel, and other fields where it is desirable to reduce the number of turns.
This thesis examines rectilinear and non-rectilinear variants of the Traveling Salesman
Problem under this metric. The objective of these problems is to find a path visiting
a set of points which has the smallest number of bends. A 2-approximation algorithm
is given for the rectilinear problem, while for the non-rectilinear problem, an
O(log n)-approximation algorithm is given. The latter problem is also shown to be
NP-Complete.
Next, the Rectilinear Minimum Link-Distance Problem, also known as the Minimum Bends
Path Problem, is considered. Here the objective is to find a rectilinear path between
two points among rectilinear obstacles which has the minimum number of bends, while
avoiding passing through any of the obstacles. The problem has been well studied
in two dimensions, but is relatively unexplored in higher dimensions. A main result
of this thesis is an O(n^{5/2} log n) time algorithm solving this problem in three
dimensions. Previously known algorithms have had worst-case running times of Omega(n^3).
This algorithm requires a data structure that supports efficient operations on pointsets
within rectangular regions of the Euclidean plane. We design a new data structure,
which is a variation on the segment tree, in order to support these operations.
Finally, an implementation of the data structure and of the algorithm solving the
Minimum Link-Distance Problem demonstrates their experimental running times and
ease of implementation.
}
comment = {
Doctoral dissertation. Co-Advisors: Robert Scot Drysdale, Clifford Stein; Thesis
Committee: Amit Chakrabarti, Joseph S. B. Mitchell
}
}
@TechReport{Dartmouth:TR2006-584,
author = {Javed Aslam and Sergey Bratus and Virgil Pavlu },
title = {{Tools and algorithms to advance interactive intrusion analysis via Machine Learning and Information Retrieval}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-584},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/437/TR2006-584.pdf},
abstract = {
We consider typical tasks that arise in the intrusion analysis of log data from the
perspectives of Machine Learning and Information Retrieval, and we study a number
of data organization and interactive learning techniques to improve the analyst's
efficiency. In doing so, we attempt to translate intrusion analysis problems into
the language of the abovementioned disciplines and to offer metrics to evaluate
the effect of proposed techniques. The Kerf toolkit contains prototype implementations
of these techniques, as well as data transformation tools that help bridge the gap
between the real world log data formats and the ML and IR data models.
We also describe the log representation approach that Kerf prototype tools are based
on. In particular, we describe the connection between decision trees, automatic
classification algorithms and log analysis techniques implemented in Kerf.
}
}
@TechReport{Dartmouth:TR2006-583,
author = {Hany Farid },
title = {{Digital Image Ballistics from JPEG Quantization}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-583},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/436/TR2006-583.pdf},
abstract = {
Most digital cameras export images in the JPEG file format. This lossy compression
scheme employs a quantization table that controls the amount of compression achieved.
Different cameras typically employ different tables. A comparison of an image's
quantization scheme to a database of known cameras affords a simple technique for
confirming or denying an image's source. Similarly, comparison to a database of
photo-editing software can be used in a forensic setting to determine if an image
was edited after its original recording.
}
}
@TechReport{Dartmouth:TR2006-582,
author = {Chien-Chung Huang },
title = {{Cheating to Get Better Roommates in a Random Stable Matching}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-582},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/435/TR2006-582.pdf},
abstract = {
This paper addresses strategies for the stable roommates problem, assuming that a
stable matching is chosen at random. We investigate how a cheating man should permute
his preference list so that he has a higher-ranking roommate probabilistically.
In the first part of the paper, we identify a necessary condition for creating
a new stable roommate for the cheating man. This condition precludes any possibility
of his getting a new roommate ranking higher than all his stable roommates when
everyone is truthful. Generalizing to the case that multiple men collude, we derive
another impossibility result: given any stable matching in which a subset of men
get their best possible roommates, they cannot cheat to create a new stable matching
in which they all get strictly better roommates than in the given matching.
Our impossibility result, considered in the context of the stable marriage problem,
easily re-establishes the celebrated Dubins-Freedman Theorem. The more generalized
Demange-Gale-Sotomayor Theorem states that a coalition of men and women cannot cheat
to create a stable matching in which everyone of them gets a strictly better partner
than in the Gale-Shapley algorithm (with men proposing). We give a sharper result:
a coalition of men and women cannot cheat together so that, in a newly-created stable
matching, every man in the coalition gets a strictly better partner than in the
Gale-Shapley algorithm while none of the women in the coalition is worse off.
In the second part of the paper, we present two cheating strategies that guarantee
that the cheating man's new probability distribution over stable roommates majorizes
the original one. These two strategies do not require the knowledge of the probability
distribution of the cheating man. This is important because the problem of counting
stable matchings is #P-complete. Our strategies only require knowing the set of
stable roommates that the cheating man has and can be formulated in polynomial time.
Our second cheating strategy has an interesting corollary in the context of stable
marriage with the Gale-Shapley algorithm. Any woman-optimal strategy will ensure
that every woman, cheating or otherwise, ends up with a partner at least as good
as when everyone is truthful.
}
}
@TechReport{Dartmouth:TR2006-580,
author = {Fabio Pellacini and Lori Lorigo and Geri Gay },
title = {{Visualizing Paths in Context}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-580},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/434/TR2006-580.pdf},
abstract = {
Data about movement through a space is increasingly becoming available for capture
and analysis. In many applications, this data is captured or modeled as transitions
between a small number of areas of interests, or a finite set of states, and these
transitions constitute paths in the space. Similarities and differences between
paths are of great importance to such analyses, but can be difficult to assess.
In this work we present a visualization approach for representing paths in context,
where individual paths can be compared to other paths or to a group of paths. Our
approach summarizes path behavior using a simple circular layout, including information
about state and transition likelihood using Markov random models, together with
information about specific path and state behavior. The layout avoids line crossovers
entirely, making it easy to observe patterns while reducing visual clutter. In our
tool, paths can either be compared in their natural sequence or by aligning multiple
paths using Multiple Sequence Alignment, which can better highlight path similarities.
We applied our technique to eye tracking data and cell phone tower data used to
capture human movement.
}
}
@TechReport{Dartmouth:TR2006-579,
author = {Micah K. Johnson and Hany Farid },
title = {{Metric Measurements on a Plane from a Single Image}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-579},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/433/TR2006-579.pdf},
abstract = {
The past decade has seen considerable advances in the application of principles from
projective geometry to problems in image analysis and computer vision. In this paper,
we review a subset of this work, and leverage these results for the purpose of forensic
analysis. Specifically, we review three techniques for making metric measurements
on planar surfaces from a single image. The resulting techniques should prove useful
in forensic settings where real-world measurements are required.
}
}
@TechReport{Dartmouth:TR2006-578,
author = {Khanh Do Ba },
title = {{Wait-Free and Obstruction-Free Snapshot}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-578},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/432/TR2006-578.pdf},
abstract = {
The snapshot problem was first proposed over a decade ago and has since been well-studied
in the distributed algorithms community. The challenge is to design a data structure
consisting of $m$ components, shared by upto $n$ concurrent processes, that supports
two operations. The first, $Update(i,v)$, atomically writes $v$ to the $i$th component.
The second, $Scan()$, returns an atomic snapshot of all $m$ components. We consider
two termination properties: wait-freedom, which requires a process to always terminate
in a bounded number of its own steps, and the weaker obstruction-freedom, which
requires such termination only for processes that eventually execute uninterrupted.
First, we present a simple, time and space optimal, obstruction-free solution to
the single-writer, multi-scanner version of the snapshot problem (wherein concurrent
Updates never occur on the same component). Second, we assume hardware support for
compare&swap (CAS) to give a time-optimal, wait-free solution to the multi-writer,
single-scanner snapshot problem (wherein concurrent Scans never occur). This algorithm
uses only $O(mn)$ space and has optimal CAS, write and remote-reference complexities.
Additionally, it can be augmented to implement a general snapshot object with the
same time and space bounds, thus improving the space complexity of $O(mn^2)$ of
the only previously known time-optimal solution.
}
comment = {
Senior Honors Thesis. Advisor: Prasad Jayanti.
}
}
@TechReport{Dartmouth:TR2006-577,
author = {Constantinos C. Neophytou },
title = {{SAMPLED: Shared Anonymous Music PLayback using wirelEss Devices}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-577},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/431/TR2006-577.pdf},
abstract = {
Recent advances in mobile computing enable many new applications, yet at the same
time create privacy implications caused by the increasing amount of data that becomes
available. This thesis will explore the possibilities of wireless-enabled portable
devices and their attending privacy implications.
We will describe how such a device containing personal information about the musical
preferences of its user can help improve the user's experience in a social setting
where music is played for all, and at the same time preserve each user's privacy.
}
comment = {
Undergraduate project; advisor Tristan Henderson.
}
}
@TechReport{Dartmouth:TR2006-576,
author = {Anne Loomis },
title = {{Computation Reuse in Statics and Dynamics Problems for Assemblies of Rigid Bodies}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-576},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/430/TR2006-576.pdf},
abstract = {
The problem of determining the forces among contacting rigid bodies is fundamental
to many areas of robotics, including manipulation planning, control, and dynamic
simulation. For example, consider the question of how to unstack an assembly, or
how to find stable regions of a rubble pile. In considering problems of this type
over discrete or continuous time, we often encounter a sequence of problems with
similar substructure. The primary contribution of our work is the observation that
in many cases, common physical structure can be exploited to solve a sequence of
related problems more efficiently than if each problem were considered in isolation.
We examine three general problems concerning rigid-body assemblies: dynamic simulation,
assembly planning, and assembly stability given limited knowledge of the structure's
geometry.
To approach the dynamic simulation and assembly planning applications, we have
optimized a known method for solving the system dynamics. The accelerations of and
forces among contacting rigid bodies may be computed by formulating the dynamics
equations and contact constraints as a complementarity problem. Dantzig's algorithm,
when applicable, takes n or fewer major cycles to find a solution to the linear
complementarity problem corresponding to an assembly with n contacts. We show that
Dantzig's algorithm will find a solution in n - k or fewer major cycles if the algorithm
is initialized with a solution to the dynamics problem for a subassembly with k
internal contacts.
Finally, we show that if we have limited knowledge of a structure's geometry, we
can still learn about stable regions of its surface by physically pressing on it.
We present an approach for finding stable regions of planar assemblies: sample presses
on the surface to identify a stable cone in wrench space, partition the space of
applicable wrenches into stable and unstable regions, and map these back to the
surface of the structure.
}
comment = {
Master's thesis.
}
}
@TechReport{Dartmouth:TR2006-574,
author = {Nicholas J. Santos },
title = {{Limited Delegation (Without Sharing Secrets) in Web Applications}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-574},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/429/TR2006-574.pdf},
abstract = {
Delegation is the process wherein an entity Alice designates an entity Bob to speak
on her behalf. In password-based security systems, delegation is easy: Alice gives
Bob her password. This is a useful feature, and is used often in the real world.
But it's also problematic. When Alice shares her password, she must delegate all
her permissions, but she may wish to delegate a limited set. Also, as we move towards
PKI-based systems, secret-sharing becomes impractical. This thesis explores one
solution to these problems. We use proxy certificates in a non-standard way so that
user Alice can delegate a subset of her privileges to user Bob in a secure, decentralized
way for web applications.
We identify how delegation changes the semantics of access control, then build
a system to demonstrate these possibilities in action. An extension on top of Mozilla's
Firefox web browser allows a user to create and use proxy certificates for delegation,
and a module on top of the Apache web server accepts multiple chains of these certificates.
This is done in a modified SSL session that should not break current SSL implementations.
}
comment = {
Senior Honors Thesis. Advisor: Sean W. Smith.
}
}
@TechReport{Dartmouth:TR2006-573,
author = {Gregory Leibon and Dan Rockmore and Martin R. Pollak },
title = {{A simple computational method for the identification of disease-associated loci in complex, incomplete pedigrees}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-573},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/428/TR2006-573.pdf},
abstract = {
We present an approach, called the Shadow Method, for the identification of disease
loci from dense genetic marker maps in complex, potentially incomplete pedigrees.
Shadow is a simple method based on an analysis of the patterns of obligate meiotic
recombination events in genotypic data. This method can be applied to any high density
marker map and was specifically designed to explore the fact that extremely dense
marker maps are becoming more readily available. We also describe how to interpret
and associated meaningful P-Values to the results. Shadow has significant advantages
over traditional parametric linkage analysis methods in that it can be readily applied
even in cases in which the topology of a pedigree or pedigrees can only be partially
determined. In addition, Shadow is robust to variability in a range of parameters
and in particular does not require prior knowledge of mode of inheritance, penetrance,
or clinical misdiagnosis rate. Shadow can be used for any SNP data, but is especially
effective when applied to dense samplings. Our primary example uses data from Affymetrix
100k SNPChip samples in which we illustrate our approach by analyzing simulated
data as well as genome-wide SNP data from two pedigrees with inherited forms of
kidney failure, one of which is compared with a typical LOD score analysis.
}
}
@TechReport{Dartmouth:TR2006-571,
author = {Kazuhiro Minami },
title = {{Secure Context-sensitive Authorization}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-571},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/427/TR2006-571.pdf},
abstract = {
Pervasive computing leads to an increased integration between the real world and
the computational world, and many applications in pervasive computing adapt to the
user's context, such as the location of the user and relevant devices, the presence
of other people, light or sound conditions, or available network bandwidth, to meet
a user's continuously changing requirements without taking explicit input from the
users. We consider a class of applications that wish to consider a user's context
when deciding whether to authorize a user's access to important physical or information
resources. Such a context-sensitive authorization scheme is necessary when a mobile
user moves across multiple administrative domains where they are not registered
in advance. Also, users interacting with their environment need a non-intrusive
way to access resources, and clues about their context may be useful input into
authorization policies for these resources. Existing systems for context-sensitive
authorization take a logic-based approach, because a logical language makes it possible
to define a context model where a contextual fact is expressed with a boolean predicate
and to derive higher-level context information and authorization decisions from
contextual facts. However, those existing context-sensitive authorization systems
have a central server that collects context information, and evaluates policies
to make authorization decisions on behalf of a resource owner. A centralized solution
assumes that all resource owners trust the server to make correct decisions, and
all users trust the server not to disclose private context information. In many
realistic applications of pervasive computing, however, the resources, users, and
sources of context information are inherently distributed among many organizations
that do not necessarily trust each other. Resource owners may not trust the integrity
of context information produced by another domain, and context sensors may not trust
others with the confidentiality of data they provide about users. In this thesis,
we present a secure distributed proof system for context-sensitive authorization.
Our system enables multiple hosts to evaluate an authorization query in a peer-to-peer
way, while preserving the confidentiality and integrity policies of mutually untrusted
principals running those hosts. We also develop a novel caching and revocation mechanism
to support context-sensitive policies that refer to information in dozens of different
administrative domains. Contributions of this thesis include the definition of fine-grained
security policies that specify trust relations among principals in terms of information
confidentiality and integrity, the design and implementation of a secure distributed
proof system, a proof for the correctness of our algorithm, and a performance evaluation
showing that the amortized performance of our system scales to dozens of servers
in different domains.
}
comment = {
Doctoral dissertation. Advisor: David Kotz
}
}
@TechReport{Dartmouth:TR2006-570,
author = {Ivelin Georgiev and Ryan H. Lilien and Bruce R. Donald },
title = {{A Novel Minimized Dead-End Elimination Criterion and Its Application to Protein Redesign in a Hybrid Scoring and Search Algorithm for Computing Partition Functions over Molecular Ensembles}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2006-570},
year = {2006},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/426/TR2006-570.pdf},
abstract = {
Novel molecular function can be achieved by redesigning an enzyme's active site so
that it will perform its chemical reaction on a novel substrate. One of the main
challenges for protein redesign is the efficient evaluation of a combinatorial number
of candidate structures. The modeling of protein flexibility, typically by using
a rotamer library of commonly-observed low-energy side-chain conformations, further
increases the complexity of the redesign problem. A dominant algorithm for protein
redesign is Dead-End Elimination (DEE), which prunes the majority of candidate conformations
by eliminating rigid rotamers that provably are not part of the Global Minimum Energy
Conformation (GMEC). The identified GMEC consists of rigid rotamers (i.e., rotamers
that have not been energy-minimized) and is thus referred to as the rigid-GMEC.
As a post-processing step, the conformations that survive DEE may be energy-minimized.
When energy minimization is performed after pruning with DEE, the combined protein
design process becomes heuristic, and is no longer provably accurate: a conformation
that is pruned using rigid-rotamer energies may subsequently minimize to a lower
energy than the rigid-GMEC. That is, the rigid-GMEC and the conformation with the
lowest energy among all energy-minimized conformations (the minimized-GMEC) are
likely to be different. While the traditional DEE algorithm succeeds in not pruning
rotamers that are part of the rigid-GMEC, it makes no guarantees regarding the identification
of the minimized-GMEC. In this paper we derive a novel, provable, and efficient
DEE-like algorithm, called minimized-DEE (MinDEE), that guarantees that rotamers
belonging to the minimized-GMEC will not be pruned, while still pruning a combinatorial
number of conformations. We show that MinDEE is useful not only in identifying the
minimized-GMEC, but also as a filter in an ensemble-based scoring and search algorithm
for protein redesign that exploits energy-minimized conformations. We compare our
results both to our previous computational predictions of protein designs and to
biological activity assays of predicted protein mutants. Our provable and efficient
minimized-DEE algorithm is applicable in protein redesign, protein-ligand binding
prediction, and computer-aided drug design.
}
comment = {
A revised version of this paper will appear in the Proceedings of the Tenth Annual
International Conference on Research in Computational Molecular Biology (RECOMB),
Venice Lido, Italy, April 2006.
}
}
@TechReport{Dartmouth:TR2005-566,
author = {Zhenhui Jiang },
title = {{A Combined Routing Method for Ad hoc Wireless Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-566},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/425/TR2005-566.pdf},
abstract = {
To make ad hoc wireless networks adaptive to different mobility and traffic patterns,
we studied in this thesis an approach to swap from one protocol to another protocol
dynamically, while routing continues. By the insertion of a new layer, we were able
to make each node in the ad hoc wireless network notify each other about the protocol
swap. To ensure that routing works efficiently after the protocol swap, we initialized
the destination routing protocols data structures and reused the previous routing
information to build the new routing table. We also tested our approach under different
network topologies and traffic patterns in static networks to learn whether the
swap is fast and whether the swap incurs too much overload . We found that the swap
latency is related to the destination protocol and the topology of the network.
We also found that the control packet ratio after swap is close to the protocol
running without swap, which means our method does not incur too many control packets
for swap.
}
comment = {
Masters thesis. Advisor: David Kotz. A shortened and updated version of this work
appears as TR2007-588.
}
}
@TechReport{Dartmouth:TR2005-565,
author = {Chien-Chung Huang },
title = {{How hard is it to cheat in the Gale-Shapley Stable Matching Algorithm}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-565},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/424/TR2005-565.pdf},
abstract = {
We study strategy issues surrounding the stable marriage problem. Under the Gale-Shapley
algorithm (with men proposing), a classical theorem says that it is impossible for
every liar to get a better partner. We try to challenge this theorem. First, observing
a loophole in the statement of the theorem, we devise a coalition strategy in which
a non-empty subset of the liars gets a better partner and no man is worse off than
before. This strategy is restricted in that not everyone has the incentive to cheat.
We attack the classical theorem further by means of randomization. However, this
theorem shows surprising robustness: it is impossible that every liar has the chance
to improve while no one gets hurt. Hence, this impossibility result indicates that
it is always hard to induce some people to falsify their lists. Finally, to overcome
the problem of lacking motivation, we exhibit another randomized lying strategy
in which every liar can expect to get a better partner, though with a chance of
getting a worse one.
}
}
@TechReport{Dartmouth:TR2005-564,
author = {Bruce R. Donald and Christopher G. Levey and Craig D. McGray and Igor Paprotny and Daniela Rus },
title = {{A Steerable, Untethered, 250x60 micron MEMS Mobile Micro-Robot}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-564},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/423/TR2005-564.pdf},
abstract = {
We present a steerable, electrostatic, untethered, MEMS micro-robot, with dimensions
of 60 µm by 250 µm by 10 µm. This micro-robot is 1 to 2 orders
of magnitude smaller in size than previous micro-robotic systems. The device
consists of a curved, cantilevered steering arm, mounted on an untethered scratch
drive actuator. These two components are fabricated monolithically from the same
sheet of conductive polysilicon, and receive a common power and control signal through
a capacitive coupling with an underlying electrical grid. All locations on the grid
receive the same power and control signal, so that the devices can be operated without
knowledge of their position on the substrate and without constraining rails or tethers.
Control and power delivery waveforms are broadcast to the device through the capacitive
power coupling, and are decoded by the electromechanical response of the device
body. Individual control of the component actuators provides two distinct motion
gaits (forward motion and turning), which together allow full coverage of a planar
workspace (the robot is globally controllable). These MEMS micro-robots demonstrate
turning error of less than 3.7 °/mm during forward motion, turn with radii as
small as 176 µm, and achieve speeds of over 200 µm/sec, with an average
step size of 12 nm. They have been shown to operate open-loop for distances exceeding
35 cm without failure, and can be controlled through teleoperation to navigate complex
paths.
}
comment = {
A revised version of this paper has appeared in the proceedings of the 12th International
Symposium of Robotics Research (ISRR 2005), San Francisco, CA, October 12th-15th,
2005.
}
}
@TechReport{Dartmouth:TR2005-563,
author = {Anne Loomis },
title = {{Computation reuse in stacking and unstacking}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-563},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/422/TR2005-563.pdf},
abstract = {
Algorithms for dynamic simulation and control are fundamental to many applications,
including computer games and movies, medical simulation, and mechanical design.
I propose to explore efficient algorithms for finding a stable unstacking sequence
-- an order in which we can remove every object from a structure without causing
the structure to collapse under gravity at any step.
We begin with a basic unstacking sequence algorithm: consider the set of all objects
in a structure. Collect all possible subsets into a disassembly graph. Search the
graph, testing the stability of each node as it is visited. Any path of stable nodes
from start to goal is a stable unstacking sequence.
I propose to show how we can improve the performance of individual stability tests
for three-dimensional structures with Coulomb friction, and give effective methods
for searching the disassembly graph. I will also analyze the computational complexity
of stable unstacking problems, and explore a classification of structures based
on characteristics of their stable unstacking sequences.
In preliminary work, I have shown that we can reuse computation from one stability
test of a planar subassembly to the next. The implementation, which solves the system
dynamics as a linear complementarity problem (LCP), outperforms an implementation
that solves the system statics as a linear program (LP). This is surprising because
LCPs are more complex than LPs, and dynamics equations are more complex than statics
equations.
}
comment = {
Master's thesis proposal.
}
}
@TechReport{Dartmouth:TR2005-561,
author = {Nikhil Bansal and Amit Chakrabarti and Amir Epstein and Baruch Schieber },
title = {{A Quasi-PTAS for Unsplittable Flow on Line Graphs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-561},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/421/TR2005-561.pdf},
abstract = {
We study the Unsplittable Flow Problem (UFP) on a line graph, focusing on the long-standing
open question of whether the problem is APX-hard. We describe a deterministic quasi-polynomial
time approximation scheme for UFP on line graphs, thereby ruling out an APX-hardness
result, unless NP is contained in DTIME(2^polylog(n)). Our result requires a quasi-polynomial
bound on all edge capacities and demands in the input instance. Earlier results
on this problem included a polynomial time (2+epsilon)-approximation under the assumption
that no demand exceeds any edge capacity (the "no-bottleneck assumption") and a
super-constant integrality gap if this assumption did not hold. Unlike most earlier
work on UFP, our results do not require a no-bottleneck assumption.
}
}
@TechReport{Dartmouth:TR2005-560,
author = {Amit Chakrabarti and Subhash Khot },
title = {{Combinatorial Theorems about Embedding Trees on the Real Line}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-560},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/420/TR2005-560.pdf},
abstract = {
We consider the combinatorial problem of embedding a tree metric into the real line
with low distortion. For two special families of trees --- the family of complete
binary trees and the family of subdivided stars --- we provide embeddings whose
distortion is provably optimal, up to a constant factor. We also prove that the
optimal distortion of a linear embedding of a tree can be arbitrarily low or high
even when it has bounded degree.
}
}
@TechReport{Dartmouth:TR2005-559,
author = {Meiyuan Zhao },
title = {{Performance Evaluation of Distributed Security Protocols Using Discrete Event Simulation}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-559},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/419/TR2005-559.pdf},
abstract = {
The Border Gateway Protocol (BGP) that manages inter-domain routing on the Internet
lacks security. Protective measures using public key cryptography introduce complexities
and costs.
To support authentication and other security functionality in large networks, we
need public key infrastructures (PKIs). Protocols that distribute and validate certificates
introduce additional complexities and costs. The certification path building algorithm
that helps users establish trust on certificates in the distributed network environment
is particularly complicated.
Neither routing security nor PKI come for free. Prior to this work, the research
study on performance issues of these large-scale distributed security systems was
minimal. In this thesis, we evaluate the performance of BGP security protocols and
PKI systems. We answer the questions about how the performance affects protocol
behaviors and how we can improve the efficiency of these distributed protocols to
bring them one step closer to reality.
The complexity of the Internet makes an analytical approach difficult; and the scale
of Internet makes empirical approaches also unworkable. Consequently, we take the
approach of simulation. We have built the simulation frameworks to model a number
of BGP security protocols and the PKI system. We have identified performance problems
of Secure BGP (S-BGP), a primary BGP security protocol, and proposed and evaluated
Signature Amortization (S-A) and Aggregated Path Authentication (APA) schemes that
significantly improve efficiency of S-BGP without compromising security. We have
also built a simulation framework for general PKI systems and evaluated certification
path building algorithms, a critical part of establishing trust in Internet-scale
PKI, and used this framework to improve algorithm performance.
}
comment = {
Ph.D. Thesis
}
}
@TechReport{Dartmouth:TR2005-558,
author = {Guanhua Yan },
title = {{Improving Large-Scale Network Traffic Simulation with Multi-Resolution Models}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-558},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/418/TR2005-558.pdf},
abstract = {
Simulating a large-scale network like the Internet is a challenging undertaking because
of the sheer volume of its traffic. Packet-oriented representation provides high-fidelity
details but is computationally expensive; fluid-oriented representation offers high
simulation efficiency at the price of losing packet-level details. Multi-resolution
modeling techniques exploit the advantages of both representations by integrating
them in the same simulation framework. This dissertation presents solutions to the
problems regarding the efficiency, accuracy, and scalability of the traffic simulation
models in this framework. The ``ripple effect'' is a well-known problem inherent
in event-driven fluid-oriented traffic simulation, causing explosion of fluid rate
changes. Integrating multi-resolution traffic representations requires estimating
arrival rates of packet-oriented traffic, calculating the queueing delay upon a
packet arrival, and computing packet loss rate under buffer overflow. Real time
simulation of a large or ultra-large network demands efficient background traffic
simulation. The dissertation includes a rate smoothing technique that provably mitigates
the ``ripple effect'', an accurate and efficient approach that integrates traffic
models at multiple abstraction levels, a sequential algorithm that achieves real
time simulation of the coarse-grained traffic in a network with 3 tier-1 ISP (Internet
Service Provider) backbones using an ordinary PC, and a highly scalable parallel
algorithm that simulates network traffic at coarse time scales.
}
comment = {
Ph.D dissertation. 183 pages. Advisor: David Nicol.
}
}
@TechReport{Dartmouth:TR2005-557,
author = {Siwei Lyu },
title = {{Natural Image Statistics for Digital Image Forensics}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-557},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/417/TR2005-557.pdf},
abstract = {
We describe a set of natural image statistics that are built upon two multi-scale
image decompositions, the quadrature mirror filter pyramid decomposition and the
local angular harmonic decomposition. These image statistics consist of first- and
higher-order statistics that capture certain statistical regularities of natural
images. We propose to apply these image statistics, together with classification
techniques, to three problems in digital image forensics: (1) differentiating photographic
images from computer-generated photorealistic images, (2) generic steganalysis;
(3) rebroadcast image detection. We also apply these image statistics to the traditional
art authentication for forgery detection and identification of artists in an art
work. For each application we show the effectiveness of these image statistics and
analyze their sensitivity and robustness.
}
comment = {
Ph.D dissertation. Advisor: Hany Farid.
}
}
@TechReport{Dartmouth:TR2005-556,
author = {Srdjan Petrovic },
title = {{Efficient Wait-Free Algorithms for Implementing LL/SC Objects}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-556},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/416/TR2005-556.pdf},
abstract = {
Over the past decade, a pair of instructions called load-linked (LL) and store-conditional
(SC) have emerged as the most suitable synchronization instructions for the design
of lock-free algorithms. However, current architectures do not support these instructions;
instead, they support either CAS (e.g., UltraSPARC, Itanium, Pentium) or restricted
versions of LL/SC (e.g., POWER4, MIPS, Alpha). Thus, there is a gap between what
algorithm designers want (namely, LL/SC) and what multiprocessors actually support
(namely, CAS or restricted LL/SC). To bridge this gap, this thesis presents a series
of efficient, wait-free algorithms that implement LL/SC from CAS or restricted LL/SC.
}
}
@TechReport{Dartmouth:TR2005-555,
author = {Valentino Crespi and George V. Cybenko and Guofei Jiang },
title = {{The Theory of Trackability with Applications to Sensor Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-555},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/415/TR2005-555.pdf},
abstract = {
In this paper, we formalize the concept of tracking in a sensor network and develop
a rigorous theory of {em trackability} that investigates the rate of growth of the
number of consistent tracks given a sequence of observations made by the sensor
network. The phenomenon being tracked is modelled by a nondeterministic finite automaton
and the sensor network is modelled by an observer capable of detecting events related,
typically ambiguously, to the states of the underlying automaton.
More formally, an input string, $Z^t$, of $t+1$ symbols (the sensor network observations)
that is presented to a nondeterministic finite automaton, $M$, (the model) determines
a set, ${cal H}_M(Z^t)$, of state sequences (the tracks or hypotheses) that are
capable of generating the input string $Z^t$. We study the growth of the size of
this set, $|{cal H}_M(Z^t)|$, as a function of the length of the input string, $t+1$.
Our main result is that for a given automaton and sensor coverage, the worst-case
rate of growth is either polynomial or exponential in $t$, indicating a kind of
phase transition in tracking accuracy.
The techniques we use include the Joint Spectral Radius, $rho(Sigma)$, of a finite
set, $Sigma$, of $(0,1)$-matrices derived from $M$. Specifically, we construct a
set of matrices, $Sigma$, corresponding to $M$ with the property that $rho(Sigma)
leq 1$ if and only if $|{cal H}_M(Z^t)|$ grows polynomially in $t$. We also prove
that for $(0,1)$-matrices, the decision problem $rho(Sigma)leq 1$ is Turing decidable
and, therefore, so is the problem of deciding whether worst case state sequence
growth for a given automaton is polynomial or exponential. These results have applications
in sensor networks, computer network security and autonomic computing as well as
various tracking problems of recent interest involving detecting phenomena using
noisy observations of hidden states.
}
}
@TechReport{Dartmouth:TR2005-554,
author = {Prasad Jayanti and Srdjan Petrovic },
title = {{Efficiently Implementing a Large Number of LL/SC Objects}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-554},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/414/TR2005-554.pdf},
abstract = {
Over the past decade, a pair of instructions called load-linked (LL) and store-conditional
(SC) have emerged as the most suitable synchronization instructions for the design
of lock-free algorithms. However, current architectures do not support these instructions;
instead, they support either CAS (e.g., UltraSPARC, Itanium) or restricted versions
of LL/SC (e.g., POWER4, MIPS, Alpha). Thus, there is a gap between what algorithm
designers want (namely, LL/SC) and what multiprocessors actually support (namely,
CAS or RLL/RSC). To bridge this gap, a flurry of algorithms that implement LL/SC
from CAS have appeared in the literature. The two most recent algorithms are due
to Doherty, Herlihy, Luchangco, and Moir (2004) and Michael (2004). To implement
M LL/SC objects shared by N processes, Doherty et al.'s algorithm uses only O(N
+ M) space, but is only non-blocking and not wait-free. Michael's algorithm, on
the other hand, is wait-free, but uses O(N^2 + M) space. The main drawback of his
algorithm is the time complexity of the SC operation: although the expected amortized
running time of SC is only O(1), the worst-case running time of SC is O(N^2). The
algorithm in this paper overcomes this drawback. Specifically, we design a wait-free
algorithm that achieves a space complexity of O(N^2 + M), while still maintaining
the O(1) worst-case running time for LL and SC operations.
}
}
@TechReport{Dartmouth:TR2005-553,
author = {Bruce R. Donald and Christopher G. Levey and Craig D. McGray and Igor Paprotny and Daniela Rus },
title = {{An Untethered, Electrostatic, Globally Controllable MEMS Micro-Robot: Supplementary videos}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-553},
year = {2005},
month = {January},
abstract = {
We present a steerable, electrostatic, untethered, MEMS micro-robot, with dimensions
of 60 µm by 250 µm by 10 µm. This micro-robot is
1 to 2 orders of magnitude smaller in size than previous micro-robotic systems.
The device consists of a curved, cantilevered steering arm, mounted on an untethered
scratch drive actuator. These two components are fabricated monolithically from
the same sheet of conductive polysilicon, and receive a common power and control
signal through a capacitive coupling with an underlying electrical grid. All locations
on the grid receive the same power and control signal, so that the devices can be
operated without knowledge of their position on the substrate and without constraining
rails or tethers. Control and power delivery waveforms are broadcast to the device
through the capacitive power coupling, and are decoded by the electromechanical
response of the device body. Individual control of the component actuators provides
two distinct motion gaits (forward motion and turning), which together allow full
coverage of a planar workspace (the robot is globally controllable). These MEMS
micro-robots demonstrate turning error of less than 3.7 °/mm during forward
motion, turn with radii as small as 176 µm, and achieve speeds of over
200 µm/sec, with an average step size of 12 nm. They have been shown
to operate open-loop for distances exceeding 35 cm without failure, and can
be controlled through teleoperation to navigate complex paths. This document contains
movies showing the actuation of the micro-robots during open-loop actuation and
teleoperation experiments. The videos have been sped up for ease of viewing. On
each video, the time-scale is noted in the lower-right corner of the screen.
}
comment = {
This technical report is a multimedia web page, available at
http://www.cs.dartmouth.edu/reports/TR2005-553.CD/index.html
}
}
@TechReport{Dartmouth:TR2005-552,
author = {Yougu Yuan },
title = {{On the Design of an Immersive Environment for Security-Related Studies}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-552},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/412/TR2005-552.pdf},
abstract = {
The Internet has become an essential part of normal operations of both public and
private sectors. Many security issues are not addressed in the original Internet
design, and security now has become a large concern for networking research and
study. There is an imperative need to have an simulation environment that can be
used to help study security-related research problems. In the thesis we present
our effort to build such an environment: Real-time Immersive Network Simulation
Environment (RINSE). RINSE features flexible configuration of models using various
networking protocols and real-time user interaction. We also present the Estimate
Next Infection (ENI) model we developed for Internet scanning worms using RINSE,
and the effort of combining multiple resolutions in worm modeling.
}
comment = {
Masters thesis. Advisor: David Nicol
}
}
@TechReport{Dartmouth:TR2005-551,
author = {Alexander Iliev and Sean Smith },
title = {{More Efficient Secure Function Evaluation Using Tiny Trusted Third Parties}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-551},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/411/TR2005-551.pdf},
abstract = {
We investigate the use of trustworthy devices, which function as trusted third parties
(TTPs), to solve general two-party Secure Function Evaluation (SFE) problems. We
assume that a really trustworthy TTP device will have very limited protected memory
and computation environment---a emph{tiny TTP}. This precludes trivial solutions
like "just run the function in the TTP".
Traditional scrambled circuit evaluation approaches to SFE have a very high overhead
in using indirectly-addressed arrays---every array access's cost is linear in the
array size. The main gain in our approach is that array access can be provided with
much smaller overhead---$O(sqrt{N}log N)$. This expands the horizon of problems
which can be efficiently solved using SFE. Additionally, our technique provides
a simple way to deploy arbitrary programs on tiny TTPs.
In our prototype, we use a larger (and expensive) device, the IBM 4758 secure coprocessor,
but we also speculate on the design of future tiny devices that could greatly improve
the current prototype's efficiency by being optimized for the operations prevalent
in our algorithms.
We have prototyped a compiler for the secure function definition language (SFDL)
developed in the Fairplay project. Our compiler produces an arithmetic circuit,
augmented with emph{array access gates} which provide more efficient secure access
to arrays. We then have a circuit interpreter in the 4758 to evaluate such a circuit
on given inputs. It does this gate by gate, requiring very little protected space.
We report on the performance of this prototype, which confirms our approach's strength
in handling indirectly-addressed arrays.
}
}
@TechReport{Dartmouth:TR2005-550,
author = {Guanling Chen and Heng Huang and Minkyong Kim },
title = {{Mining Frequent and Periodic Association Patterns}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-550},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/410/TR2005-550.pdf},
abstract = {
Profiling the clients' movement behaviors is useful for mobility modeling, anomaly
detection, and location prediction. In this paper, we study clients' frequent and
periodic movement patterns in a campus wireless network. We use offline data-mining
algorithms to discover patterns from clients' association history, and analyze the
reported patterns using statistical methods. Many of our results reflect the common
characteristics of a typical academic campus, though we also observed some unusual
association patterns. There are two challenges: one is to remove noise from data
for efficient pattern discovery, and the other is to interpret discovered patterns.
We address the first challenge using a heuristic-based approach applying domain
knowledge. The second issue is harder to address because we do not have the knowledge
of people's activities, but nonetheless we could make reasonable interpretation
of the common patterns.
}
}
@TechReport{Dartmouth:TR2005-549,
author = {Guanling Chen and David Kotz },
title = {{Structural Analysis of Social Networks with Wireless Users}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-549},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/409/TR2005-549.pdf},
abstract = {
Online interactions between computer users form Internet-based social networks. In
this paper we present a structural analysis of two such networks with wireless users.
In one network the wireless users participate in a global file-sharing system, and
in the other they interact with each other through a local music-streaming application.
}
}
@TechReport{Dartmouth:TR2005-548,
author = {Marco D. Adelfio },
title = {{Lower Bounds on the Communication Complexity of Shifting}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-548},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/408/TR2005-548.pdf},
abstract = {
We study the communication complexity of the SHIFT (equivalently, SUM-INDEX) function
in a 3-party simultaneous message model. Alice and Bob share an n-bit string x and
Alice holds an index i and Bob an index j. They must send messages to a referee
who knows only n, i and j, enabling him to determine x[(i+j) mod n]. Surprisingly,
it is possible to achieve nontrivial savings even with such a strong restriction:
Bob can now make do with only ceil(n/2) bits. Here we show that this bound is completely
tight, for all n. This is an exact lower bound, with no asymptotics involved.
}
comment = {
Senior Honors Thesis, 2005. Awarded High Honors.
}
}
@TechReport{Dartmouth:TR2005-547,
author = {Alexander Iliev and Sean Smith },
title = {{Towards Tiny Trusted Third Parties}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-547},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/407/TR2005-547.pdf},
abstract = {
Many security protocols hypothesize the existence of a {em trusted third party (TTP)}
to ease handling of computation and data too sensitive for the other parties involved.
Subsequent discussion usually dismisses these protocols as hypothetical or impractical,
under the assumption that trusted third parties cannot exist. However, the last
decade has seen the emergence of hardware-based devices that, to high assurance,
can carry out computation unmolested; emerging research promises more. In theory,
such devices can perform the role of a trusted third party in real-world problems.
In practice, we have found problems. The devices aspire to be general-purpose processors
but are too small to accommodate real-world problem sizes. The small size forces
programmers to hand-tune each algorithm anew, if possible, to fit inside the small
space without losing security. This tuning heavily uses operations that general-purpose
processors do not perform well. Furthermore, perhaps by trying to incorporate too
much functionality, current devices are also too expensive to deploy widely.
Our current research attempts to overcome these barriers, by focusing on the effective
use of {em tiny} TTPs ({em T3Ps}). To eliminate the programming obstacle, we used
our experience building hardware TTP apps to design and prototype an efficient way
to execute {em arbitrary} programs on T3Ps while preserving the critical trust properties.
To eliminate the performance and cost obstacles, we are currently examining the
potential hardware design for a T3P optimized for these operations.
In previous papers, we reported our work on the programming obstacle. In this paper,
we examine the potential hardware designs. We estimate that such a T3P could outperform
existing devices by several orders of magnitude, while also having a gate-count
of only 30K-60K, one to three orders of magnitude smaller than existing devices.
}
}
@TechReport{Dartmouth:TR2005-546,
author = {Robert Scot Drysdale and David P. Wagner },
title = {{Boolean operations with two dimensional segment trees}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-546},
year = {2005},
month = {January},
comment = {
Abstract and paper lost.
}
}
@TechReport{Dartmouth:TR2005-545,
author = {Siwei Lyu },
title = {{Automatic Image Orientation Determination with Natural Image Statistics}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-545},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/405/TR2005-545.pdf},
abstract = {
In this paper, we propose a new method for automatically determining image orientations.
This method is based on a set of natural image statistics collected from a multi-scale
multi-orientation image decomposition (e.g., wavelets). From these statistics, a
two-stage hierarchal classification with multiple binary SVM classifiers is employed
to de- termine image orientation. The proposed method is evaluated and compared
to existing methods with experiments performed on 18040 natural images, where it
showed promising performance.
}
}
@TechReport{Dartmouth:TR2005-544,
author = {Twum Djin },
title = {{Managing Access Control in Virtual Private Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-544},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/404/TR2005-544.pdf},
abstract = {
Virtual Private Network technology allows remote network users to benefit from resources
on a private network as if their host machines actually resided on the network.
However, each resource on a network may also have its own access control policies,
which may be completely unrelated to network access. Thus users access to a network
(even by VPN technology) does not guarantee their access to the sought resources.
With the introduction of more complicated access privileges, such as delegated access,
it is conceivable for a scenario to arise where a user can access a network remotely
(because of direct permissions from the network administrator or by delegated permission)
but cannot access any resources on the network. There is, therefore, a need for
a network access control mechanism that understands the privileges of each remote
network user on one hand, and the access control policies of various network resources
on the other hand, and so can aid a remote user in accessing these resources based
on the user's privileges.
This research presents a software solution in the form of a centralized access
control framework called an Access Control Service (ACS), that can grant remote
users network presence and simultaneously aid them in accessing various network
resources with varying access control policies. At the same time, the ACS provides
a centralized framework for administrators to manage access to their resources.
The ACS achieves these objectives using VPN technology, network address translation
and by proxying various authentication protocols on behalf of remote users.
}
comment = {
Senior honors thesis.
}
}
@TechReport{Dartmouth:TR2005-543,
author = {Robert A. Savell },
title = {{On-line Metasearch, Pooling, and System Evaluation}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-543},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/403/TR2005-543.pdf},
abstract = {
This thesis presents a unified method for simultaneous solution of three problems
in Information Retrieval--- metasearch (the fusion of ranked lists returned by retrieval
systems to elicit improved performance), efficient system evaluation (the accurate
evaluation of retrieval systems with small numbers of relevance judgements), and
pooling or ``active sample selection" (the selection of documents for manual judgement
in order to develop sample pools of high precision or pools suitable for assessing
system quality). The thesis establishes a unified theoretical framework for addressing
these three problems and naturally generalizes their solution to the on-line context
by incorporating feedback in the form of relevance judgements. The algorithm---
Rankhedge for on-line retrieval, metasearch and system evaluation--- is the first
to address these three problems simultaneously and also to generalize their solution
to the on-line context.
Optimality of the Rankhedge algorithm is developed via Bayesian and maximum entropy
interpretations. Results of the algorithm prove to be significantly superior to
previous methods when tested over a range of TREC (Text REtrieval Conference) data.
In the absence of feedback, the technique equals or exceeds the performance of benchmark
metasearch algorithms such as CombMNZ and Condorcet. The technique then dramatically
improves on this performance during the on-line metasearch process. In addition,
the technique generates pools of documents which include more relevant documents
and produce more accurate system evaluations than previous techniques. The thesis
includes an information-theoretic examination of the original Hedge algorithm as
well as its adaptation to the context of ranked lists. The work also addresses the
concept of information-theoretic similarity within the Rankhedge context and presents
a method for decorrelating the predictor set to improve worst case performance.
Finally, an information-theoretically optimal method for probabilistic ``active
sampling" is presented with possible application to a broad range of practical and
theoretical contexts.
}
comment = {
Doctoral dissertation. Advisors: Jay Aslam (NEU), Dan Rockmore, Chris Bailey-Kellogg,
and John Lafferty (CMU).
}
}
@TechReport{Dartmouth:TR2005-542,
author = {Matthew P. Bell },
title = {{A toy rock climbing robot}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-542},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/402/TR2005-542.pdf},
abstract = {
The goal of this thesis was to build a simple toy rock climbing robot, and to explore
problems related to grasping, path planning, and robot control. The robot is capable
of climbing a wall of pegs either under manual control through a host system and
an infrared interface, or on the basis of a set of pre-recorded keyframes. In addition,
the robot can climb certain peg configurations using a cyclic gait. The robot climbs
in an open-loop mode without sensor feedback. All communications are sent through
the IR connection, and the tether to the robot consists only of two power wires.
}
comment = {
Senior Honors Thesis. Advisor: Devin Balkcom.
}
}
@TechReport{Dartmouth:TR2005-541,
author = {Meiyuan Zhao and Sean W. Smith and David M. Nicol },
title = {{Aggregated Path Authentication for Efficient BGP Security}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-541},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/401/TR2005-541.pdf},
abstract = {
The border gateway protocol (BGP) controls inter-domain routing in the Internet.
BGP is vulnerable to many attacks, since routers rely on hearsay information from
neighbors. Secure BGP (S-BGP) uses DSA to provide route authentication and mitigate
many of these risks. However, many performance and deployment issues prevent S-BGP's
real-world deployment. Previous work has explored improving S-BGP processing latencies,
but space problems, such as increased message size and memory cost, remain the major
obstacles. In this paper, we combine two efficient cryptographic techniques---signature
amortization and aggregate signatures---to design new aggregated path authentication
schemes. We propose six constructions for aggregated path authentication that substantially
improve efficiency of S-BGP's path authentication on both speed and space criteria.
Our performance evaluation shows that the new schemes achieve such an efficiency
that they may overcome the space obstacles and provide a real-world practical solution
for BGP security.
}
}
@TechReport{Dartmouth:TR2005-540,
author = {Minkyong Kim and David Kotz },
title = {{Classifying the Mobility of Users and the Popularity of Access Points}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-540},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/400/TR2005-540.pdf},
abstract = {
There is increasing interest in location-aware systems and applications. It is important
for any designer of such systems and applications to understand the nature of user
and device mobility. Furthermore, an understanding of the effect of user mobility
on access points (APs) is also important for designing, deploying, and managing
wireless networks. Although various studies of wireless networks have provided insights
into different network environments and user groups, it is often hard to apply these
findings to other situations, or to derive useful abstract models.
In this paper, we present a general methodology for extracting mobility information
from wireless network traces, and for classifying mobile users and APs. We used
the Fourier transform to convert time-dependent location information to the frequency
domain, then chose the two strongest periods and used them as parameters to a classification
system based on Bayesian theory. To classify mobile users, we computed diameter
(the maximum distance between any two APs visited by a user during a fixed time
period) and observed how this quantity changes or repeats over time. We found that
user mobility had a strong period of one day, but there was also a large group of
users that had either a much smaller or much bigger primary period. Both primary
and secondary periods had important roles in determining classes of mobile users.
Users with one day as their primary period and a smaller secondary period were most
prevalent; we expect that they were mostly students taking regular classes. To classify
APs, we counted the number of users visited each AP. The primary period did not
play a critical role because it was equal to one day for most of the APs; the secondary
period was the determining parameter. APs with one day as their primary period and
one week as their secondary period were most prevalent. By plotting the classes
of APs on our campus map, we discovered that this periodic behavior of APs seemed
to be independent of their geographical locations, but may depend on the relative
locations of nearby APs. Ultimately, we hope that our study can help the design
of location-aware services by providing a base for user mobility models that reflect
the movements of real users.
}
comment = {
Revision of a paper that appeared at LoCA 2005.
}
}
@TechReport{Dartmouth:TR2005-539,
author = {Kwang-Hyun Baek and Sean W. Smith },
title = {{Preventing Theft of Quality of Service on Open Platforms}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-539},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/399/TR2005-539.pdf},
abstract = {
As multiple types of traffic converge onto one network (frequently wireless), enterprises
face a tradeoff between effectiveness and security. Some types of traffic, such
as voice-over-IP (VoIP), require certain quality of service (QoS) guarantees to
be effective. The end client platform is in the best position to know which packets
deserve this special handling. In many environments (such as universities), end
users relish having control over their own machines. However, if end users administer
their own machines, nothing stops dishonest ones from marking undeserving traffic
for high QoS. How can an enterprise ensure that only appropriate traffic receives
high QoS, while also allowing end users to retain control over their own machines?
In this paper, we present the design and prototype of a solution, using SELinux,
TCPA/TCG hardware, Diffserv, 802.1x, and EAP-TLS.
}
comment = {
REVISION 1 of May 5, 2005.
}
}
@TechReport{Dartmouth:TR2005-538,
author = {Robert Scot Drysdale and Clifford Stein and David P. Wagner },
title = {{An O(n^{5/2} log n) Algorithm for the Rectilinear Minimum Link-Distance Problem in Three Dimensions (Extended Abstract)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-538},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/398/TR2005-538.pdf},
abstract = {
In this paper we consider the Rectilinear Minimum Link-Distance Problem in Three
Dimensions. The problem is well studied in two dimensions, but is relatively unexplored
in higher dimensions. We solve the problem in O(B n log n) time, where n is the
number of corners among all obstacles, and B is the size of a BSP decomposition
of the space containing the obstacles. It has been shown that in the worst case
B = Theta(n^{3/2}), giving us an overall worst case time of O(n^{5/2} log n). Previously
known algorithms have had worst-case running times of Omega(n^3).
}
comment = {
Submitted to CCCG 2005
}
}
@TechReport{Dartmouth:TR2005-536,
author = {Vincent Berk and Annarita Giani and George Cybenko },
title = {{Detection of Covert Channel Encoding in Network Packet Delays}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-536},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/397/TR2005-536-rev1.pdf},
abstract = {
Covert channels are mechanisms for communicating information in ways that are difficult
to detect. Data exfiltration can be an indication that a computer has been compromised
by an attacker even when other intrusion detection schemes have failed to detect
a successful attack. Covert timing channels use packet inter-arrival times, not
header or payload embedded information, to encode covert messages. This paper investigates
the channel capacity of Internet-based timing channels and proposes a methodology
for detecting covert timing channels based on how close a source comes to achieving
that channel capacity. A statistical approach is then used for the special case
of binary codes.
}
comment = {
This revision differs from the original only in the correction of one reference.
}
}
@TechReport{Dartmouth:TR2005-535,
author = {John Thomas and Naren Ramakrishnan and Chris Bailey-Kellogg },
title = {{Graphical Models of Residue Coupling in Protein Families}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-535},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/396/TR2005-535.pdf},
abstract = {
Identifying residue coupling relationships within a protein family can provide important
insights into intrinsic molecular processes, and has significant applications in
modeling structure and dynamics, understanding function, and designing new or modified
proteins. We present the first algorithm to infer an undirected graphical model
representing residue coupling in protein families. Such a model serves as a compact
description of the joint amino acid distribution, and can be used for predictive
(will this newly designed protein be folded and functional?), diagnostic (why is
this protein not stable or functional?), and abductive reasoning (what if I attempt
to graft features of one protein family onto another?). Unlike current correlated
mutation algorithms that are focused on assessing dependence, which can conflate
direct and indirect relationships, our algorithm focuses on assessing independence,
which modularizes variation and thus enables efficient reasoning of the types described
above. Further, our algorithm can readily incorporate, as priors, hypotheses regarding
possible underlying mechanistic/energetic explanations for coupling. The resulting
approach constitutes a powerful and discriminatory mechanism to identify residue
coupling from protein sequences and structures. Analysis results on the G-protein
coupled receptor (GPCR) and PDZ domain families demonstrate the ability of our approach
to effectively uncover and exploit models of residue coupling.
}
comment = {
To appear in BIOKDD05.
}
}
@TechReport{Dartmouth:TR2005-534,
author = {David Kotz },
title = {{Department of Computer Science Activity 1998-2004}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-534},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/395/TR2005-534.pdf},
abstract = {
This report summarizes much of the research and teaching activity of the Department
of Computer Science at Dartmouth College between late 1998 and late 2004. The material
for this report was collected as part of the final report for NSF Institutional
Infrastructure award EIA-9802068, which funded equipment and technical staff during
that six-year period. This equipment and staff supported essentially all of the
departments research activity during that period.
}
}
@TechReport{Dartmouth:TR2005-533,
author = {Soumendra Nanda },
title = {{Spatial Multipath Location Aided Routing}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-533},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/394/TR2005-533.pdf},
abstract = {
Mobile ad-hoc networks (MANETs) are infrastructure-free networks of mobile nodes
that communicate with each other wirelessly. There are several routing schemes that
have been proposed and several of these have been already extensively simulated
or implemented as well. The primary applications of such networks have been in disaster
relief operations, military use, conferencing and environment sensing. There are
several ad hoc routing algorithms at present that utilize position information (usually
in two dimensional terms) to make routing decisions at each node. Our goal is to
utilize three-dimensional (3D) position information to provide more reliable as
well as efficient routing for certain applications. We thus describe extensions
to various location aware routing algorithms to work in 3D. We propose a new hierarchical,
zone-based 3D routing algorithm, based on GRID by Liao, Tseng and Sheu. Our new
algorithm called "Hyper-GRID" is a hybrid algorithm that uses multipath routing
(alternate path caching) in 3D. We propose replacing LAR with Multipath LAR (MLAR)
in GRID. We have implemented MLAR and are validating MLAR through simulation using
ns-2 and studying its efficiency, scalability and other properties. We use a random
waypoint mobility model and compare our MLAR approach versus LAR, AODV and AOMDV
in both 2D and 3D for a range of traffic and mobility scenarios. Our simulation
results demonstrate the performance benefits of MLAR over LAR and AODV in most mobility
situations. AOMDV delivers more packets than MLAR consistently, but does so at the
cost of more frequent flooding of control packets and thus higher bandwidth usage
than MLAR.
}
comment = {
MS Thesis ,Originally submitted 6th June 2004, Advised by Robert S. Gray
}
}
@TechReport{Dartmouth:TR2005-532,
author = {John Marchesini and Sean Smith },
title = {{SHEMP: Secure Hardware Enhanced MyProxy}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-532},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/393/TR2005-532.pdf},
abstract = {
While PKI applications differ in how they use keys, all applications share one assumption:
users have keypairs. In previous work, we established that desktop keystores are
not safe places to store private keys, because the TCB is too large. These keystores
are also immobile, difficult to use, and make it impossible for relying parties
to make reasonable trust judgments. Since we would like to use desktops as PKI clients
and cannot realistically expect to redesign the entire desktop, this paper presents
a system that works within the confines of modern desktops to shrink the TCB needed
for PKI applications. Our system (called Secure Hardware Enhanced MyProxy (SHEMP))
shrinks the TCB in space and allows the TCB's size to vary over time and over various
application sensitivity levels, thus making desktops usable for PKI.
}
}
@TechReport{Dartmouth:TR2005-531,
author = {Alin C. Popescu },
title = {{Statistical Tools for Digital Image Forensics}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-531},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/392/TR2005-531.pdf},
abstract = {
A digitally altered image, often leaving no visual clues of having been tampered
with, can be indistinguishable from an authentic image. The tampering, however,
may disturb some underlying statistical properties of the image. Under this assumption,
we propose five techniques that quantify and detect statistical perturbations found
in different forms of tampered images: (1) re-sampled images (e.g., scaled or rotated);
(2) manipulated color filter array interpolated images; (3) double JPEG compressed
images; (4) images with duplicated regions; and (5) images with inconsistent noise
patterns. These techniques work in the absence of any embedded watermarks or signatures.
For each technique we develop the theoretical foundation, show its effectiveness
on credible forgeries, and analyze its sensitivity and robustness to simple counter-attacks.
}
comment = {
Ph.D. thesis, advisor: Hany Farid.
}
}
@TechReport{Dartmouth:TR2005-530,
author = {Ramgopal R. Mettu and Ryan H. Lilien and Bruce R. Donald },
title = {{High-Throughput Inference of Protein-Protein Interaction Sites from Unassigned NMR Data by Analyzing Arrangements Induced By Quadratic Forms on 3-Manifolds}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2005-530},
year = {2005},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/391/TR2005-530.pdf},
abstract = {
We cast the problem of identifying protein-protein interfaces, using only unassigned
NMR spectra, into a geometric clustering problem. Identifying protein-protein interfaces
is critical to understanding inter- and intra-cellular communication, and NMR allows
the study of protein interaction in solution. However it is often the case that
NMR studies of a protein complex are very time-consuming, mainly due to the bottleneck
in assigning the chemical shifts, even if the apo structures of the constituent
proteins are known. We study whether it is possible, in a high-throughput manner,
to identify the interface region of a protein complex using only unassigned chemical
shift and residual dipolar coupling (RDC) data. We introduce a geometric optimization
problem where we must cluster the cells in an arrangement on the boundary of a 3-manifold.
The arrangement is induced by a spherical quadratic form, which in turn is parameterized
by SO(3)xR^2. We show that this formalism derives directly from the physics of RDCs.
We present an optimal algorithm for this problem that runs in O(n^3 log n) time
for an n-residue protein. We then use this clustering algorithm as a subroutine
in a practical algorithm for identifying the interface region of a protein complex
from unassigned NMR data. We present the results of our algorithm on NMR data for
7 proteins from 5 protein complexes and show that our approach is useful for high-throughput
applications in which we seek to rapidly identify the interface region of a protein
complex.
}
comment = {
A revised version of this paper has been accepted for publication and will appear
at ISMB (2005) and Bioinformatics (2005).
}
}
@TechReport{Dartmouth:TR2004-529,
author = {Kazuhiro Minami and David Kotz },
title = {{Secure Context-sensitive Authorization}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-529},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/390/TR2004-529.pdf},
abstract = {
There is a recent trend toward rule-based authorization systems to achieve flexible
security policies. Also, new sensing technologies in pervasive computing make it
possible to define context-sensitive rules, such as ``allow database access only
to staff who are currently located in the main office.'' However, these rules, or
the facts that are needed to verify authority, often involve sensitive context information.
This paper presents a secure context-sensitive authorization system that protects
confidential information in facts or rules. Furthermore, our system allows multiple
hosts in a distributed environment to perform the evaluation of an authorization
query in a collaborative way; we do not need a universally trusted central host
that maintains all the context information. The core of our approach is to decompose
a proof for making an authorization decision into a set of sub-proofs produced on
multiple different hosts, while preserving the integrity and confidentiality policies
of the mutually untrusted principals operating these hosts. We prove the correctness
of our algorithm.
}
}
@TechReport{Dartmouth:TR2004-528,
author = {Hany Farid },
title = {{Discrete-Time Fractional Differentiation from Integer Derivatives}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-528},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/389/TR2004-528.pdf},
abstract = {
Discrete-time fractional derivative filters (1-D and 2-D) are shown to be well approximated
from a small set of integer derivatives. A fractional derivative of arbitrary order
(and, in 2-D, of arbitrary orientation) can therefore be efficiently computed from
a linear combination of integer derivatives of the underlying signal or image.
}
}
@TechReport{Dartmouth:TR2004-526,
author = {Lea Wittie },
title = {{Type-Safe Operating System Abstractions}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-526},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/388/TR2004-526.pdf},
abstract = {
Operating systems and low-level applications are usually written in languages like
C and assembly, which provide access to low-level abstractions. These languages
have unsafe type systems that allow many bugs to slip by programmers. For example,
in 1988, the Internet Worm exploited several insecure points in Unix including the
finger command. A call to finger with an unexpected argument caused a buffer overflow,
leading to the shutdown of most Internet traffic. A finger application written in
a type-safe language would have prevented its exploit and limited the points the
Internet Worm could attack. Such vulnerabilities are unacceptable in security-critical
applications such as the secure coprocessors of the Marianas network, secStore key
storage from Plan 9, and self-securing storage.
This research focuses on safe language techniques for building OS components that
cannot cause memory or IO errors. For example, an Ethernet device driver communicates
with its device through IO operations. The device depends on FIFO queues to send
and receive packets. A mistake in an IO operation can overflow or underflow the
FIFO queues, cause memory errors, or cause configuration inconsistencies on the
device. Data structures such as FIFO queues can be written safely in safe languages
such as Java and ML but these languages do not allow the access to the low-level
resources that an OS programmer needs. Therefore, safe OS components require a language
that combines the safety of Java with the low-level control of C.
My research formalizes the concurrency, locks, and system state needed by the safety-critical
areas of a device driver. These formal concepts are built on top of an abstract
syntax and rules that guarantees basic memory safety using linear and singleton
types to implement safe memory load and store operations. I proved that the improved
abstract machine retains the property of soundness, which means that all well-typed
programs will be able to execute until they reach an approved end-state. Together,
the concurrency, locks, and state provide safety for IO operations and data structures.
Using the OSKit from the University of Utah as a starting point, I developed a
small operating system. I ported the 3c509 Ethernet device driver from C to Clay,
a C-like type-safe language that uses a type system powerful enough to enforce invariants
about low-level devices and data structures. The resulting driver works safely in
a multi-threaded environment. It is guaranteed to obtain locks before using shared
data. It cannot cause a FIFO queue to overflow or underflow and it will only call
IO operations when invariants are satisfied.
This type-safe driver demonstrates an actual working application of the theoretical
components of my research. The abstract machine is powerful enough to encode a given
OS specification and enforce a provably matching implementation. These results lead
towards fundamentally secure computing environments.
}
comment = {
Doctoral dissertation. Advisor: Chris Hawblitzel
}
}
@TechReport{Dartmouth:TR2004-525,
author = {John Marchesini and Sean W. Smith },
title = {{Secure Hardware Enhanced MyProxy}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-525},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/387/TR2004-525.pdf},
abstract = {
In 1976, Whitfield Diffie and Martin Hellman demonstrated how "New Directions In
Cryptography" could enable secure information exchange between parties that do not
share secrets. In order for public key cryptography to work in modern distributed
environments, we need an infrastructure for finding and trusting other parties'
public keys (i.e., a PKI). A number of useful applications become possible with
PKI. While the applications differ in how they use keys (e.g., S/MIME uses the key
for message encryption and signing, while client-side SSL uses the key for authentication),
all applications share one assumption: users have keypairs.
In previous work, we examined the security aspects of some of the standard keystores
and the their interaction with the OS. We concluded that desktops are not safe places
to store private keys, and we demonstrated the permeability of keystores such as
the default Microsoft keystore and the Mozilla keystore. In addition to being unsafe,
these desktop keystores have the added disadvantage of being immobile.
In other previous work, we examined trusted computing. In industry, a new trusted
computing initiative has emerged: the Trusted Computing Platform Alliance (TCPA)
(now renamed the Trusted Computing Group (TCG)). The goal of the TCG design is lower-assurance
security that protects an entire desktop platform and is cheap enough to be commercially
feasible. Last year, we built a trusted computing platform based on the TCG specifications
and hardware.
The picture painted by these previous projects suggests that common desktops are
not secure enough for use as PKI clients, and trusted computing can improve the
security of client machines. The question that I propose to investigate is: "Can
I build a system which applies trusted computing hardware in a reasonable manner
in order to make desktops usable for PKI?" My design begins with the Grid community's
"MyProxy" credential repository, and enhances it to take advantage of secure hardware
on the clients, at the repository, and in the policy framework. The result is called
"Secure Hardware Enhanced MyProxy".
}
}
@TechReport{Dartmouth:TR2004-524,
author = {Kwang-Hyun Baek and Sean W. Smith and David Kotz },
title = {{A Survey of WPA and 802.11i RSN Authentication Protocols}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-524},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/386/TR2004-524.pdf},
abstract = {
In the new standards for WLAN security, many choices exist for the authentication
process. In this paper, we list eight desired properties of WLAN authentication
protocols, survey eight recent authentication protocols, and analyze the protocols
according to the desired properties.
}
}
@TechReport{Dartmouth:TR2004-523,
author = {Prasad Jayanti and Srdjan Petrovic },
title = {{Efficient Wait-Free Implementation of Multiword LL/SC Variables}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-523},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/385/TR2004-523.pdf},
abstract = {
Since the design of lock-free data structures often poses a formidable intellectual
challenge, researchers are constantly in search of abstractions and primitives that
simplify this design. The multiword LL/SC object is such a primitive: many existing
algorithms are based on this primitive, including the nonblocking and wait-free
universal constructions of Anderson and Moir (1995), the closed objects construction
of Chandra et al.(1998) and the snapshot algorithms of Jayanti (2002, 2004).
In this paper, we consider the problem of implementing a W-word LL/SC object shared
by N processes. The previous best algorithm, due to Anderson and Moir (1995), is
time optimal (LL and SC operations run in O(W) time), but has a space complexity
of O(N^2W). We present an algorithm that uses novel buffer management ideas to cut
down the space complexity by a factor of N to O(NW), while still being time optimal.
}
}
@TechReport{Dartmouth:TR2004-521,
author = {Chris Hawblitzel and Heng Huang and Lea Wittie },
title = {{Composing a Well-Typed Region}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-521},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/384/TR2004-521.pdf},
abstract = {
Efficient low-level systems need more control over memory than safe high-level languages
usually provide. In particular, safe languages usually prohibit explicit deallocation,
in order to prevent dangling pointers. Regions provide one safe deallocation mechanism;
indeed, many region calculi have appeared recently, each with its own set of operations
and often complex rules. This paper encodes regions from lower-level typed primitives
(linear memory, coercions, and delayed types), so that programmers can design their
own region operations and rules.
}
}
@TechReport{Dartmouth:TR2004-520,
author = {Siwei Lyu },
title = {{Mercer Kernels for Object Recognition with Local Features}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-520},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/383/TR2004-520.pdf},
abstract = {
In this paper, we propose a new class of kernels for object recognition based on
local image feature representations. Formal proofs are given to show that these
kernels satisfy the Mercer condition and reflect similarities between sets of local
features. In addition, multiple types of local features and semilocal constraints
are incorporated to reduce mismatches between local features, thus further improve
the classification performance. Experimental results of SVM classifiers coupled
with the proposed kernels are reported on ecognition tasks with the standard COIL-100
database and compared with existing methods. The proposed kernels achieved satisfactory
performance and were robust to changes in object configurations and image degradations.
}
comment = {
Submitted to CVPR 2005.
}
}
@TechReport{Dartmouth:TR2004-519,
author = {Robert C. Fitch },
title = {{Heterogeneous Self-Reconfiguring Robotics}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-519},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/382/TR2004-519.pdf},
abstract = {
Self-reconfiguring (SR) robots are modular systems that can autonomously change shape,
or reconfigure, for increased versatility and adaptability in unknown environments.
In this thesis, we investigate planning and control for systems of non-identical
modules, known as heterogeneous SR robots. Although previous approaches rely on
module homogeneity as a critical property, we show that the planning complexity
of fundamental algorithmic problems in the heterogeneous case is equivalent to that
of systems with identical modules. Primarily, we study the problem of how to plan
shape changes while considering the placement of specific modules within the structure.
We characterize this key challenge in terms of the amount of free space available
to the robot and develop a series of decentralized reconfiguration planning algorithms
that assume progressively more severe free space constraints and support reconfiguration
among obstacles. In addition, we compose our basic planning techniques in different
ways to address problems in the related task domains of positioning modules according
to function, locomotion among obstacles, self-repair, and recognizing the achievement
of distributed goal-states. We also describe the design of a novel simulation environment,
implementation results using this simulator, and experimental results in hardware
using a planar SR system called the Crystal Robot. These results encourage development
of heterogeneous systems. Our algorithms enhance the versatility and adaptability
of SR robots by enabling them to use functionally specialized components to match
capability, in addition to shape, to the task at hand.
}
comment = {
Doctoral dissertation. Advisor: Daniela Rus
}
}
@TechReport{Dartmouth:TR2004-518,
author = {Hany Farid },
title = {{Creating and Detecting Doctored and Virtual Images: Implications to The Child Pornography Prevention Act}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-518},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/381/TR2004-518.pdf},
abstract = {
The 1996 Child Pornography Prevention Act (CPPA) extended the existing federal criminal
laws against child pornography to include certain types of "virtual porn". In 2002,
the United States Supreme Court found that portions of the CPPA, being overly broad
and restrictive, violated First Amendment rights. The Court ruled that images containing
an actual minor or portions of a minor are not protected, while computer generated
images depicting a fictitious "computer generated" minor are constitutionally protected.
In this report I outline various forms of digital tampering, placing them in the
context of this recent ruling. I also review computational techniques for detecting
doctored and virtual (computer generated) images.
}
}
@TechReport{Dartmouth:TR2004-517,
author = {Geeta Chaudhry },
title = {{Parallel Out-of-Core Sorting: The Third Way}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-517},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/380/TR2004-517.pdf},
abstract = {
Sorting very large datasets is a key subroutine in almost any application that is
built on top of a large database. Two ways to sort out-of-core data dominate the
literature: merging-based algorithms and partitioning-based algorithms. Within these
two paradigms, all the programs that sort out-of-core data on a cluster rely on
assumptions about the input distribution.
We propose a third way of out-of-core sorting: oblivious algorithms. In all, we
have developed six programs that sort out-of-core data on a cluster. The first three
programs, based completely on Leighton's columnsort algorithm, have a restriction
on the maximum problem size that they can sort. The other three programs relax this
restriction; two are based on our original algorithmic extensions to columnsort.
We present experimental results to show that our algorithms perform well. To the
best of our knowledge, the programs presented in this thesis are the first to sort
out-of-core data on a cluster without making any simplifying assumptions about the
distribution of the data to be sorted.
}
comment = {
Doctoral dissertation. Advisor: Thomas H. Cormen
}
}
@TechReport{Dartmouth:TR2004-515,
author = {Alin C. Popescu and Hany Farid },
title = {{Exposing Digital Forgeries by Detecting Duplicated Image Regions}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-515},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/379/TR2004-515.pdf},
abstract = {
We describe an efficient technique that automatically detects duplicated regions
in a digital image. This technique works by first applying a principal component
analysis to small fixed-size image blocks to yield a reduced dimension representation.
This representation is robust to minor variations in the image due to additive noise
or lossy compression. Duplicated regions are then detected by lexicographically
sorting all of the image blocks. We show the efficacy of this technique on credible
forgeries, and quantify its robustness and sensitivity to additive noise and lossy
JPEG compression.
}
}
@TechReport{Dartmouth:TR2004-514,
author = {Guanling Chen },
title = {{Solar: Building A Context Fusion Network for Pervasive Computing}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-514},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/378/TR2004-514.pdf},
abstract = {
The complexity of developing context-aware pervasive-computing applications calls
for distributed software infrastructures that assist applications to collect, aggregate,
and disseminate contextual data. In this dissertation, we present a Context Fusion
Network (CFN), called Solar, which is built with a scalable and self-organized service
overlay. Solar is flexible and allows applications to select distributed data sources
and compose them with customized data-fusion operators into a directed acyclic information
flow graph. Such a graph represents how an application computes high-level understandings
of its execution context from low-level sensory data. To manage application-specified
operators on a set of overlay nodes called Planets, Solar provides several unique
services such as application-level multicast with policy-driven data reduction to
handle buffer overflow, context-sensitive resource discovery to handle environment
dynamics, and proactive monitoring and recovery to handle common failures. Experimental
results show that these services perform well on a typical DHT-based peer-to-peer
routing substrate. In this dissertation, we also discuss experience, insights, and
lessons learned from our quantitative analysis of the input sensors, a detailed
case study of a Solar application, and development of other applications in different
domains.
}
comment = {
This is a reformatted version of Guanling Chen's Ph.D. dissertation. Unlike the dissertation
submitted to Dartmouth College, this version is single-spaced, uses 11pt fonts,
and is formatted specifically for double-sided printing.
}
}
@TechReport{Dartmouth:TR2004-513,
author = {Jue Wang },
title = {{Performance Evaluation of a Resource Discovery Service}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-513},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/377/TR2004-513.pdf},
abstract = {
In a pervasive computing environment, the number and variety of resources (services,
devices, and contextual information resources) make it necessary for applications
to accurately discover the best ones quickly. Thus a resource-discovery service,
which locates specific resources and establishes network connections as better resources
become available, is necessary for those applications. The performance of the resource-discovery
service is important when the applications are in a dynamic and mobile environment.
In this thesis, however, we do not focus on the resource- discovery technology itself,
but the evaluation of the scalability and mobility of the resource discovery module
in Solar, a context fusion middleware. Solar has a naming service that provides
resource discovery, since the resource names encode static and dynamic attributes.
The results of our experiments show that Solar's resource discovery performed generally
well in a typical dynamic environment, although Solar can not be scaled as well
as it should. And we identify the implementation issues related to that problem.
We also discuss experience, insights, and lessons learned from our quantitative
analysis of the experiment results.
}
}
@TechReport{Dartmouth:TR2004-512,
author = {Kimberly S. Powell },
title = {{Testing the Greenpass Wireless Security System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-512},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/376/TR2004-512.pdf},
abstract = {
Greenpass, developed by Nick Goffee, Sung Hoon Kim, Meiyuan Zhao and John Marchesini
under the supervision of Sean Smith and Punch Taylor, is a wireless security solution
that implements SPKI/SDSI delegation on top of X.509 keypairs within the EAP-TLS
authentication protocol. This system aims to model the decentralized way that authorization
flows in real-world enterprise settings and provide a seamless solution that allows
for easy access to all resources in the network by both registered users and authorized
guests. These goals are achieved through the deployment of a delegation tool, which
allows an active entity associated to the organization's network to grant authorization
to another entity previously unauthorized to use the network.
This paper describes the testing process of the first prototype for this system.
It examines trust and usability issues of the Greenpass Wireless Security System
and determines the accuracy of the system's implementation in relation to its objectives.
It then addresses the planning and execution of a small-scale demo for this prototype
based on the examined issues and makes projections for further tests on a larger
scale.
}
comment = {
Senior Honors Thesis. Advisors: Sean Smith and Denise Anthony
}
}
@TechReport{Dartmouth:TR2004-511,
author = {Robert S. Gray and David Kotz and Calvin Newport and Nikita Dubrovsky and Aaron Fiske and Jason Liu and Christopher Masone and Susan McGrath and Yougu Yuan },
title = {{Outdoor Experimental Comparison of Four Ad Hoc Routing Algorithms}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-511},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/375/TR2004-511.pdf},
abstract = {
Most comparisons of wireless ad hoc routing algorithms involve simulated or indoor
trial runs, or outdoor runs with only a small number of nodes, potentially leading
to an incorrect picture of algorithm performance. In this paper, we report on the
results of an outdoor trial run of four different routing algorithms, APRL, AODV,
GPSR, and STARA, running on top of thirty-three 802.11-enabled laptops moving randomly
through an athletic field. The laptops generated random traffic according to the
traffic patterns observed in a prototype application, and ran each routing algorithm
for a fifteen-minute period over the course of the hour-long trial run. The 33-laptop
experiment represents one of the largest outdoor tests of wireless routing algorithms,
and three of the algorithms each come from a different algorithmic class, providing
insight into the behavior of ad hoc routing algorithms at larger real-world scales
than have been considered so far. In addition, we compare the outdoor results with
both indoor ("tabletop") and simulation results for the same algorithms, examining
the differences between the indoor results and the outdoor reality. The paper also
describes the software infrastructure that allowed us to implement the ad hoc routing
algorithms in a comparable way, and use the same codebase for indoor, outdoor, and
simulated trial runs.
}
comment = {
See also TR2004-507 and TR2004-504.
}
}
@TechReport{Dartmouth:TR2004-510,
author = {Sung Hoon Kim },
title = {{Greenpass RADIUS Tools for Delegated Authorization in Wireless Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-510},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/374/TR2004-510.pdf},
abstract = {
Dartmouth's Greenpass project extends how public key cryptography can be used to
secure the wireless LAN with a RADIUS (Remote Authentication Dial In User Service)
server that is responsible for handling authentication requests from clients (called
supplicants in the 802.1x authentication model). This thesis describes the design
and implementation of the authentication process of Greenpass, specifically what
decisions are made in determining who is granted access and how a small modification
of already existing protocols can be used to provide guest access in a way that
better reflects how delegation of authority works in the real world.
Greenpass takes advantage of the existing PKI to authenticate local Dartmouth users
via X.509 identity certificates using EAP-TLS. We use the flexibility of SPKI/SDSI
(Simple Public Key Infrastructure/Simple Distributed Security Infrastructure) authorization
certificates to distribute the responsibility of delegating access to guests to
certain authorized delegators, avoiding some of the necessary steps and paperwork
associated with having a large centralized entity responsible for the entire institution.
This thesis also discusses how our solution can be adapted to support different
methods of guest delegation and investigates the possibility of eliminating the
cumbersome central entity and administrative overhead traditionally associated with
public key cryptography.
}
comment = {
Masters thesis. Advisor: Sean Smith
}
}
@TechReport{Dartmouth:TR2004-509,
author = {Nicholas C. Goffee },
title = {{Greenpass Client Tools for Delegated Authorization in Wireless Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-509},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/373/TR2004-509.pdf},
abstract = {
Dartmouth's Greenpass project seeks to provide strong access control to a wireless
network while simultaneously providing flexible guest access; to do so, it augments
the Wi-Fi Alliance's existing WPA standard, which offers sufficiently strong user
authentication and access control, with authorization based on SPKI certificates.
SPKI allows certain local users to delegate network access to guests by issuing
certificates that state, in essence, "he should get access because I said it's okay."
The Greenpass RADIUS server described in Kim's thesis [55] performs an authorization
check based on such statements so that guests can obtain network access without
requiring a busy network administrator to set up new accounts in a centralized database.
To our knowledge, Greenpass is the first working delegation-based solution to Wi-Fi
access control.
My thesis describes the Greenpass client tools, which allow a guest to introduce
himself to a delegator and allow the delegator to issue a new SPKI certificate to
the guest. The guest does not need custom client software to introduce himself or
to connect to the Wi-Fi network. The guest and delegator communicate using a set
of Web applications. The guest obtains a temporary key pair and X.509 certificate
if needed, then sends his public key value to a Web server we provide. The delegator
looks up her guest's public key and runs a Java applet that lets her verify her
guests' identity using visual hashing and issue a new SPKI certificate to him. The
guest's new certificate chain is stored as an HTTP cookie to enable him to "push"
it to an authorization server at a later time. I also describe how Greenpass can
be extended to control access to a virtual private network (VPN) and suggest several
interesting future research and development directions that could build on this
work.
}
comment = {
Masters thesis. Advisor: Sean Smith
}
}
@TechReport{Dartmouth:TR2004-508,
author = {Eric G. Krupski },
title = {{PPL: a Packet Processing Language}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-508},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/372/TR2004-508.pdf},
abstract = {
Any computing device or system that uses the internet needs to analyze and identify
the contents of network packets. Code that does this is often written in C, but
reading, identifying, and manipulating network packets in C requires writing tricky
and tedious code. Previous work has offered specification languages for describing
the format of network packets, which would allow packet type identification without
the hassles of doing this task in C. For example, McCann and Chandra's Packet Types
[3] system allows the programmer to define arbitrary packet types and generates
C unctions which match given data against a specified packet type. This paper will
present a packet processing language named PPL, which extends McCann and Chandras
Packet Types to allow the programmer to not only describe arbitrary packet types,
but also to control when and how a matching is attempted, with ML-style pattern
matching. PPL is intended for multiple applications, such as intrusion detection
systems, quick prototypes of new protocols, and IP de-multiplexing code.
}
comment = {
Senior Honors Thesis. Advisor: Chris Hawblitzel. Code and other materials available
at http://www.cs.dartmouth.edu/reports/TR2004-508.tgz (440KB).
}
}
@TechReport{Dartmouth:TR2004-507,
author = {David Kotz and Calvin Newport and Robert S. Gray and Jason Liu and Yougu Yuan and Chip Elliott },
title = {{Experimental evaluation of wireless simulation assumptions}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-507},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/371/TR2004-507.pdf},
abstract = {
All analytical and simulation research on ad~hoc wireless networks must necessarily
model radio propagation using simplifying assumptions. Although it is tempting to
assume that all radios have circular range, have perfect coverage in that range,
and travel on a two-dimensional plane, most researchers are increasingly aware of
the need to represent more realistic features, including hills, obstacles, link
asymmetries, and unpredictable fading. Although many have noted the complexity of
real radio propagation, and some have quantified the effect of overly simple assumptions
on the simulation of ad~hoc network protocols, we provide a comprehensive review
of six assumptions that are still part of many ad~hoc network simulation studies.
In particular, we use an extensive set of measurements from a large outdoor routing
experiment to demonstrate the weakness of these assumptions, and show how these
assumptions cause simulation results to differ significantly from experimental results.
We close with a series of recommendations for researchers, whether they develop
protocols, analytic models, or simulators for ad~hoc wireless networks.
}
comment = {
This paper is significantly revised and extended from TR2003-467, "The mistaken axioms
of wireless-network research."
}
}
@TechReport{Dartmouth:TR2004-506,
author = {Paul J. Mazzuca },
title = {{Access Control in a Distributed Decentralized Network: An XML Approach to Network Security using XACML and SAML}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-506},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/370/TR2004-506.pdf},
abstract = {
The development of eXtensible Distributed Access Control (XDAC) systems is influenced
by the transference of data access and storage from the local computer to the network.
In this distributed system, access control is determined by independent components
which transmit requests and decisions over a network, utilizing XML signing capabilities
found in the Security Assertion Markup Language (SAML). All resources in the XDAC
system are protected by the first component, a Policy Enforcement Point (PEP), which
acts as the main divider between the requesting entity and the requested resource.
The PEP grants access to a resource only if the second component, a Policy Decision
Point (PDP), returns a permit response after consulting a set of applicable policies
based on the requester's attributes, the resource, the action that the requester
desires to apply to that resource, and optionally the environment.
With Sun's eXtensible Access Control Markup Language (XACML), the XML encoded policies
can be combined among multiple nodes across a network using XACML rules and algorithms
to formulate a single decision based on an XACML request. In this thesis project,
I build a secure and efficient XDAC System based on XACML, implement an extension
to the SAML Assertion design by including XACML Attributes and Results, describe
in-detail about the many features that a XDAC System should embody, and show how
a XDAC System would be effectively used in modern day computing.
}
comment = {
Senior Honors Thesis. Advisor: Ed Feustel.
}
}
@TechReport{Dartmouth:TR2004-505,
author = {David Kotz },
title = {{Technological Implications for Privacy}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-505},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/369/TR2004-505.pdf},
abstract = {
The World-Wide Web is increasingly used for commerce and access to personal information
stored in databases. Although the Web is ``just another medium'' for information
exchange, the fact that all the information is stored in computers, and all of the
activity happens in computers and computer networks, makes it easier (cheaper) than
every to track users' activities. By recording and analyzing user's activities in
the Web, activities that may seem to be quite private to many users, it is more
likely than ever before that a person's privacy may be threatened. In this paper
I examine some of the technology in the Web, and how it affects the privacy of Web
users. I also briefly summarize some of the efforts to regulate privacy on the Internet.
}
comment = {
Originally written in 1998; this revision was dated January 3, 1999. The work was
unofficially released, then made a Technical Report noin June 2004.
}
}
@TechReport{Dartmouth:TR2004-504,
author = {Calvin Newport },
title = {{Simulating mobile ad hoc networks: a quantitative evaluation of common MANET simulation models}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-504},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/368/TR2004-504.pdf},
abstract = {
Because it is difficult and costly to conduct real-world mobile ad hoc network experiments,
researchers commonly rely on computer simulation to evaluate their routing protocols.
However, simulation is far from perfect. A growing number of studies indicate that
simulated results can be dramatically affected by several sensitive simulation parameters.
It is also commonly noted that most simulation models make simplifying assumptions
about radio behavior. This situation casts doubt on the reliability and applicability
of many ad hoc network simulation results.
In this study, we begin with a large outdoor routing experiment testing the performance
of four popular ad hoc algorithms (AODV, APRL, ODMRP, and STARA). We present a detailed
comparative analysis of these four implementations. Then, using the outdoor results
as a baseline of reality, we disprove a set of common assumptions used in simulation
design, and quantify the impact of these assumptions on simulated results. We also
more specifically validate a group of popular radio models with our real-world data,
and explore the sensitivity of various simulation parameters in predicting accurate
results. We close with a series of specific recommendations for simulation and ad
hoc routing protocol designers.
}
comment = {
Senior Honors Thesis. Advisor: David Kotz.
}
}
@TechReport{Dartmouth:TR2004-503,
author = {Joseph E. Pechter },
title = {{Enhancing Expressiveness of Speech through Animated Avatars for Instant Messaging and Mobile Phones}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-503},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/367/TR2004-503.pdf},
abstract = {
This thesis aims to create a chat program that allows users to communicate via an
animated avatar that provides believable lip-synchronization and expressive emotion.
Currently many avatars do not attempt to do lip-synchronization. Those that do are
not well synchronized and have little or no emotional expression. Most avatars with
lip synch use realistic looking 3D models or stylized rendering of complex models.
This work utilizes images rendered in a cartoon style and lip-synchronization rules
based on traditional animation. The cartoon style, as opposed to a more realistic
look, makes the mouth motion more believable and the characters more appealing.
The cartoon look and image-based animation (as opposed to a graphic model animated
through manipulation of a skeleton or wireframe) also allows for fewer key frames
resulting in faster speed with more room for expressiveness. When text is entered
into the program, the Festival Text-to-Speech engine creates a speech file and extracts
phoneme and phoneme duration data. Believable and fluid lip-synchronization is then
achieved by means of a number of phoneme-to-image rules. Alternatively, phoneme
and phoneme duration data can be obtained for speech dictated into a microphone
using Microsoft SAPI and the CSLU Toolkit. Once lip synchronization has been completed,
rules for non-verbal animation are added. Emotions are appended to the animation
of speech in two ways: automatically, by recognition of key words and punctuation,
or deliberately, by user-defined tags. Additionally, rules are defined for idle-time
animation. Preliminary results indicate that the animated avatar program offers
an improvement over currently available software. It aids in the understandability
of speech, combines easily recognizable and expressive emotions with speech, and
successfully enhances overall enjoyment of the chat experience. Applications for
the program include use in cell phones for the deaf or hearing impaired, instant
messaging, video conferencing, instructional software, and speech and animation
synthesis.
}
comment = {
Senior Honors Thesis. Advisors: Lorie Loeb, Hany Farid, Stephen Linder
}
}
@TechReport{Dartmouth:TR2004-502,
author = {Geoffrey H. Stowe },
title = {{A Secure Network Node Approach to the Policy Decision Point in Distributed Access Control}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-502},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/366/TR2004-502.pdf},
abstract = {
To date, the vast majority of access control research and development has been on
gathering, managing, and exchanging information about users. But an equally important
component which has yet to be fully developed is the Policy Decision Point - the
system that decides whether an access request should be granted given certain attributes
of the requestor. This paper describes the research and implementation of a new
PDP system for an undergraduate honors project. This PDP system employs three unique
features which differentiate it from existing technology: collaboration capabilities,
trusted management, and interoperability with other access control systems. Security
considerations and future research areas are also discussed.
}
comment = {
Senior Honors Thesis. Advisor: Ed Feustel
}
}
@TechReport{Dartmouth:TR2004-501,
author = {William Pechter },
title = {{Synchronizing Keyframe Facial Animation to Multiple Text-to-Speech Engines and Natural Voice with Fast Response Time}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-501},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/365/TR2004-501.pdf},
abstract = {
This thesis aims to create an automated lip-synchronization system for real-time
applications. Specifically, the system is required to be fast, consist of a limited
number of keyframes with small memory requirements, and create fluid and believable
animations that synchronize with text-to-speech engines as well as raw voice data.
The algorithms utilize traditional keyframe animation and a novel method of keyframe
selection. Additionally, phoneme-to-keyframe mapping, synchronization, and simple
blending rules are employed. The algorithms provide blending between keyframe images,
borrow information from neighboring phonemes, accentuate phonemes b, p and m, differentiate
between keyframes for phonemes with allophonic variations, and provide prosodromic
variation by including emotion while speaking. The lip-sync animation synchronizes
with multiple synthesized voices and human speech. A fast and versatile online real-time
java chat interface is created to exhibit vivid facial animation.
Results show that the animation algorithms are fast and show accurate lip-synchronization.
Additionally, surveys showed that the animations are visually pleasing and improve
speech understandability 96% of the time. Applications for this project include
internet chat capabilities, interactive teaching of foreign languages, animated
news broadcasting, enhanced game technology, and cell phone messaging.
}
comment = {
Senior Honors Thesis. Advisors: Lorie Loeb, Hany Farid, and Stephen Linder
}
}
@TechReport{Dartmouth:TR2004-500,
author = {Brunn W. Roysden },
title = {{Scheduling Pipelined, Multi-Threaded Programs in Linux}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-500},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/364/TR2004-500.pdf},
abstract = {
A process causes latency when it performs I/O or communication. Pipelined processes
mitigate latency by concurrently executing multiple threads--- sequences of operations---
and overlapping computation, communication, and I/O. When more than one thread is
ready to run, the scheduler determines which thread in fact runs. This paper presents
techniques for scheduling pipelines, with the following three findings.
First, using Linux kernel version 2.6 and the NPTL threads package, we observe a
3-6% performance improvement over kernel version 2.4 and the LinuxThreads package.
Second, we test techniques that both take advantage of prior knowledge about whether
a program is I/O-bound or compute-bound and raise and lower priorities before the
pipeline begins working. These techniques, referred to as fixed scheduling, further
improve performance by 5% in the case of the compute-bound columnsort algorithm.
In the I/O-bound algorithm, fixed scheduling failed to yield better performance
than the default scheduling.
Third, we test simple, adjusting methods that do not take advantage of prior knowledge
about whether a program in compute-bound or I/O-bound but rather adjust scheduling
as the pipeline progresses. These techniques, called adjusting scheduling, fail
to yield better performance than the default scheduling in any of our test cases.
In addition, we suggest new scheduling calls and other operating-system improvements.
}
comment = {
Senior honors thesis; advisor: Tom Cormen.
}
}
@TechReport{Dartmouth:TR2004-499,
author = {Nikita E Dubrovsky },
title = {{Mobile Agents Simulation with DaSSF}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-499},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/363/TR2004-499.pdf},
abstract = {
Mobile agents are programs that can migrate from machine to machine in a network
of computers and have complete control over their movement. Since the performance
space of mobile agents has not been characterized fully, assessing the effectiveness
of using mobile agents over a traditional client/server approach currently requires
implementing an agent system and running time-consuming experiments.
This report presents a simple mobile-agent simulation that can provide quick information
on the performance and scalability of a generic information retrieval (IR) mobile-agent
system under different network configurations. The simulation is built using the
DaSSF and DaSSFNet frameworks, resulting in high performance and great configuration
flexibility. This report also implements a real D'Agents mobile-agent IR system,
measuring the performance of the system. A comparison of these real-world performance
results and those given by the simulation suggest that the simulation has good accuracy
in predicting the scalability of a mobile-agent system. Thus this report argues
that simulation provides a good way to quickly assess the performance and scalability
of an IR mobile-agent system under different network configurations.
}
comment = {
Senior Honors Thesis. Advisor: Bob Gray.
}
}
@TechReport{Dartmouth:TR2004-498,
author = {Rachel B. Ringel },
title = {{Efficient Wait-Free Implementation of Atomic Multi-Word Buffer}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-498},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/362/TR2004-498.pdf},
abstract = {
This thesis proposes algorithms for implementing a atomic multi-word buffer, which
can be accessed concurrently by multiple readers and a single writer, from the hardware-supported
shared memory. The algorithms are required to be wait-free: each process reads or
writes the multi-word buffer in a bounded number of its own steps, regardless of
whether other processes are fast, slow or have crashed. Our first algorithm is
built from multi-writer, multi-reader variables whereas the second algorithm is
built from single-writer, multi-reader variables. For either algorithm, the worst-case
running time of a read or a write operation on the m-word buffer is O(m). The space
complexity of the algorithms is O(mn). Neither algorithm requires hardware support
for any special synchronization instructions; the ability to read or write into
any machine word is sufficient. The algorithms significantly improve on Peterson's
algorithm, which has O(mn) time complexity for the write operation on the buffer.
}
comment = {
Senior Honors Thesis. Advisor: Prasad Jayanti.
}
}
@TechReport{Dartmouth:TR2004-497,
author = {Darren Erik Vengroff and David Kotz },
title = {{A Holesome File System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-497},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/361/TR2004-497.pdf},
abstract = {
We present a novel approach to fully dynamic management of physical disk blocks in
Unix file systems. By adding a single system call, zero, to an existing file system,
we permit applications to create holes, that is, regions of files to which no physical
disk blocks are allocated, far more flexibly than previously possible. zero can
create holes in the middle of existing files.
Using zero, it is possible to efficiently implement applications including a variety
of databases and I/O-efficient computation systems on top of the Unix file system.
zero can also be used to implement an efficient file-system-based paging mechanism.
In some I/O-efficient computations, the availability of zero effectively doubles
disk capacity by allowing blocks of temporary files to be reallocated to new files
as they are read.
Experiments on a Linux ext2 file system augmented by zero demonstrate that where
their functionality overlaps, zero is more efficient than ftruncate(). Additional
experiments reveal that in exchange for added effective disk capacity, I/O-efficient
code pays only a small performance penalty.
}
comment = {
This paper was written in July 1995, but sat unpublished until May 2004 when it was
released as this technical report, unchanged.
}
}
@TechReport{Dartmouth:TR2004-496,
author = {Tristan Henderson and David Kotz and Ilya Abyzov },
title = {{The Changing Usage of a Mature Campus-wide Wireless Network}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-496},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/360/TR2004-496.pdf},
abstract = {
Wireless Local Area Networks (WLANs) are now common on academic and corporate campuses.
As ``Wi-Fi'' technology becomes ubiquitous, it is increasingly important to understand
trends in the usage of these networks.
This paper analyzes an extensive network trace from a mature 802.11 WLAN, including
more than 550 access points and 7000 users over seventeen weeks. We employ several
measurement techniques, including syslogs, telephone records, SNMP polling and tcpdump
packet sniffing. This is the largest WLAN study to date, and the first to look at
a large, mature WLAN and consider geographic mobility. We compare this trace to
a trace taken after the networks initial deployment two years ago.
We found that the applications used on the WLAN changed dramatically. Initial WLAN
usage was dominated by Web traffic; our new trace shows significant increases in
peer-to-peer, streaming multimedia, and voice over IP (VoIP) traffic. On-campus
traffic now exceeds offcampus traffic, a reversal of the situation at the WLANs
initial deployment. Our study indicates that VoIP has been used little on the wireless
network thus far, and most VoIP calls are made on the wired network. Most calls
last less than a minute.
We saw more heterogeneity in the types of clients used, with more embedded wireless
devices such as PDAs and mobile VoIP clients. We define a new metric for mobility,
the ``session diameter.'' We use this metric to show that embedded devices have
different mobility characteristics than laptops, and travel further and roam to
more access points. Overall, users were surprisingly non-mobile, with half remaining
close to home about 98% of the time.
}
comment = {
A revised version will appear in Mobicom 2004. See also http://www.cs.dartmouth.edu/~campus/.
}
}
@TechReport{Dartmouth:TR2004-495,
author = {Guanling Chen and David Kotz },
title = {{Dependency management in distributed settings}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-495},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/359/TR2004-495.pdf},
abstract = {
Ubiquitous-computing environments are heterogeneous and volatile in nature. Systems
that support ubicomp applications must be self-managed, to reduce human intervention.
In this paper, we present a general service that helps distributed software components
to manage their dependencies. Our service proactively monitors the liveness of components
and recovers them according to supplied policies. Our service also tracks the state
of components, on behalf of their dependents, and may automatically select components
for the dependent to use based on evaluations of customized functions. We believe
that our approach is flexible and abstracts away many of the complexities encountered
in ubicomp environments. In particular, we show how we applied the service to manage
dependencies of context-fusion operators and present some experimental results.
}
comment = {
A short 2-page poster abstract of this work appears in the International Conference
on Autonomic Computing (ICAC-04), May 2004.
}
}
@TechReport{Dartmouth:TR2004-494,
author = {Christopher J. Langmead and Bruce R. Donald },
title = {{An Improved Nuclear Vector Replacement Algorithm for Nuclear Magnetic Resonance Assignment}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-494},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/358/TR2004-494.pdf},
abstract = {
We report an improvement to the Nuclear Vector Replacement (NVR) algorithm for high-throughput
Nuclear Magnetic Resonance (NMR) resonance assignment. The new algorithm improves
upon our earlier result in terms of accuracy and computational complexity. In particular,
the new NVR algorithm assigns backbone resonances without error (100% accuracy)
on the same test suite examined in [Langmead and Donald J. Biomol. NMR 2004], and
runs in $O(n^{5/2} log {(cn)})$ time where $n$ is the number of amino acids in the
primary sequence of the protein, and $c$ is the maximum edge weight in an integer-weighted
bipartite graph.
}
}
@TechReport{Dartmouth:TR2004-493,
author = {Javed Aslam and Sergey Bratus and David Kotz and Ron Peterson and Daniela Rus and Brett Tofel },
title = {{The Kerf toolkit for intrusion analysis}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-493},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/357/TR2004-493.pdf},
abstract = {
We consider the problem of intrusion analysis and present the Kerf Toolkit, whose
purpose is to provide an efficient and flexible infrastructure for the analysis
of attacks. The Kerf Toolkit includes a mechanism for securely recording host and
network logging information for a network of workstations, a domain-specific language
for querying this stored data, and an interface for viewing the results of such
a query, providing feedback on these results, and generating new queries in an iterative
fashion. We describe the architecture of Kerf, present examples to demonstrate the
power of our query language, and discuss the performance of our implementation of
this system.
}
}
@TechReport{Dartmouth:TR2004-492,
author = {Ryan H. Lilien and Mohini Sridharan and Bruce R. Donald },
title = {{Identification of Novel Small Molecule Inhibitors of Core-Binding Factor Dimerization by Computational Screening against NMR Molecular Ensembles}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-492},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/356/TR2004-492.pdf},
abstract = {
The long development process of novel pharmaceutical compounds begins with the identification
of a lead inhibitor compound. Computational screening to identify those ligands,
or small molecules, most likely to inhibit a target protein may benefit the pharmaceutical
development process by reducing the time required to identify a lead compound. Typically,
computational ligand screening utilizes high-resolution structural models of both
the protein and ligand to fit or `dock' each member of a ligand database into the
binding site of the protein. Ligands are then ranked by the number and quality of
interactions formed in the predicted protein-ligand complex. It is currently believed
that proteins in solution do not assume a single rigid conformation but instead
tend to move through a small region of conformation space. Therefore, docking ligands
against a static snapshot of protein structure has predictive limitations because
it ignores the inherent flexibility of the protein. A challenge, therefore, has
been the development of docking algorithms capable of modeling protein flexibility
while balancing computational feasibility. In this paper, we present our initial
development and work on a molecular ensemble-based algorithm to model protein flexibility
for protein-ligand binding prediction. First, a molecular ensemble is generated
from molecular structures satisfying experimentally-measured NMR constraints. Second,
traditional protein-ligand docking is performed on each member of the protein's
molecular ensemble. This step generates lists of ligands predicted to bind to each
individual member of the ensemble. Finally, lists of top predicted binders are consolidated
to identify those ligands predicted to bind multiple members of the protein's molecular
ensemble. We applied our algorithm to identify inhibitors of Core Binding Factor
(CBF) among a subset of approximately 70,000 ligands of the Available Chemicals
Directory. Our 26 top-predicted binding ligands are currently being tested experimentally
in the wetlab by both NMR-binding experiments (15N-edited Heteronuclear Single-Quantum
Coherence (HSQC)) and Electrophoretic Gel Mobility Shift Assays (EMSA). Preliminary
results indicate that of approximately 26 ligands tested, three induce perturbations
in the protein's NMR chemical shifts indicative of ligand binding and one ligand
(2-amino-5-cyano-4-tertbutyl thiazole) causes a band pattern in the EMSA indicating
the disruption of CBF dimerization.
}
}
@TechReport{Dartmouth:TR2004-491,
author = {Libo Song and David Kotz and Ravi Jain and Xiaoning He },
title = {{Evaluating next-cell predictors with extensive Wi-Fi mobility data}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-491},
year = {2004},
month = {January},
abstract = {
Location is an important feature for many applications, and wireless networks can
better serve their clients by anticipating client mobility. As a result, many location
predictors have been proposed in the literature, though few have been evaluated
with empirical evidence. This paper reports on the results of the first extensive
empirical evaluation of location predictors, using a two-year trace of the mobility
patterns of over 6,000 users on Dartmouth's campus-wide Wi-Fi wireless network.
We implemented and compared the prediction accuracy of several location predictors
drawn from four major families of domain-independent predictors, namely Markov-based,
compression-based, PPM, and SPM predictors. We found that low-order Markov predictors
performed as well or better than the more complex and more space-consuming compression-based
predictors. Predictors of both families fail to make a prediction when the recent
context has not been previously seen. To overcome this drawback, we added a simple
fallback feature to each predictor and found that it significantly enhanced its
accuracy in exchange for modest effort. Thus the Order-2 Markov predictor with fallback
was the best predictor we studied, obtaining a median accuracy of about 72% for
users with long trace lengths. We also investigated a simplification of the Markov
predictors, where the prediction is based not on the most frequently seen context
in the past, but the most recent, resulting in significant space and computational
savings. We found that Markov predictors with this recency semantics can rival the
accuracy of standard Markov predictors in some cases. Finally, we considered several
seemingly obvious enhancements, such as smarter tie-breaking and aging of context
information, and discovered that they had little effect on accuracy. The paper ends
with a discussion and suggestions for further work.
}
comment = {
PDF removed because this version was superceded by the later journal version, and
per IEEE rules we can only post the final version. A revised version of this paper
appeared in IEEE TMC 5(12), pp. 1633-1649, December 2006. An earlier (and shorter)
version of this paper appeared at IEEE Infocom, March 7-11, 2004.
}
}
@TechReport{Dartmouth:TR2004-490,
author = {Guanling Chen and David Kotz },
title = {{A Case Study of Four Location Traces}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-490},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/354/TR2004-490.pdf},
abstract = {
Location is one of the most important context information that an ubiquitous-computing
application may leverage. Thus understanding the location systems and how location-aware
applications interact with them is critical for design and deployment of both the
location systems and location-aware applications. In this paper, we analyze a set
of traces collected from two small-scale one-building location system and two large-scale
campus-wide location systems. Our goal is to study characteristics of these location
systems ant how these factors should be taken into account by a potentially large
number of location-aware applications with different needs. We make empirical measurements
of several important metrics and compare the results across these location systems.
We discuss the implication of these results on location-aware applications and their
supporting software infrastructure, and how location systems could be improved to
better serve applications' needs. In places where possible, we use location-aware
applications discussed in existing literatures as illustrating examples.
}
}
@TechReport{Dartmouth:TR2004-489,
author = {John Marchesini and Sean W. Smith and Meiyuan Zhao },
title = {{Keyjacking: The Surprising Insecurity of Client-side SSL}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-489},
year = {2013},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/353/TR2004-489.pdf},
abstract = {
In theory, PKI can provide a flexible and strong way to authenticate users in distributed
information systems. In practice, much is being invested in realizing this vision
via client-side SSL and various client keystores. However, whether this works depends
on whether what the machines do with the private keys matches what the humans think
they do: whether a server operator can conclude from an SSL request authenticated
with a user's private key that the user was aware of and approved that request.
Exploring this vision, we demonstrate via a series of experiments that this assumption
does not hold with standard desktop tools, even if the browser user does all the
right things. A fundamental rethinking of the trust, usage, and storage model might
result in more effective tools for achieving the PKI vision.
}
comment = {
This TR supercedes TR2003-443. A preliminary version appeared in the proceedings
of the 2nd Annual PKI Research Workshop in April of 2003.
}
}
@TechReport{Dartmouth:TR2004-488,
author = {Guanling Chen and David Kotz },
title = {{Application-controlled loss-tolerant data dissemination}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-488},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/352/TR2004-488.pdf},
abstract = {
Reactive or proactive mobile applications require continuous monitoring of their
physical and computational environment to make appropriate decisions in time. These
applications need to monitor data streams produced by sensors and react to changes.
When mobile sensors and applications are connected by low-bandwidth wireless networks,
sensor data rates may overwhelm the capacity of network links or of the applications.
In traditional networks and distributed systems, flow-control and congestion-control
policies either drop data or force the sender to pause. When the data sender is
sensing the physical environment, however, a pause is equivalent to dropping data.
Arbitrary data drops are not necessarily acceptable to the reactive mobile applications
receiving sensor data. Data distribution systems must support application-specific
policies that selectively drop data objects when network or application buffers
overflow.
In this paper we present a data-dissemination service, PACK, which allows applications
to specify customized data-reduction policies. These policies define how to discard
or summarize data flows wherever buffers overflow on the dissemination path, notably
at the mobile hosts where applications often reside. The PACK service provides an
overlay infrastructure to support mobile data sources and sinks, using application-specific
data-reduction policies where necessary along the data path. We uniformly apply
the data-stream ``packing'' abstraction to buffer overflow caused by network congestion,
slow receivers, and the temporary disconnections caused by end-host mobility. We
demonstrate the effectiveness of our approach with an application example and experimental
measurements.
}
}
@TechReport{Dartmouth:TR2004-487,
author = {Christopher J. Langmead and Bruce R. Donald },
title = {{High-Throughput 3D Homology Detection via NMR Resonance Assignment}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-487},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/351/TR2004-487.pdf},
abstract = {
One goal of the structural genomics initiative is the identification of new protein
folds. Sequence-based structural homology prediction methods are an important means
for prioritizing unknown proteins for structure determination. However, an important
challenge remains: two highly dissimilar sequences can have similar folds --- how
can we detect this rapidly, in the context of structural genomics? High-throughput
NMR experiments, coupled with novel algorithms for data analysis, can address this
challenge. We report an automated procedure, called HD, for detecting 3D structural
homologies from sparse, unassigned protein NMR data. Our method identifies 3D models
in a protein structural database whose geometries best fit the unassigned experimental
NMR data. HD does not use, and is thus not limited by sequence homology. The method
can also be used to confirm or refute structural predictions made by other techniques
such as protein threading or homology modelling. The algorithm runs in $O(pn^{5/2}
log {(cn)} + p log p)$ time, where $p$ is the number of proteins in the database,
$n$ is the number of residues in the target protein and $c$ is the maximum edge
weight in an integer-weighted bipartite graph. Our experiments on real NMR data
from 3 different proteins against a database of 4,500 representative folds demonstrate
that the method identifies closely related protein folds, including sub-domains
of larger proteins, with as little as 10-30% sequence homology between the target
protein (or sub-domain) and the computed model. In particular, we report no false-negatives
or false-positives despite significant percentages of missing experimental data.
}
comment = {
A revised version of this paper will appear in the IEEE Computational Systems
Bioinformatics Conference (CSB), Stanford CA. (August, 2004).
}
}
@TechReport{Dartmouth:TR2004-486,
author = {Jue Wang and Guanling Chen and David Kotz },
title = {{A meeting detector and its applications}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-486},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/350/TR2004-486.pdf},
abstract = {
In this paper we present a context-sensing component that recognizes meetings in
a typical office environment. Our prototype detects the meeting start and end by
combining outputs from pressure and motion sensors installed on the chairs. We developed
a telephone controller application that transfers incoming calls to voice-mail when
the user is in a meeting. Our experiments show that it is feasible to detect high-level
context changes with ``good enough'' accuracy, using low-cost, off-the-shelf hardware,
and simple algorithms without complex training. We also note the need for better
metrics to measure context detection performance, other than just accuracy. We propose
several metrics appropriate for our application in this paper. It may be useful,
however, for the community to define a set of general metrics as a basis to compare
different approaches of context detection.
}
}
@TechReport{Dartmouth:TR2004-485,
author = {Sidharth Nazareth and Sean Smith },
title = {{Using SPKI/SDSI for Distributed Maintenance of Attribute Release Policies in Shibboleth}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-485},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/349/TR2004-485.pdf},
abstract = {
The Shibboleth middleware from Internet2 provides a way for users at higher-education
institutions to access remote electronic content in compliance with the inter-institutional
license agreements that govern such access. To protect end-user privacy, Shibboleth
permits users to construct attribute release policies that control what user credentials
a given content provider can obtain. However, Shibboleth leaves unspecified how
to construct these policies.
To be effective, a solution needs to accommodate the typical nature of a university:
a set of decentralized fiefdoms. This need argues for a public-key infrastructure
(PKI) approach---since public-key cryptography does not require parties to agree
on a secret beforehand, and parties distributed throughout the institution are unlikely
to agree on anything. However, this need also argues against the strict hierarchical
structure of traditional PKI---policy in different fiefdoms will be decided differently,
and originate within the fiefdom, rather than from an overall root.
This paper presents our design and prototype of a system that uses the decentralized
public-key framework of SPKI/SDSI to solve this problem.
}
}
@TechReport{Dartmouth:TR2004-484,
author = {Sean Smith and Nicholas C. Goffee and Sung Hoon Kim and Punch Taylor and Meiyuan Zhao and John Marchesini },
title = {{Greenpass: Flexible and Scalable Authorization for Wireless Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2004-484},
year = {2004},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/348/TR2004-484.pdf},
abstract = {
Wireless networks break the implicit assumptions that supported authorization in
wired networks (that is: if one could connect, then one must be authorized). However,
ensuring that only authorized users can access a campus-wide wireless network creates
many challenges: we must permit authorized guests to access the same network resources
that internal users do; we must accommodate the de-centralized way that authority
flows in real universities; we also must work within standards, and accommodate
the laptops and systems that users already have, without requiring additional software
or plug-ins.
This paper describes our ongoing project to address this problem, using SPKI/SDSI
delegation on top of X.509 keypair within EAP-TLS. Within the ``living laboratory''
of Dartmouth's wireless network, this project lets us solve real problem with wireless
networking, while also experimenting with trust flows and testing the limits of
current tools.
}
}
@TechReport{Dartmouth:TR2003-481,
author = {Ryan H. Lilien and Chris Bailey-Kellogg and Amy A. Anderson and Bruce R. Donald },
title = {{A Subgroup Algorithm to Identify Cross-Rotation Peaks Consistent with Non-Crystallographic Symmetry}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-481},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/347/TR2003-481.pdf},
abstract = {
Molecular replacement (MR) often plays a prominent role in determining initial phase
angles for structure determination by X-ray crystallography. In this paper, an efficient
quaternion-based algorithm is presented for analyzing peaks from a cross-rotation
function to identify model orientations consistent with non-crystallographic symmetry
(NCS), and to generate NCS-consistent orientations missing from the list of cross-rotation
peaks. Our algorithm, CRANS, analyzes the rotation differences between each pair
of cross-rotation peaks to identify finite subgroups of NCS. Sets of rotation differences
satisfying the subgroup axioms correspond to orientations compatible with the correct
NCS. The CRANS algorithm was first tested using cross-rotation peaks computed from
structure factor data for three test systems, and then used to assist in the de
novo structure determination of dihydrofolate reductase-thymidylate synthase (DHFR-TS)
from Cryptosporidium hominis. In every case, the CRANS algorithm runs in seconds
to identify orientations consistent with the observed NCS and to generate missing
orientations not present in the cross-rotation peak list. The CRANS algorithm has
application in every molecular replacement phasing effort with NCS.
}
comment = {
A revised version of this paper has been accepted for publication and will appear
in the journal Acta Crystallographica D: Biological Crystallography.
In press (2004).
}
}
@TechReport{Dartmouth:TR2003-480,
author = {Tristan Henderson and David Kotz },
title = {{Problems with the Dartmouth wireless SNMP data collection}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-480},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/346/TR2003-480-rev3.pdf},
abstract = {
The original Dartmouth wireless network study used SNMP to query the college's Cisco
802.11b access points. The perl scripts that performed the SNMP queries suffered
from some problems, in that they queried inappropriate SNMP values, or misunderstood
the meaning of other values. This data was also used in a subsequent analysis. The
same scripts were used to collect data for a subsequent study of another wireless
network. This document outlines these problems and indicates which of the data collected
by the original scripts may be invalid.
}
comment = {
See http://www.cs.dartmouth.edu/~campus/ for more information. Revision 2 of 12/31/03
reflects updated information about the Balazinska paper. Revision 3 of 10/29/04
reflects a difference between the preliminary and final version of the Kotz/Essien
journal paper.
}
}
@TechReport{Dartmouth:TR2003-476,
author = {John Marchesini and Sean W. Smith and Omen Wild and Rich MacDonald },
title = {{Experimenting with TCPA/TCG Hardware, Or: How I Learned to Stop Worrying and Love The Bear}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-476},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/345/TR2003-476.pdf},
abstract = {
Over the last few years, our group has been working on applications of secure coprocessors---but
has been frustrated by the limited computational environment and high expense of
such devices. Over the last few years, the TCPA (now TCG) has produced a specification
for a trusted platform module (TPM)---a small hardware addition intended to improve
the overall security of a larger machine (and tied up with a still-murky vision
of Windows-based trusted computing). Some commodity desktops now come up with these
TPMs.
Consequently, we began an experiment to see if (in the absence of a Non-Disclosure
Agreement) we could use this hardware to transform a desktop Linux machine into
a virtual secure coprocessor: more powerful but less secure than higher-end devices.
This experiment has several purposes: to provide a new platform for secure coprocessor
applications, to see how well the TCPA/TCG approach works, and (by working in open
source) to provide a platform for the broader community to experiment with alternative
architectures in the contentious area of trusted computing.
This paper reports what we have learned so far: the approach is feasible, but effective
deployment requires a more thorough look at OS security.
}
comment = {
This report, TR2003-476, supersedes TR2003-471 of August 2003. Furthermore, the December
15, 2003 version of TR2003476 fixes typos found in the December 4, 2003 version.
}
}
@TechReport{Dartmouth:TR2003-475,
author = {King Y. Tan },
title = {{On the Complexity of Implementing Certain Classes of Shared Objects}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-475},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/344/TR2003-475.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/344/TR2003-475.pdf},
abstract = {
We consider shared memory systems in which asynchronous processes cooperate with
each other by communicating via shared data objects, such as counters, queues, stacks,
and priority queues. The common approach to implementing such shared objects is
based on locking: To perform an operation on a shared object, a process obtains
a lock, accesses the object, and then releases the lock. Locking, however, has several
drawbacks, including convoying, priority inversion, and deadlocks. Furthermore,
lock-based implementations are not fault-tolerant: if a process crashes while holding
a lock, other processes can end up waiting forever for the lock. Wait-free linearizable
implementations were conceived to overcome most of the above drawbacks of locking.
A wait-free implementation guarantees that if a process repeatedly takes steps,
then its operation on the implemented data object will eventually complete, regardless
of whether other processes are slow, or fast, or have crashed. In this thesis, we
first present an efficient wait-free linearizable implementation of a class of object
types, called closed and closable types, and then prove time and space lower bounds
on wait-free linearizable implementations of another class of object types, called
perturbable types. (1) We present a wait-free linearizable implementation of n-process
closed and closable types (such as swap, fetch&add, fetch&multiply, and fetch&L,
where L is any of the boolean operations and, or, or complement) using registers
that support load-link (LL) and store-conditional (SC) as base objects. The time
complexity of the implementation grows linearly with contention, but is never more
than O(log ^2 n). We believe that this is the first implementation of a class of
types (as opposed to a specific type) to achieve a sub-linear time complexity. (2)
We prove linear time and space lower bounds on the wait-free linearizable implementations
of n-process perturbable types (such as increment, fetch&add, modulo k counter,
LL/SC bit, k-valued compare&swap (for any k >= n), single-writer snapshot) that
use resettable consensus and historyless objects (such as registers that support
read and write) as base objects. This improves on some previously known Omega(sqrt{n})
space complexity lower bounds. It also shows the near space optimality of some known
wait-free linearizable implementations.
}
}
@TechReport{Dartmouth:TR2003-474,
author = {Anthony K. Yan and Christopher J. Langmead and Bruce Randall Donald },
title = {{A Probability-Based Similarity Measure for Saupe Alignment Tensors with Applications to Residual Dipolar Couplings in NMR Structural Biology}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-474},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/343/TR2003-474.pdf},
abstract = {
High-throughput NMR structural biology and NMR structural genomics pose a fascinating
set of geometric challenges. A key bottleneck in NMR structural biology is the resonance
assignment problem. We seek to accelerate protein NMR resonance assignment and structure
determination by exploiting a priori structural information. In particular,
a method known as Nuclear Vector Replacement (NVR) has been proposed as a method
for solving the assignment problem given a priori structural information [24,25].
Among several different kinds of input data, NVR uses a particular type of NMR data
known as residual dipolar couplings (RDCs). The basic physics of residual
dipolar couplings tells us that the data should be explainable by a structural model
and set of parameters contained within the Saupe alignment tensor.
In the NVR algorithm, one estimates the Saupe alignment tensors and then proceeds
to refine those estimates. We would like to quantify the accuracy of such estimates,
where we compare the estimated Saupe matrix to the correct Saupe matrix. In this
work, we propose a way to quantify this comparison. Given a correct Saupe matrix
and an estimated Saupe matrix, we compute an upper bound on the probability that
a randomly rotated Saupe tensor would have an error smaller than the estimated Saupe
matrix. This has the advantage of being a quantified upper bound which also has
a clear interpretation in terms of geometry and probability. While the specific
application of our rotation probability results is given to NVR, our novel methods
can be used for any RDC-based algorithm to bound the accuracy of the estimated alignment
tensors. Furthermore, they could also be used in X-ray crystallography or molecular
docking to quantitate the accuracy of calculated rotations of proteins, protein
domains, nucleic acids, or small molecules.
}
comment = {
A revised and expanded version of this paper has been accepted at a journal and will
appear as: "A Probability-Based Similarity Measure for Saupe Alignment Tensors with
Applications to Residual Dipolar Couplings in NMR Structural Biology", in The International
Journal of Robotics Research Special Issue on Robotics Techniques Applied to
Computational Biology, 2004.
}
}
@TechReport{Dartmouth:TR2003-472,
author = {Libo Song and David Kotz and Ravi Jain and Xiaoning He },
title = {{Evaluating Location Predictors with Extensive Wi-Fi Mobility Data}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-472},
year = {2003},
month = {January},
comment = {
This report with this number was not released until 2004, so it was given a new
number and appeared as TR2004-491. A revised version was published as a short paper:
Libo Song, David Kotz, Ravi Jain, and Xiaoning He. Mobicom poster: Evaluating location
predictors with extensive Wi-Fi mobility data. ACM SIGMOBILE Mobile Computing and
Communication Review, 7(4):64-65, October 2003.
}
}
@TechReport{Dartmouth:TR2003-471,
author = {Rich MacDonald and Sean W. Smith and John Marchesini and Omen Wild },
title = {{Bear: An Open-Source Virtual Secure Coprocessor based on TCPA}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-471},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/341/TR2003-471.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/341/TR2003-471.pdf},
abstract = {
This paper reports on our ongoing project to use TCPA to transform a desktop Linux
machine into a virtual secure coprocessor: more powerful but less secure than higher-end
devices. We use TCPA hardware and modified boot loaders to protect fairly static
components, such as a trusted kernel; we use an enforcer module---configured as
Linux Security Module---to protected more dynamic system components; we use an encrypted
loopback filesystem to protect highly dynamic components.
All our code is open source and available under GPL from http://enforcer.sourceforge.net/
}
comment = {
Superceded by TR2003-476.
}
}
@TechReport{Dartmouth:TR2003-470,
author = {Anna M. Shubina and Sean W. Smith },
title = {{Using caching for browsing anonymity}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-470},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/340/TR2003-470.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/340/TR2003-470.pdf},
abstract = {
Privacy-providing tools, including tools that provide anonymity, are gaining popularity
in the modern world. Among the goals of their users is avoiding tracking and profiling.
While some businesses are unhappy with the growth of privacy-enhancing technologies,
others can use lack of information about their users to avoid unnecessary liability
and even possible harassment by parties with contrary business interests, and to
gain a competitive market edge.
Currently, users interested in anonymous browsing have the choice only between single-hop
proxies and the few more complex systems that are available. These still leave the
user vulnerable to long-term intersection attacks.
In this paper, we propose a caching proxy system for allowing users to retrieve
data from the World-Wide Web in a way that would provide recipient unobservability
by a third party and sender unobservability by the recipient and thus dispose with
intersection attacks, and report on the prototype we built using Google.
}
}
@TechReport{Dartmouth:TR2003-469,
author = {Bruce R. Donald and Craig McGray and Daniela Rus },
title = {{MEMS for Infosecurity}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-469},
year = {2003},
month = {January},
comment = {
Abstract and paper lost.
}
}
@TechReport{Dartmouth:TR2003-468,
author = {Heng Huang and Lea Wittie and Chris Hawblitzel },
title = {{Formal Properties of Linear Memory Types}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-468},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/338/TR2003-468.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/338/TR2003-468.pdf},
abstract = {
Efficient low-level systems need more control over memory than safe high-level languages
usually provide. As a result, run-time systems are typically written in unsafe languages
such as C. This report describes an abstract machine designed to give type-safe
code more control over memory. It includes complete definitions and proofs of preservation,
progress, strong normalization, erasure, and translation correctness.
}
}
@TechReport{Dartmouth:TR2003-467,
author = {David Kotz and Calvin Newport and Chip Elliott },
title = {{The mistaken axioms of wireless-network research}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-467},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/337/TR2003-467.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/337/TR2003-467.pdf},
abstract = {
Most research on ad-hoc wireless networks makes simplifying assumptions about radio
propagation. The ``Flat Earth'' model of the world is surprisingly popular: all
radios have circular range, have perfect coverage in that range, and travel on a
two-dimensional plane. CMU's ns-2 radio models are better but still fail to represent
many aspects of realistic radio networks, including hills, obstacles, link asymmetries,
and unpredictable fading. We briefly argue that key ``axioms'' of these types of
propagation models lead to simulation results that do not adequately reflect real
behavior of ad-hoc networks, and hence to network protocols that may not work well
(or at all) in reality. We then present a set of 802.11 measurements that clearly
demonstrate that these ``axioms'' are contrary to fact. The broad chasm between
simulation and reality calls into question many of results from prior papers, and
we summarize with a series of recommendations for researchers considering analytic
or simulation models of wireless networks.
}
comment = {
For more information related to this project see http://www.cs.dartmouth.edu/~campus/.
}
}
@TechReport{Dartmouth:TR2003-466,
author = {Siwei Lyu and Daniel Rockmore and Hany Farid },
title = {{Digital Art Forensics}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-466},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/336/TR2003-466.pdf},
abstract = {
We describe a computational technique for digitally authenticating works of art.
This approach builds statistical models of an artist from a set of authenticated
works. Additional works are then authenticated against this model. The statistical
model consists of first- and higher-order wavelet statistics. We show preliminary
results from our analysis of thirteen drawings by Pieter Bruegel the Elder. We also
present preliminary results showing how these techniques may be applicable to determining
how many hands contributed to a single painting.
}
}
@TechReport{Dartmouth:TR2003-465,
author = {Edward Wei },
title = {{Using Low Level Linear Memory Management for Type-Preserving Mark-Sweep Garbage Collector}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-465},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/335/TR2003-465.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/335/TR2003-465.pdf},
abstract = {
Efficient low-level systems such as garbage collectors need more control over memory
than safe high-level languages usually provide. Due to this constraint, garbage
collectors are typically written in unsafe languages such as C. A collector of this
form usually resides as a trusted primitive runtime service outside the model of
the programming language. The type safety of these languages depends on the assumption
that the garbage collector will not violate any typing invariants. However, no realistic
systems provide proof of this assumption.
A garbage collector written in a strongly typed language can guarantee not only
the safety of the garbage collector and the program being garbage collected (mutator),
but also the interaction between the collector and the mutator. Removing the garbage
collector from the trusted computing base has many additional benefits: Untrusted
code could be given more control over memory management without sacrificing security.
Low-level code such as device drivers could interface in a safe way with a garbage
collector. For these and the growing prevalence of garbage collectors in the typical
programming system necessitate a safe solution.
Previous research by Wang et al introduced a safe copying collector based on regions,
where the live graph structure of the heap is copied from an old region to a newer
region. This paper seeks to improve the efficiency of type-preserving garbage collection
with the introduction of a type-preserving mark and sweep garbage collector.
}
comment = {
Undergraduate Honors Thesis. Advisor: Chris Hawblitzel. Associated software release
at http://www.cs.dartmouth.edu/~hawblitz/
}
}
@TechReport{Dartmouth:TR2003-464,
author = {Li Shen and James Ford and Fillia Makedon and Andrew Saykin },
title = {{A Surface-based Approach for Classification of 3D Neuroanatomic Structures}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-464},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/334/TR2003-464.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/334/TR2003-464.pdf},
abstract = {
We present a new framework for 3D surface object classification that combines a powerful
shape description method with suitable pattern classification techniques. Spherical
harmonic parameterization and normalization techniques are used to describe a surface
shape and derive a dual high dimensional landmark representation. A point distribution
model is applied to reduce the dimensionality. Fisher's linear discriminants and
support vector machines are used for classification. Several feature selection schemes
are proposed for learning better classifiers. After showing the effectiveness of
this framework using simulated shape data, we apply it to real hippocampal data
in schizophrenia and perform extensive experimental studies by examining different
combinations of techniques. We achieve best leave-one-out cross-validation accuracies
of 93% (whole set, N=56) and 90% (right-handed males, N=39), respectively, which
are competitive with the best results in previous studies using different techniques
on similar types of data. Furthermore, to help medical diagnosis in practice, we
employ a threshold-free receiver operating characteristic (ROC) approach as an alternative
evaluation of classification results as well as propose a new method for visualizing
discriminative patterns.
}
}
@TechReport{Dartmouth:TR2003-463,
author = {Sanket Agrawal },
title = {{Investigation of Third Party Rights Service and Shibboleth Modification to Introduce the Service}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-463},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/333/TR2003-463.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/333/TR2003-463.pdf},
abstract = {
Shibboleth is an architecture to support inter-institutional sharing of electronic
resources that are subject to access control. Codifying copyright in Shibboleth
authorization policies is difficult because of the copyright exceptions which can
be highly subjective. Third Party Rights Service is a high-level concept that has
been suggested as a solution to approximate the exceptions of copyright law. In
this thesis, I investigate the components of the Third Party Rights Service. I design
and analyze a modified Shibboleth architecture based on these components. The resulting
architecture allows for the phased addition of the resources to make use of the
Third Party Rights Service, while keeping the existing resources in Shibboleth.
}
}
@TechReport{Dartmouth:TR2003-462,
author = {Zack Butler and Daniela Rus },
title = {{Distributed planning and control for modular robots with unit-compressible modules}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-462},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/332/TR2003-462.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/332/TR2003-462.pdf},
abstract = {
Self-reconfigurable robots are versatile systems consisting of large numbers of independent
modules. Effective use of these systems requires parallel actuation and planning,
both for efficiency and independence from a central controller. This paper presents
the PacMan algorithm, a technique for distributed actuation and planning for systems
with two- or three-dimensional unit-compressible modules. We give two versions of
the algorithm along with correctness analysis. We also analyze the parallel actuation
capability of the algorithm, showing that it will not deadlock and will avoid disconnecting
the robot. We have implemented PacMan on the Crystal robot, a hardware system developed
in our lab, and we present experiments and discuss the feasibility of large-scale
implementation.
}
}
@TechReport{Dartmouth:TR2003-461,
author = {Mindy J. Pereira },
title = {{Trusted S/MIME Gateways}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-461},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/331/TR2003-461.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/331/TR2003-461.pdf},
abstract = {
The utility of Web-based email clients is clear: a user is able to access their email
account from any computer anywhere at any time. However, this option is unavailable
to users whose security depends on their key pair being stored either on their local
computer or in their browser. Our implementation seeks to solve two problems with
secure email services. The first that of mobility: users must have access to their
key pairs in order to perform the necessary cryptographic operations. The second
is one of transition: initially, users would not want to give up their regular email
clients. Keeping these two restrictions in mind, we decided on the implementation
of a secure gateway system that works in conjunction with an existing mail server
and client. Our result is PKIGate, an S/MIME gateway that uses the DigitalNet (formerly
Getronics) S/MIME Freeware Library and IBM's 4758 secure coprocessor. This thesis
presents motivations for the project, a comparison with similar existing products,
software and hardware selection, the design, use case scenarios, a discussion of
implementation issues, and suggestions for future work.
}
comment = {
Senior Honors Thesis. Advisor: Sean Smith.
}
}
@TechReport{Dartmouth:TR2003-460,
author = {Elizabeth A. Hamon },
title = {{Enhancing Asynchronous Parallel Computing}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-460},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/330/TR2003-460.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/330/TR2003-460.pdf},
abstract = {
In applications using large amounts of data, hiding the latency inherent in accessing
data far from the processor is often necessary in order to achieve high performance.
Several researchers have observed that one way to address the challenge of latency
is by using a common structure: in a series of passes, the program reads in the
data, performs various operations on it, and writes out the data. Passes often consist
of a pipeline structure composed of different stages. In order to achieve high performance,
the stages are frequently overlapped, for example, by using asynchronous threads.
Out-of-core parallel programs provide one such example of this pattern. The development
and debugging time resulting from coordinating overlapping stages, however, can
be substantial. Moreover, modifying the structure of the overlap in an attempt to
achieve higher performance can require significant additional time on the part of
the programmer. This thesis presents FG, a Framework Generator designed to coordinate
the stages of a pipeline and allow the programmer to easily experiment with the
pipeline's structure, thus significantly reducing time to solution. We also discuss
preliminary results of using FG in an out-of-core sorting program.
}
}
@TechReport{Dartmouth:TR2003-459,
author = {Ron A. Oldfield },
title = {{Efficient I/O for Computational Grid Applications}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-459},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/329/TR2003-459.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/329/TR2003-459.pdf},
abstract = {
High-performance computing increasingly occurs on "computational grids" composed
of heterogeneous and geographically distributed systems of computers, networks,
and storage devices that collectively act as a single "virtual" computer. A key
challenge in this environment is to provide efficient access to data distributed
across remote data servers. This dissertation explores some of the issues associated
with I/O for wide-area distributed computing and describes an I/O system, called
Armada, with the following features: a framework to allow application and dataset
providers to flexibly compose graphs of processing modules that describe the distribution,
application interfaces, and processing required of the dataset before or after computation;
an algorithm to restructure application graphs to increase parallelism and to improve
network performance in a wide-area network; and a hierarchical graph-partitioning
scheme that deploys components of the application graph in a way that is both beneficial
to the application and sensitive to the administrative policies of the different
administrative domains. Experiments show that applications using Armada perform
well in both low- and high-bandwidth environments, and that our approach does an
exceptional job of hiding the network latency inherent in grid computing.
}
comment = {
This is a reformatted version of Ron Oldfield's Ph.D. dissertation. Unlike the dissertation
submitted to Dartmouth College, this version is single-spaced, uses 11pt fonts,
and is formatted specifically for double-sided printing.
}
}
@TechReport{Dartmouth:TR2003-458,
author = {Michael De Rosa },
title = {{Power Conservation in the Network Stack of Wireless Sensors}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-458},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/328/TR2003-458.pdf, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/328/TR2003-458.ps.Z},
abstract = {
Wireless sensor networks have recently become an incredibly active research area
in the networking community. Much attention has been given to the construction of
power-conserving protocols and techniques, as battery life is the one factor that
prevents successful wide-scale deployment of such networks. These techniques concentrate
on the optimization of network behavior, as the wireless transmission of data is
the most expensive operation performed by a sensor node. Very little work has been
published on the integration of such techniques, and their suitability to various
application domains. This paper presents an exhaustive power consumption analysis
of network stacks constructed with common algorithms, to determine the interactions
between such algorithms and the suitability of the resulting network stack for various
applications.
}
comment = {
Senior Honors Thesis. Advisor: Bob Gray.
}
}
@TechReport{Dartmouth:TR2003-457,
author = {Kunal Kain },
title = {{Electronic Documents and Digital Signatures}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-457},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/327/TR2003-457.pdf},
abstract = {
Often, the main motivation for using PKI in business environments is to streamline
workflow, by enabling humans to digitally sign electronic documents, instead of
manually signing paper ones. However, this application fails if adversaries can
construct electronic documents whose viewed contents can change in useful ways,
without invalidating the digital signature. In this paper, we examine the space
of such attacks, and describe how many popular electronic document formats and PKI
packages permit them.
}
comment = {
A revised version was published as follows:
K. Kain, S.W. Smith, R. Asokan.
"Digital
Signatures and Electronic Documents: A Cautionary Tale."
Advanced Communications
and Multimedia Security,
pp. 293-307, September 2002. Kluwer Academic Publishers.
http://portal.acm.org/citation.cfm?id=647802.737169
http://www.cs.dartmouth.edu/~sws/pubs/ksa02.pdf
}
}
@TechReport{Dartmouth:TR2003-456,
author = {Daniel F. Simola },
title = {{Discovery, Visualization and Analysis of Gene Regulatory Sequence Elements in Genomes}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-456},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/326/TR2003-456.pdf},
abstract = {
The advent of rapid DNA sequencing has produced an explosion in the amount of available
sequence information, permitting us to ask many new questions about DNA. There is
a pressing need to design algorithms that can provide answers to questions related
to the control of gene expression, and thus to the structure, function, and behavior
of organisms. Such algorithms must filter through massive amounts of informational
noise to identify meaningful conserved regulatory DNA sequence elements. We are
approaching these questions with the notion that visualization is a key to exploring
data relationships. Understanding the exact nature of these relationships can be
very difficult by simply interpreting raw data. The ability to look at data in a
graphical form allows us to apply our innate capacity to think visually to discern
the subtle relationships that might not be recognizable otherwise. This thesis
provides computational tools to visually identify and analyze candidate motifs in
the DNA of a species. This includes a parsing utility to store genomic data and
an application to search for and visually identify motifs. Using these tools, novel
and previously compiled gene sets were identified using the genome of the plant
species Arabidopsis thaliana.
}
comment = {
Senior Honors Thesis. Advisor: Jay Aslam.
}
}
@TechReport{Dartmouth:TR2003-455,
author = {Clara E. Lee },
title = {{Persistence and Prevalence in the Mobility of Dartmouth Wireless Network Users}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-455},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/325/TR2003-455.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/325/TR2003-455.pdf},
abstract = {
Wireless local-area networks (WLANs) are increasing in popularity. As more people
use WLANs it is important to understand how these users behave. We analyzed data
collected over three months of 2002 to measure the persistence and prevalence of
users of the Dartmouth wireless network.
We found that most of the users of Dartmouth's network have short association times
and a high rate of mobility. This observation fits with the predominantly student
population of Dartmouth College, because students do not have a fixed workplace
and are moving to and from classes all day.
}
comment = {
The data in this paper is highly suspect; see TR2003-480.
}
}
@TechReport{Dartmouth:TR2003-454,
author = {David M. Nicol and Guanhua Yan },
title = {{Discrete-Event Fluid Modeling of Background TCP Traffic}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-454},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/324/TR2003-454.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/324/TR2003-454.pdf},
abstract = {
TCP is the most widely used transport layer protocol used in the internet today.
A TCP session adapts the demands it places on the network to observations of bandwidth
availability on the network. Because TCP is adaptive, any model of its behavior
that aspires to be accurate must be influenced by other network traffic. This point
is especially important in the context of using simulation to evaluate some new
network algorithm of interest (e.g. reliable multi-cast) in an environment where
the background traffic affects---and is affected by---its behavior. We need to generate
background traffic efficiently in a way that captures the salient features of TCP,
while the reference and background traffic representations interact with each other.
This paper describes a fluid model of TCP and a switching model that has flows represented
by fluids interacting with packet-oriented flows. We describe conditions under which
a fluid model produces exactly the same behavior as a packet-oriented model, and
we quantify the performance advantages of the approach both analytically and empirically.
We observe that very significant speedups may be attained while keeping high accuracy.
}
}
@TechReport{Dartmouth:TR2003-453,
author = {Sidharth P. Nazareth },
title = {{SPADE: SPKI/SDSI for Attribute Release Policies in a Distributed Environment}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-453},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/323/TR2003-453.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/323/TR2003-453.pdf},
abstract = {
Shibboleth is a federated administrated system that supports inter-institutional
authentication and authorization for sharing of resources. SPKI/SDSI is a public
key infrastructure whose creation was motivated by the perception that X.509 is
too complex and flawed. This thesis addresses the problem of how users that are
part of a Public Key Infrastructure in a distributed computing system can effectively
specify, create, and disseminate their Attribute Release Policies for Shibboleth
using SPKI/SDSI. This thesis explores existing privacy mechanims, as well as distributed
trust management and policy based systems. My work describes the prototype for a
Trust Management Framework called SPADE (SPKI/SDSI for Attribute Release Policies
in a Distributed Environment) that I have designed, developed and implemented. The
principal result of this research has been the demonstration that SPKI/SDSI is a
viable approach for trust management and privacy policy specification, especially
for minimalistic policies in a distributed environment.
}
comment = {
M.S Thesis. Advisor: Sean Smith
}
}
@TechReport{Dartmouth:TR2003-452,
author = {Brian J. Premore },
title = {{An Analysis of Convergence Properties of the Border Gateway Protocol Using Discrete Event Simulation}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-452},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/322/TR2003-452.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/322/TR2003-452.pdf},
abstract = {
The Internet is an enormous internetwork formed by connecting tens of thousands of
independently managed computer networks. Though the Internet has no central authority
and is highly heterogeneous, a universally adopted addressing scheme---defined by
the Internet Protocol (IP)---makes interaction between the individual networks possible.
Complementing IP is the Border Gateway Protocol (BGP), which facilitates communication
between parts of the internetwork by determining paths by which data can get from
one network to any other. Just as IP is used ubiquitously as an addressing scheme,
BGP is used ubiquitously for the purpose of network-to-network routing.
Because BGP is universal, its well-being is the concern of everyone. In other words,
when BGP suffers, everyone suffers. Even when just one instance of BGP on one router
is ill-behaved, it can have global effects. Unfortunately, as the Internet has grown,
the amount of stress put on BGP has increased. For a long time, the behavior of
inter-domain routing was studied minimally and was assumed to be working just fine.
Research eventually showed, however, that routing was not actually functioning so
smoothly, and the highly dynamic nature of the Internet was taking its toll on the
routing infrastructure. This discovery prompted a closer look at the behavior of
BGP.
Though its underlying premise is a simple distributed shortest-path algorithm, the
dynamic nature of the Internet, combined with some additional constraints in the
protocol, has made analytical approaches to studying the protocol infeasible. Measurement-based
approaches have been taken, but they are difficult to implement and have minimal
leeway for allowing exploration of the protocol's behavior under different conditions.
For these reasons we have taken the approach of simulation in order to begin to
understand some of the complex ways in which BGP behaves. Simulation allows one
to explore the protocol more fully, testing it under various conditions and modifying
the protocol itself to explore the consequences of its fundamental design.
We have studied BGP behavior with respect to several parameters, some external (network
characteristics) and some internal (protocol characteristics). We show that there
is room for improvement in the protocol, in particular with respect to convergence
following changes in availability of an address in the network. The rate-limiting
mechanism of the protocol is a particular parameter of concern. Although it was
previously thought to help improve convergence, we found that in some cases it can
have drastic degrading effects. As a result of our work, we suggest ways in which
BGP could be modified in practice to reduce the instability of the protocol.
}
comment = {
This is a Ph.D. thesis. It differs from the version of the thesis which appears in
the Dartmouth College library in a couple of significant ways. First, it is single-spaced.
Figures have moved around in order to accommodate this change. Second, it includes
some corrections. The primary correction is that some bibliography entries were
reordered in order to properly alphabetize them. This has the side effect that the
numbered citations throughout the document are different in this version than in
the original version.
}
}
@TechReport{Dartmouth:TR2003-451,
author = {Chris Lentz },
title = {{802.11b Wireless Network Visualization and Radiowave Propagation Modeling}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-451},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/321/TR2003-451.pdf},
abstract = {
This paper outlines the methods of creating detailed coverage maps of 802.11b networks,
with an emphasis on minimizing the expenses and time involved. The goal of this
work is to develop and present a streamlined, reproducible approach to wireless
visualization as well as techniques for predicting coverage area before conducting
network installations.
After evaluating these coverage maps, a repeated series of field measurements will
be checked against interpolated values in order to improve techniques for extrapolation
of data for unsampled regions. If successful, these extrapolation techniques will
provide additional guidelines for, and assist modeling of, new wireless network
installations. However, this paper demonstrates that due to the microcellular structure
of indoor/outdoor 802.11b networks, accurate interpolation and propagation prediction
techniques do not exist independent of highly specific location models. In lieu
of the creation of extensive simulation environments, best practice guidelines for
municipal wireless network planning and deployment are presented.
}
comment = {
Senior thesis. Advisor: David Kotz.
}
}
@TechReport{Dartmouth:TR2003-450,
author = {Evan W. Richardson },
title = {{An Evaluation of the Impact of Models for Radio Propagation on the Simulation of 802.11b Wireless Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-450},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/320/TR2003-450.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/320/TR2003-450.pdf},
abstract = {
Working with an existing wireless network simulator, we describe the addition of
both a method for modeling arbitrary terrain, and for calculating signal attenuation
with the Irregular Terrain Model (ITM). We also investigate ITM's effects on upper
protocol layer in comparison to the Two-Ray Ground Reflection model. Upon examination,
it was found that aside from the terrain between the transmitter and receiver, ITM's
various parameters are of little significance in the computed signal attenuation.
Further, examination of the behavior of the upper protocol layers revealed that
at high traffic levels, choice of propagation model can have significant effects
on the results of the simulation.
}
comment = {
Senior Honors Thesis. Advisor: Felipe Perrone.
}
}
@TechReport{Dartmouth:TR2003-449,
author = {Lisa A. Torrey },
title = {{An Active Learning Approach to Efficiently Ranking Retrieval Engines}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-449},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/319/TR2003-449.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/319/TR2003-449.pdf},
abstract = {
Evaluating retrieval systems, such as those submitted to the annual TREC competition,
usually requires a large number of documents to be read and judged for relevance
to query topics. Test collections are far too big to be exhaustively judged, so
only a subset of documents is selected to form the judgment ``pool.'' The selection
method that TREC uses produces pools that are still quite large. Research has indicated
that it is possible to rank the retrieval systems correctly using substantially
smaller pools.
This paper introduces an active learning algorithm whose goal is to reach the correct
rankings using the smallest possible number of relevance judgments. It adds one
document to the pool at a time, always trying to select the document with the highest
information gain. Several variants of this algorithm are described, each with improvements
on the one before. Results from experiments are included for comparison with the
traditional TREC pooling method. The best version of the algorithm reliably outperforms
the traditional method, although its degree of improvement varies.
}
comment = {
Senior Honors Thesis. Advisor: Jay Aslam.
}
}
@TechReport{Dartmouth:TR2003-448,
author = {Thomas Mueller },
title = {{Billiards Adviser as a Search in a Continuous Domain with Significant Uncertainty}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-448},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/318/TR2003-448.pdf},
abstract = {
Typical search algorithms are limited to problems in which there is a certain number
of moves for any given state, and the effect of each move is well known. In order
to overcome this limitation, we consider the problem of determining the optimal
shot given the positions of balls on a billiards table. Our solution includes the
image recognition necessary to determine each ball's position, the calculation of
the optimal shot, and the presentation of that shot to the player. The focus of
the paper is on the second part - determining the angle and force with which the
player should attempt to hit the cue ball for each shot in order to sink all of
the other balls with the fewest shots. The solution to this problem is unique from
other game search algorithms in that it must take into account the infinite number
of possible shots given any configuration of balls as well as the fact that the
player is not likely to hit the ball exactly how he attempts to do so. We compare
the performance of our algorithm with one that ignores the latter fact to show that
our modifications do in fact improve performance for a search in a continuous domain
with significant uncertainty.
}
comment = {
Advisor: Zack Butler
}
}
@TechReport{Dartmouth:TR2003-446,
author = {Prasad Jayanti and Srdjan Petrovic },
title = {{Efficient and Practical Constructions of LL/SC Variables}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-446},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/317/TR2003-446.pdf},
abstract = {
Over the past decade, LL/SC have emerged as the most suitable synchronization instructions
for the design of lock-free algorithms. However, current architectures do not support
these instructions; instead, they support either CAS or RLL/RSC (e.g. POWER4, MIPS,
SPARC, IA-64). To bridge this gap, this paper presents two efficient wait-free algorithms
for implementing 64-bit LL/SC objects from 64-bit CAS or RLL/RSC objects.
Our first algorithm is practical: it has a small, constant time complexity (of
4 for LL and 5 for SC) and a space overhead of only 4 words per process. This algorithm
uses unbounded sequence numbers. For theoretical interest, we also present a more
complex bounded algorithm that still guarantees constant time complexity and O(1)
space overhead per process.
The LL/SC primitive is free of the well-known ABA problem that afflicts CAS. By
efficiently implementing LL/SC words from CAS words, this work presents an efficient
general solution to the ABA problem.
}
}
@TechReport{Dartmouth:TR2003-445,
author = {Geeta Chaudhry and Elizabeth A. Hamon and Thomas H. Cormen },
title = {{Relaxing the Problem-Size Bound for Out-of-Core Columnsort}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-445},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/316/TR2003-445.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/316/TR2003-445.pdf},
abstract = {
Previous implementations of out-of-core columnsort limit the problem size to $N leq
sqrt{(M/P)^3 / 2}$, where $N$ is the number of records to sort, $P$ is the number
of processors, and $M$ is the total number of records that the entire system can
hold in its memory (so that $M/P$ is the number of records that a single processor
can hold in its memory). We implemented two variations to out-of-core columnsort
that relax this restriction. Subblock columnsort is based on an algorithmic modification
of the underlying columnsort algorithm, and it improves the problem-size bound to
$N leq (M/P)^{5/3} / 4^{2/3}$ but at the cost of additional disk I/O@. $M$-columnsort
changes the notion of the column size in columnsort, improving the maximum problem
size to $N leq sqrt{M^3 / 2}$ but at the cost of additional computation and communication.
Experimental results on a Beowulf cluster show that both subblock columnsort and
$M$-columnsort run well but that $M$-columnsort is faster. A further advantage of
$M$-columnsort is that it handles a wider range of problem sizes than subblock columnsort.
}
}
@TechReport{Dartmouth:TR2003-444,
author = {Geeta Chaudhry and Thomas H. Cormen },
title = {{Stupid Columnsort Tricks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-444},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/315/TR2003-444.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/315/TR2003-444.pdf},
abstract = {
Leighton's columnsort algorithm sorts on an $r times s$ mesh, subject to the restrictions
that $s$ is a divisor of~$r$ and that $r geq 2s^2$ (so that the mesh is tall and
thin). We show how to mitigate both of these restrictions. One result is that the
requirement that $s$ is a divisor of~$r$ is unnecessary; columnsort sorts correctly
whether or not $s$ divides~$r$. We present two algorithms that, as long as $s$ is
a perfect square, relax the restriction that $r geq 2s^2$; both reduce the exponent
of~$s$ to~$3/2$. One algorithm requires $r geq 4s^{3/2}$ if $s$ divides~$r$ and
$r geq 6s^{3/2}$ if $s$ does not divide~$r$. The other algorithm requires $r geq
4^{3/2}$, and it requires $s$ to be a divisor of~$r$. Both algorithms have applications
in increasing the maximum problem size in out-of-core sorting programs.
}
}
@TechReport{Dartmouth:TR2003-443,
author = {John C. Marchesini and Sean W. Smith and Meiyuan Zhao },
title = {{Keyjacking: Risks of the Current Client-side Infrastructure}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-443},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/314/TR2003-443.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/314/TR2003-443.pdf},
abstract = {
In theory, PKI can provide a flexible and strong way to authenticate users in distributed
information systems. In practice, much is being invested in realizing this vision
via client-side SSL and browser-based keystores. Exploring this vision, we demonstrate
that browsers will use personal certificates to authenticate requests that the person
neither knew of nor approved (and which password-based systems would have defeated),
and we demonstrate the easy permeability of these keystores (including new attacks
on medium and high-security IE/XP keys). We suggest some countermeasures, but also
suggest that a fundamental rethinking of the trust, usage, and storage model might
result in a more effective PKI.
}
}
@TechReport{Dartmouth:TR2003-442,
author = {Alex Iliev and Sean Smith },
title = {{Privacy-enhanced credential services}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-442},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/313/TR2003-442.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/313/TR2003-442.pdf},
abstract = {
The use of credential directories in PKI and authorization systems such as Shibboleth
introduces a new privacy risk: an insider at the directory can learn much about
otherwise protected interactions by observing who makes queries, and what they ask
for. Recent advances in Practical Private Information Retrieval provide promising
countermeasures. In this paper, we extend this technology to solve this new privacy
problem, and present a design and preliminary prototype for a LDAP-based credential
service that can prevent even an insider from learning anything more than the fact
a query was made. Our preliminary performance analysis suggests that the complete
prototype may be sufficiently robust for academic enterprise settings.
}
comment = {
Submitted to the 2nd Annual PKI Research Workshop.
}
}
@TechReport{Dartmouth:TR2003-441,
author = {Yasir Ali and S. W. Smith },
title = {{Flexible and Scalable Public Key Security for SSH}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-441},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/312/TR2003-441.pdf},
abstract = {
A standard tool for secure remote access, the SSH protocol uses public-key cryptography
to establish an encrypted and integrity-protected channel with a remote server.
However, widely-deployed implementations of the protocol are vulnerable to man-in-the-middle
attacks, where an adversary substitutes her public key for the server's. This danger
particularly threatens a traveling user Bob borrowing a client machine.
Imposing a traditional X.509 PKI on all SSH servers and clients is neither flexible
nor scalable nor (in the foreseeable future) practical. Requiring extensive work
or an SSL server at Bob's site is also not practical for many users.
This paper presents our experiences designing and implementing an alternative scheme
that solves the public-key security problem in SSH without requiring such an a priori
universal trust structure or extensive sysadmin work--although it does require a
modified SSH client. (The code is available for public download.)
}
comment = {
A revised version, published as a conference paper, as follows:
Y. Ali, S.W.
Smith.
"Flexible and Scalable Public Key Security for SSH."
Public Key Infrastructure:
EuroPKI 2004, pp. 43-56,
LNCS 3093, June 2004. Springer-Verlag. DOI 10.1007/b98201.
http://dx.doi.org/10.1007/b98201
http://www.springerlink.com/site-content/h8jng6kc1rf3j97g/
}
}
@TechReport{Dartmouth:TR2003-440,
author = {David M. Nicol and Sean W. Smith and Meiyuan Zhao },
title = {{Efficient Security for BGP Route Announcements}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-440},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/311/TR2003-440.R2.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/311/TR2003-440.R2.pdf},
abstract = {
The Border Gateway Protocol (BGP) determines how Internet traffic is routed throughout
the entire world; malicious behavior by one or more BGP speakers could create serious
security issues. Since the protocol depends on a speaker honestly reporting path
information sent by previous speakers and involves a large number of independent
speakers, the Secure BGP (S-BGP) approach uses public-key cryptography to ensure
that a malicious speaker cannot fabricate this information. However, such public-key
cryptography is expensive: S-BGP requires a digital signature operation on each
announcement sent to each peer, and a linear (in the length of the path) number
of verifications on each receipt. We use simulation of a 110 AS system derived from
the Internet to evaluate the impact that the processing costs of cryptography have
on BGP convergence time. We find that under heavy load the convergence time using
ordinary S-BGP is nearly twice as large as under BGP. We examine the impact of highly
aggressive caching and pre-computation optimizations for S-BGP, and find that convergence
time is much closer to BGP. However, these optimizations may be unrealistic, and
are certainly expensive of memory. We consequently use the structure of BGP processing
to design optimizations that reduce cryptographic overhead by amortizing the cost
of private-key signatures over many messages. We call this method Signature-Amortization
(S-A). We find that S-A provides as good or better convergence times as the highly
optimized S-BGP, but without the cost and complications of caching and pre-computation.
It is possible therefore to minimize the impact route validation has on convergence,
by being careful with signatures, rather than consumptive of memory.
}
comment = {
Revision 2 released May 9, 2003. Original revision 1, of February 2003, is available
in pdf or ps.Z.
}
}
@TechReport{Dartmouth:TR2003-439,
author = {Chris J. Langmead and Bruce R. Donald },
title = {{3D-Structural Homology Detection via Unassigned Residual Dipolar Couplings}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2003-439},
year = {2003},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/310/TR2003-439.pdf},
abstract = {
Recognition of a protein's fold provides valuable information about its function.
While many sequence-based homology prediction methods exist, an important challenge
remains: two highly dissimilar sequences can have similar folds --- how can we detect
this rapidly, in the context of structural genomics? High-throughput NMR experiments,
coupled with novel algorithms for data analysis, can address this challenge. We
report an automated procedure for detecting 3D-structural homologies from sparse,
unassigned protein NMR data.
Our method identifies the 3D-structural models in a protein structural database
whose geometries best fit the unassigned experimental NMR data. It does not use
sequence information and is thus not limited by sequence homology. The method can
also be used to confirm or refute structural predictions made by other techniques
such as protein threading or sequence homology. The algorithm runs in O(pnk3)
time, where p is the number of proteins in the database, n is the number of residues
in the target protein, and k is the resolution of a rotation search. The method
requires only uniform 15N-labelling of the protein and processes unassigned 1H-15N
residual dipolar couplings, which can be acquired in a couple of hours. Our experiments
on NMR data from 5 different proteins demonstrate that the method identifies closely
related protein folds, despite low-sequence homology between the target protein
and the computed model.
}
comment = {
A revised and expanded version of this TR will appear as a refereed paper at the
IEEE Computer Society
Bioinformatics Conference , Stanford, California (August, 2003),
}
}
@TechReport{Dartmouth:TR2002-438,
author = {Valentino Crespi },
title = {{Exact formulae for the Lovasz Theta Function of sparse Circulant Graphs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-438},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/309/TR2002-438.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/309/TR2002-438.pdf},
abstract = {
The Lovasz theta function has attracted a lot of attention for its connection with
diverse issues, such as communicating without errors and computing large cliques
in graphs. Indeed this function enjoys the remarkable property of being computable
in polynomial time, despite being sandwitched between clique and chromatic number,
two well known hard to compute quantities.
In this paper I provide a closed formula for the Lovasz function of a specific class
of sparse circulant graphs thus generalizing Lovasz results on cycle graphs (circulant
graphs of degree 2).
}
}
@TechReport{Dartmouth:TR2002-437,
author = {Heng Huang and Chris Hawblitzel },
title = {{Proofs of Soundness and Strong Normalization for Linear Memory Types}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-437},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/308/TR2002-437.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/308/TR2002-437.pdf},
abstract = {
Efficient low-level systems need more control over memory than safe high-level languages
usually provide. As a result, run-time systems are typically written in unsafe languages
such as C. This report describes an abstract machine designed to give type-safe
code more control over memory. It includes complete definitions and proofs.
}
}
@TechReport{Dartmouth:TR2002-436,
author = {Robert C. Fitch },
title = {{Heterogeneous Self-Reconfiguring Robotics}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-436},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/307/TR2002-436.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/307/TR2002-436.pdf},
abstract = {
Self-reconfiguring robots are modular systems that can change shape, or "reconfigure,"
to match structure to task. They comprise many small, discrete, often identical
modules that connect together and that are minimally actuated. Global shape transformation
is achieved by composing local motions. Systems with a single module type, known
as "homogeneous" systems, gain fault tolerance, robustness and low production cost
from module interchangeability. However, we are interested in "heterogeneous" systems,
which include multiple types of modules such as those with sensors, batteries or
wheels. We believe that heterogeneous systems offer the same benefits as homogeneous
systems with the added ability to match not only structure to task, but also capability
to task.
Although significant results have been achieved in understanding homogeneous systems,
research in heterogeneous systems is challenging as key algorithmic issues remain
unexplored. We propose in this thesis to investigate questions in four main areas:
1) how to classify heterogeneous systems, 2) how to develop efficient heterogeneous
reconfiguration algorithms with desired characteristics, 3) how to characterize
the complexity of key algorithmic problems, and 4) how to apply these heterogeneous
algorithms to perform useful new tasks in simulation and in the physical world.
Our goal is to develop an algorithmic basis for heterogeneous systems. This has
theoretical significance in that it addresses a major open problem in the field,
and practical significance in providing self-reconfiguring robots with increased
capabilities.
}
}
@TechReport{Dartmouth:TR2002-435,
author = {Qun Li and Michael De Rosa and Daniela Rus },
title = {{Distributed Algorithms for Guiding Navigation across a Sensor Network}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-435},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/306/TR2002-435.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/306/TR2002-435.pdf},
abstract = {
We develop distributed algorithms for self-reconfiguring sensor networks that respond
to directing a target through a region. The sensor network models the danger levels
sensed across its area and has the ability to adapt to changes. It represents the
dangerous areas as obstacles. A protocol that combines the artificial potential
field of the sensors with the goal location for the moving object guides the object
incrementally across the network to the goal, while maintaining the safest distance
to the danger areas. We report on hardware experiments using a physical sensor network
consisting of Mote sensors.
}
}
@TechReport{Dartmouth:TR2002-434,
author = {Ryan H. Lilien and Hany Farid and Bruce R. Donald },
title = {{Probabilistic Disease Classification of Expression-Dependent Proteomic Data from Mass Spectrometry of Human Serum}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-434},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/305/TR2002-434.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/305/TR2002-434.pdf},
abstract = {
We have developed an algorithm called Q5 for probabilistic classification of healthy
vs. disease whole serum samples using mass spectrometry. The algorithm employs Principal
Components Analysis (PCA) followed by Linear Discriminant Analysis (LDA) on whole
spectrum Surface-Enhanced Laser Desorption/Ionization Time of Flight (SELDI-TOF)
Mass Spectrometry (MS) data, and is demonstrated on four real datasets from complete,
complex SELDI spectra of human blood serum.
Q5 is a closed-form, exact solution to the problem of classification of complete
mass spectra of a complex protein mixture. Q5 employs a novel probabilistic classification
algorithm built upon a dimension-reduced linear discriminant analysis. Our solution
is computationally efficient; it is non-iterative and computes the optimal linear
discriminant using closed-form equations. The optimal discriminant is computed and
verified for datasets of complete, complex SELDI spectra of human blood serum. Replicate
experiments of different training/testing splits of each dataset are employed to
verify robustness of the algorithm. The probabilistic classification method achieves
excellent performance. We achieve sensitivity, specificity, and positive predictive
values above 97% on three ovarian cancer datasets and one prostate cancer dataset.
The Q5 method outperforms previous full-spectrum complex sample spectral classification
techniques, and can provide clues as to the molecular identities of differentially-expressed
proteins and peptides.
}
comment = {
To appear in Journal of Computational Biology (2003).
}
}
@TechReport{Dartmouth:TR2002-433,
author = {Ron Oldfield and David Kotz },
title = {{Using the Emulab network testbed to evaluate the Armada I/O framework for computational grids}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-433},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/304/TR2002-433.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/304/TR2002-433.pdf},
abstract = {
This short report describes our experiences using the Emulab network testbed at the
University of Utah to test performance of the Armada framework for parallel I/O
on computational grids.
}
}
@TechReport{Dartmouth:TR2002-432,
author = {David Kotz and Kobby Essien },
title = {{Analysis of a Campus-wide Wireless Network}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-432},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/303/TR2002-432.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/303/TR2002-432.pdf},
abstract = {
Understanding usage patterns in wireless local-area networks (WLANs) is critical
for those who develop, deploy, and manage WLAN technology, as well as those who
develop systems and application software for wireless networks. This paper presents
results from the largest and most comprehensive trace of network activity in a large,
production wireless LAN. For eleven weeks we traced the activity of nearly two thousand
users drawn from a general campus population, using a campus-wide network of 476
access points spread over 161 buildings. Our study expands on those done by Tang
and Baker, with a significantly larger and broader population.
We found that residential traffic dominated all other traffic, particularly in residences
populated by newer students; students are increasingly choosing a wireless laptop
as their primary computer. Although web protocols were the single largest component
of traffic volume, network backup and file sharing contributed an unexpectedly large
amount to the traffic. Although there was some roaming within a network session,
we were surprised by the number of situations in which cards roamed excessively,
unable to settle on one access point. Cross-subnet roams were an especial problem,
because they broke IP connections, indicating the need for solutions that avoid
or accommodate such roams.
}
comment = {
This paper is a revision of the MOBICOM '02 paper by the same title. The only difference
is the correction of Figures 27-28 and the associated text. This report supplants
TR2002-423.
}
}
@TechReport{Dartmouth:TR2002-431,
author = {Kobby Essien },
title = {{Analysis of Protein Sequences Using Time Frequency and Kolmogorov-Smirnov Methods}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-431},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/302/TR2002-431.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/302/TR2002-431.pdf},
abstract = {
The plethora of genomic data currently available has resulted in a search for new
algorithms and analysis techniques to interpret genomic data. In this two-fold study
we explore techniques for locating critical amino acid residues in protein sequences
and for estimating the similarity between proteins. We demonstrate the use of the
Short-Time Fourier Transform and the Continuous Wavelet Transform together with
amino acid hydrophobicity in locating important amino acid domains in proteins and
also show that the Kolmogorov-Smirnov statistic can be used as a metric of protein
similarity.
}
comment = {
Senior Honors Thesis. Advisor: Metin Akay.
}
}
@TechReport{Dartmouth:TR2002-430,
author = {Eileen Zishuang Ye },
title = {{Building Trusted Paths for Web Browsers}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-430},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/301/TR2002-430.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/301/TR2002-430.pdf},
abstract = {
The communication between the Web browser and the human user is one component of
the server-client channel. It is not the user but the browser that receives all
server information and establishes the secure connection. The browser's user interface
signals, such as SSL lock, https protocol header et al., indicate whether the browser-server
communication at the current moment is secure. Those user interface signals indicating
the security status of browser should be clearly and correctly understood by the
user.
A survey of modern Web browsers shows the information provided by current browsers
is insufficient for users to make trust judgment. Our Web spoofing work further
proved that the browser status information is not reliable either.
We discuss the criteria for and how to build the trusted paths between a browser
and a human user. We present an open source implementation of one of the designs--synchronized
random dynamic (SRD) boundary, based on Modified Mozilla source code, together with
its usability study results.
}
}
@TechReport{Dartmouth:TR2002-429,
author = {A. Abram White },
title = {{XSLT and XQuery as Operator Languages}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-429},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/300/TR2002-429.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/300/TR2002-429.pdf},
abstract = {
Ubiquitous computing promises to integrate computers into our physical environment,
surrounding us with applications that are able to adapt to our dynamics. Solar is
a software infrastructure designed to deliver contextual information to these applications.
Solar represents context data as events, and uses small programs called operators
to filter, merge, aggregate, or transform event streams. This paper explores the
possibility of using XSLT and XQuery to build language-neutral Solar operators.
}
comment = {
See also TR2002-427.
}
}
@TechReport{Dartmouth:TR2002-428,
author = {Sebastien M. Lahaie },
title = {{Information-theoretic Bounds on the Training and Testing Error of Boosting}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-428},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/299/TR2002-428.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/299/TR2002-428.pdf},
abstract = {
Boosting is a means of using weak learners as subroutines to produce a strong learner
with markedly better accuracy. Recent results showing the connection between logistic
regression and boosting provide the foundation for an information-theoretic analysis
of boosting. We describe the analogy between boosting and gambling, which allows
us to derive a new upper bound on training error. This upper bound explicitly describes
the effect of noisy data on training error. We also use information-theoretic techniques
to derive an alternative upper-bound on testing error which is independent of the
size of the weak-learner space.
}
}
@TechReport{Dartmouth:TR2002-427,
author = {A. Abram White },
title = {{Performance and Interoperability In Solar}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-427},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/298/TR2002-427.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/298/TR2002-427.pdf},
abstract = {
Ubiquitous computing promises to integrate computers into our physical environment,
surrounding us with applications that are able to adapt to our dynamics. Solar is
a software infrastructure designed to deliver contextual information to these applications.
To serve the large number and wide variety of context-aware devices envisioned by
ubiquitous computing, Solar must exhibit both high performance and the ability to
interoperate with many computing platforms. We created a testing framework to measure
the performance of distributed systems such as Solar, as well as a pluggable data-transfer
mechanism to support the dissemination of information to heterogeneous applications.
This paper explores the testing framework developed, analyzes its findings concerning
the performance of the current Solar prototype, presents several optimizations to
Solar and their effects, and finally discusses the design of the pluggable data-transfer
mechanism.
}
comment = {
Senior Honors Thesis. Advisor: David Kotz. See also TR2002-429.
}
}
@TechReport{Dartmouth:TR2002-426,
author = {Christopher P. Masone },
title = {{Role Definition Language (RDL): A Language to Describe Context-Aware Roles}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-426},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/297/TR2002-426.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/297/TR2002-426.pdf},
abstract = {
As wireless networks become more prevalent, a widening array of computational resources
becomes available to the mobile user. Since not all users should have unrestricted
access to these resources, a method of access control must be devised. In a context-aware
environment, context information can be used to supplement more conventional password-based
access control systems. We believe the best way to achieve this is through the use
of Context-Aware Role-Based Access Control, a model in which permissions are assigned
to entities called roles, each principal is a member of one or more roles, and a
role's membership is determined using context information. We designed and implemented
RDL (Role-Definition Language), a simple, expressive and somewhat extensible programming
language to facilitate the description of roles in terms of context information.
}
comment = {
Senior Honors Thesis. Advisor: David Kotz.
}
}
@TechReport{Dartmouth:TR2002-425,
author = {Marco A. Barreno },
title = {{The Future of Cryptography Under Quantum Computers}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-425},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/296/TR2002-425.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/296/TR2002-425.pdf},
abstract = {
Cryptography is an ancient art that has passed through many paradigms, from simple
letter substitutions to polyalphabetic substitutions to rotor machines to digital
encryption to public-key cryptosystems. With the possible advent of quantum computers
and the strange behaviors they exhibit, a new paradigm shift in cryptography may
be on the horizon. Quantum computers could hold the potential to render most modern
encryption useless against a quantum-enabled adversary. The aim of this thesis is
to characterize this convergence of cryptography and quantum computation.
We provide definitions for cryptographic primitives that frame them in general terms
with respect to complexity. We explore the various possible relationships between
BQP, the primary quantum complexity class, and more familiar classes, and we analyze
the possible implications for cryptography.
}
comment = {
This paper was written as a senior honors thesis with advisor Sean W. Smith.
}
}
@TechReport{Dartmouth:TR2002-424,
author = {Mark H. Montague },
title = {{Metasearch: Data Fusion for Document Retrieval}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-424},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/295/TR2002-424.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/295/TR2002-424.pdf},
abstract = {
The metasearch problem is to optimally merge the ranked lists output by an arbitrary
number of search systems into one ranked list. In this work:
(1) We show that metasearch improves upon not just the raw performance of the input
search engines, but also upon the consistency of the input search engines from query
to query.
(2) We experimentally prove that simply weighting input systems by their average
performance can dramatically improve fusion results.
(3) We show that score normalization is an important component of a metasearch
engine, and that dependence upon statistical outliers appears to be the problem
with the standard technique.
(4) We propose a Bayesian model for metasearch that outperforms the best input
system on average and has performance competetive with standard techniques.
(5) We introduce the use of Social Choice Theory to the metasearch problem, modeling
metasearch as a democratic election. We adapt a positional voting algorithm, the
Borda Count, to create a metasearch algorithm, acheiving reasonable performance.
(6) We propose a metasearch model adapted from a majoritarian voting procedure,
the Condorcet algorithm. The resulting algorithm is the best performing algorithm
in a number of situations.
(7) We propose three upper bounds for the problem, each bounding a different class
of algorithms.
We present experimental results for each algorithm using two types of experiments
on each of four data sets.
}
comment = {
Ph.D dissertation.
}
}
@TechReport{Dartmouth:TR2002-423,
author = {David Kotz and Kobby Essien },
title = {{Characterizing Usage of a Campus-wide Wireless Network}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-423},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/294/TR2002-423.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/294/TR2002-423.pdf},
abstract = {
Wireless local-area networks (WLANs) are increasingly common, but little is known
about how they are used. A clear understanding of usage patterns in real WLANs is
critical information to those who develop, deploy, and manage WLAN technology, as
well as those who develop systems and application software for wireless networks.
This paper presents results from the largest and most comprehensive trace of network
activity in a large, production wireless LAN. For eleven weeks we traced the activity
of nearly two thousand users drawn from a general campus population, using a campus-wide
network of 476 access points spread over 161 buildings. Our study expands on those
done by Tang and Baker, with a significantly larger and broader population.
We found that residential traffic dominated all other traffic, particularly in
residences populated by newer students; students are increasingly choosing a wireless
laptop as their primary computer. Although web protocols were the single largest
component of traffic volume, network backup and file sharing contributed an unexpectedly
large amount to the traffic. Although there was some roaming within a network session,
we were surprised by the number of situations in which cards roamed excessively,
unable to settle on one access point. Cross-subnet roams were an especial problem,
because they broke IP connections, indicating the need for solutions that avoid
or accommodate such roams.
}
comment = {
A major revision of this paper appeared in Mobicom 2002. The Mobicom paper contained
two erroneous figures, however; another report, TR2002-432, is the final corrected
version.
}
}
@TechReport{Dartmouth:TR2002-422,
author = {Kazuhiro Minami and David Kotz },
title = {{Controlling access to pervasive information in the ``Solar'' system}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-422},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/293/TR2002-422.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/293/TR2002-422.pdf},
abstract = {
Pervasive-computing infrastructures necessarily collect a lot of context information
to disseminate to their context-aware applications. Due to the personal or proprietary
nature of much of this context information, however, the infrastructure must limit
access to context information to authorized persons. In this paper we propose a
new access-control mechanism for event-based context-distribution infrastructures.
The core of our approach is based on a conservative information-flow model of access
control, but users may express discretionary relaxation of the resulting access-control
list (ACL) by specifying relaxation functions. This combination of automatic ACL
derivation and user-specified ACL relaxation allows access control to be determined
and enforced in a decentralized, distributed system with no central administrator
or central policy maker. It also allows users to express their personal balance
between functionality and privacy. Finally, our infrastructure allows access-control
policies to depend on context-sensitive roles, allowing great flexibility.
We describe our approach in terms of a specific context-dissemination framework,
the Solar system, although the same principles would apply to systems with similar
properties.
}
}
@TechReport{Dartmouth:TR2002-421,
author = {Guanling Chen and David Kotz },
title = {{Solar: A pervasive-computing infrastructure for context-aware mobile applications}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-421},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/292/TR2002-421.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/292/TR2002-421.pdf},
abstract = {
Emerging pervasive computing technologies transform the way we live and work by embedding
computation in our surrounding environment. To avoid increasing complexity, and
allow the user to concentrate on her tasks, applications must automatically adapt
to their changing emph{context}, the physical and computational environment in which
they run. To support these ``context-aware'' applications we propose a graph-based
abstraction for collecting, aggregating, and disseminating context information.
The abstraction models context information as emph{events}, which are produced by
emph{sources}, flow through a directed acyclic graph of event-processing emph{operators},
and are delivered to subscribing applications. Applications describe their desired
event stream as a tree of operators that aggregate low-level context information
published by existing sources into the high-level context information needed by
the application. The emph{operator graph/} is thus the dynamic combination of all
applications' subscription trees. In this paper, we motivate our graph abstraction
by discussing several applications under development, sketch the architecture of
our system (``Solar'') that implements our abstraction, report some early experimental
results from the prototype, and outline issues for future research.
}
}
@TechReport{Dartmouth:TR2002-420,
author = {Guanling Chen and David Kotz },
title = {{Context Aggregation and Dissemination in Ubiquitous Computing Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-420},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/291/TR2002-420.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/291/TR2002-420.pdf},
abstract = {
Many ``ubiquitous computing'' applications need a constant flow of information about
their environment to be able to adapt to their changing context. To support these
``context-aware'' applications we propose a graph-based abstraction for collecting,
aggregating, and disseminating context information. The abstraction models context
information as events, produced by sources and flowing through a directed acyclic
graph of event-processing operators and delivered to subscribing applications. Applications
describe their desired event stream as a tree of operators that aggregate low-level
context information published by existing sources into the high-level context information
needed by the application. The operator graph is thus the dynamic combination of
all applications' subscription trees.
In this paper, we motivate and describe our graph abstraction, and discuss a variety
of critical design issues. We also sketch our Solar system, an implementation that
represents one point in the design space for our graph abstraction.
}
comment = {
To appear in WMCSA 2002.
}
}
@TechReport{Dartmouth:TR2002-419,
author = {Dennis M. Healy and Daniel N. Rockmore and Peter J. Kostelec and Sean S. B. Moore },
title = {{FFTs for the 2-Sphere - Improvements and Variations}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-419},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/290/TR2002-419.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/290/TR2002-419.pdf},
abstract = {
Earlier work by Driscoll and Healy has produced an efficient algorithm for computing
the Fourier transform of band-limited functions on the 2-sphere. In this paper we
present a reformulation and variation of the original algorithm which results in
a greatly improved inverse transform, and consequent improved convolution algorithm
for such functions. All require at most $O(Nlog^2 N)$ operations where $N$ is the
number of sample points. We also address implementation considerations and give
heuristics for allowing reliable and computationally efficient floating point implementations
of slightly modified algorithms.
These claims are supported by extensive numerical experiments from our implementation
in C on DEC, HP, SGI and Linux Pentium platforms. These results indicate that variations
of the algorithm are both reliable and efficient for a large range of useful problem
sizes. Performance appears to be architecture-dependent. The paper concludes with
a brief discussion of a few potential applications.
}
comment = {
Preliminary versions of some of these results have appeared in the Dartmouth College
Department of Computer Science Technical Report PCS-TR94-222 and ``An FFT for the
2-sphere and Applications'', Proc. of ICASSP-96, Volume 3, pp. 1323--1326.
}
}
@TechReport{Dartmouth:TR2002-418,
author = {Eileen Ye and Sean Smith },
title = {{Trusted Paths for Browsers: An Open-Source Solution to Web Spoofing}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-418},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/289/TR2002-418.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/289/TR2002-418.pdf},
abstract = {
The security of the vast majority of ``secure'' Web services rests on SSL server
PKI. However, this PKI doesn't work if the the adversary can trick the browser into
appearing to tell the user the wrong thing about the certificates and cryptography.
The seminal web spoofing work of Felten et al demonstrated the potential, in 1996,
for malicious servers to impersonate honest servers. Our recent follow-up work explicitly
shows how malicious servers can still do this---and can also forge the existence
of an SSL session and the contents of the alleged server certificate.
This paper reports the results of our work to systematically defend against Web
spoofing, by creating a trusted path from the browser to the user. Starting with
the Mozilla source, we have implemented techniques that protect a wide variety of
browser-user communications, that require little participation by the user and minimal
disruption of the displayed server content. We have prepared shell scripts that
install these modifications on the Mozilla source, to enable others to replicate
this work.
In on-going work, we are cleaning up and fine-tuning our code. In future work,
we hope to examine more deeply the role of user interfaces in enabling users to
make effective trust judgments.
}
}
@TechReport{Dartmouth:TR2002-417,
author = {Eileen Ye and Yougu Yuan and Sean Smith },
title = {{Web Spoofing Revisited: SSL and Beyond}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-417},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/288/TR2002-417.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/288/TR2002-417.pdf},
abstract = {
Can users believe what their browsers tell them? Even sophisticated Web users decide
whether or not to trust a server based on browser cues such as location bar information,
SSL icons, SSL warnings, certificate information, and response time. In their seminal
work on Web spoofing, Felten et al showed how, in 1996, a malicious server could
forge some of these cues. However, this work used genuine SSL sessions, and Web
technology has evolved much since 1996.
The Web has since become the pre-eminent medium for electronic service delivery
to remote users, and the security of many commerce, government, and academic network
applications critically rests on the assumption that users can authenticate the
servers with which they interact. This situation raises the question: is the browser-user
communication model today secure enough to warrant this assumption?
In this paper, we answer this question by systematically showing how a malicious
server can forge every one of the above cues. Our work extends the prior results
by examining contemporary browsers, and by forging all of the SSL information a
client sees, including the very existence of an SSL session (thus providing a cautionary
tale about the security of one of the most common applications of PKI). We have
made these techniques available for public demonstration, because anything less
than working code would not convincingly answer the question. We also discuss implications
and potential countermeasures, both short-term and long-term.
}
comment = {
This TR supercedes TR2001-409.
}
}
@TechReport{Dartmouth:TR2002-416,
author = {John C. Marchesini and Sean W. Smith },
title = {{Virtual Hierarchies - An Architecture for Building and Maintaining Efficient and Resilient Trust Chains.}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-416},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/287/TR2002-416.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/287/TR2002-416.pdf},
abstract = {
In Public Key Infrastructure (PKI), the simple, monopolistic CA model works fine
until we consider the real world. Then, issues such as scalability and mutually
suspicious organizations create the need for a multiplicity of CAs, which immediately
introduces the problem of how to organize them to balance resilience to compromise
against efficiency of path discovery.
However, security has given us tools such as secure coprocessing, secret splitting,
secret sharing, and threshold cryptography for securely carrying out computations
among multiple trust domains; distributed computing has given us peer-to-peer networking,
for creating self-organizing distributed systems.
In this paper, we use these latter tools to address the former problem by overlaying
a virtual hierarchy on a mesh architecture of peer CAs, and achieving both resilience
and efficiency.
}
}
@TechReport{Dartmouth:TR2002-415,
author = {David Kotz and Robert S. Gray and Daniela Rus },
title = {{Future Directions for Mobile-Agent Research}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-415},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/286/TR2002-415.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/286/TR2002-415.pdf},
abstract = {
During a discussion in September 2000 the authors examined the future of research
on mobile agents and mobile code. (A mobile agent is a running program that can
move from host to host in network at times and to places of its own choosing.) In
this paper we summarize and reflect on that discussion. It became clear that the
field should shift its emphasis toward mobile code, in all its forms, rather than
to continue its narrow focus on mobile agents. Furthermore, we encourage the development
of modular components, so that application designers may take advantage of code
mobility without needing to rewrite their application to fit in a monolithic mobile-agent
system. There are many potential applications that may productively use mobile code,
but there is no ``killer application'' for mobile agents. Finally, we note that
although security is an important and challenging problem, there are many applications
and environments with security requirements well within the capability of existing
mobile-code and mobile-agent frameworks.
}
}
@TechReport{Dartmouth:TR2002-414,
author = {Valentino Crespi and George Cybenko and Massimo Santini and Daniela Rus },
title = {{Decentralized Control for Coordinated flow of Multi-Agent Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2002-414},
year = {2002},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/285/TR2002-414.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/285/TR2002-414.pdf},
abstract = {
This paper describes a distributed algorithm for coordinating the flow of a mass
of vehicles approaching a highway exit or a tollbooth. We provide the problem formulation,
a general methodology for distributed control and an instantiation of this methodology
to the coordinated flow problem. We analyze our algorithm and provide experimental
data.
}
}
@TechReport{Dartmouth:TR2001-413,
author = {Senthil Periaswamy and Hany Farid },
title = {{Differential Elastic Image Registration}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-413},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/284/TR2001-413.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/284/TR2001-413.pdf},
abstract = {
We have applied techniques from differential motion estimation to the problem of
automatic elastic registration of medical images. This method models the mapping
between images as a locally affine but globally smooth warp. The mapping also explicitly
accounts for variations in image intensities. This approach is simple and highly
effective across a broad range of medical images. We show the efficacy of this approach
on several synthetic and clinical images.
}
}
@TechReport{Dartmouth:TR2001-412,
author = {Hany Farid },
title = {{Detecting Steganographic Messages in Digital Images}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-412},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/283/TR2001-412.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/283/TR2001-412.pdf},
abstract = {
Techniques and applications for information hiding have become increasingly more
sophisticated and widespread. With high-resolution digital images as carriers, detecting
the presence of hidden messages has also become considerably more difficult. It
is sometimes possible, nevertheless, to detect (but not necessarily decipher) the
presence of embedded messages. The basic approach taken here works by finding predictable
higher-order statistics of ``natural'' images within a multi-scale decomposition,
and then showing that embedded messages alter these statistics.
}
}
@TechReport{Dartmouth:TR2001-411,
author = {Arne Grimstrup and Robert S. Gray and David Kotz and Thomas Cowin and Greg Hill and Niranjan Suri and Daria Chacon and Martin Hofmann },
title = {{Write Once, Move Anywhere: Toward Dynamic Interoperability of Mobile Agent Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-411},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/282/TR2001-411.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/282/TR2001-411.pdf},
abstract = {
Mobile agents are an increasingly popular paradigm, and in recent years there has
been a proliferation of mobile-agent systems. These systems are, however, largely
incompatible with each other. In particular, agents cannot migrate to a host that
runs a different mobile-agent system. Prior approaches to interoperability have
tried to force agents to use a common API, and so far none have succeeded. Our goal,
summarized in the catch phrase ``Write Once, Move Anywhere,'' led to our efforts
to develop mechanisms that support dynamic runtime interoperability of mobile-agent
systems. This paper describes the Grid Mobile-Agent System, which allows agents
to migrate to different mobile-agent systems.
}
comment = {
Revised July 25, 2001.
}
}
@TechReport{Dartmouth:TR2001-410,
author = {Shan Jiang and Sean Smith and Kazuhiro Minami },
title = {{Securing Web Servers against Insider Attack}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-410},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/281/TR2001-410.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/281/TR2001-410.pdf},
abstract = {
Too often, ``security of Web transactions'' reduces to ``encryption of the channel''---and
neglects to address what happens at the server on the other end. This oversight
forces clients to trust the good intentions and competence of the server operator---but
gives clients no basis for that trust. Furthermore, despite academic and industrial
research in secure coprocessing, many in the computer science community still regard
``secure hardware'' as a synonym for ``cryptographic accelerator.' This oversight
neglects the real potential of COTS secure coprocessing technology to establish
trusted islands of computation in hostile environments---such as at web servers
with risk of insider attack.
In this paper, we apply secure coprocessing and cryptography to solve this real
problem in Web technology. We present a vision: using secure coprocessors to establish
trusted co-servers at Web servers and moving sensitive computations inside these
co-servers. We present a prototype implementation of this vision that scales to
realistic workloads. Finally, we validate this approach by building a simple E-voting
application on top of our prototype.
From our experience, we conclude that this approach provides a practical and effective
way to enhance the security of Web servers against insider attack.
}
}
@TechReport{Dartmouth:TR2001-409,
author = {Yougu Yuan and Eileen Zishuang Ye and Sean W. Smith },
title = {{Web Spoofing 2001}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-409},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/280/TR2001-409.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/280/TR2001-409.pdf},
abstract = {
The Web is currently the pre-eminent medium for electronic service delivery to remote
users. As a consequence, authentication of servers is more important than ever.
Even sophisticated users base their decision whether or not to trust a site on browser
cues---such as location bar information, SSL icons, SSL warnings, certificate information,
response time, etc.
In their seminal work on web spoofing, Felten et al showed how a malicious server
could forge some of these cues---but using approaches that are no longer reproducible.
However, subsequent evolution of Web tools has not only patched security holes---it
has also added new technology to make pages more interactive and vivid. In this
paper, we explore the feasibility of web spoofing using this new technology---and
we show how, in many cases, every one of the above cues can be forged.
In particular, we show how a malicious server can forge all the SSL information
a client sees---thus providing a cautionary tale about the security of one of the
most common applications of PKI.
We stress that these techniques have been implemented, and are available for public
demonstration.
}
}
@TechReport{Dartmouth:TR2001-408,
author = {Jonathan L. Bredin },
title = {{Market-based Control of Mobile-agent Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-408},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/279/TR2001-408.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/279/TR2001-408.pdf},
abstract = {
Modern distributed systems scatter sensors, storage, and computation throughout the
environment. Ideally these devices communicate and share resources, but there is
seldom motivation for a device's owner to yield control to another user. We establish
markets for computational resources to motivate principals to share resources with
arbitrary users, to enforce priority in distributed systems, to provide flexible
and rational limitations on the potential of an application, and to provide a lightweight
structure to balance the workload over time and between devices. As proof of concept,
we implement a structure software agents can use to discover and negotiate access
to networked resources. The structure separates discovery, authentication, and consumption
enforcement as separate orthogonal issues to give system designers flexibility.
Mobile agents represent informational and computational flow. We develop mechanisms
that distributively allocate computation among mobile agents in two settings. The
first models a situation where users collectively own networked computing resources
and require priority enforcement. We extend the allocation mechanism to allow resource
reservation to mitigate utility volatility. The second, more general model relaxes
the ownership assumption. We apply our computational market to an open setting where
a principal's chief concern is revenue maximization. Our simulations compare the
performance of market-based allocation policies to traditional policies and relate
the cost of ownership and consumption separation. We observe that our markets effectively
prioritize applications' performance, can operate under uncertainty and network
delay, provide metrics to balance network load, and allow measurement of market-participation
risk versus reservation-based computation. In addition to allocation problems,
we investigate resource selection to optimize execution time. The problem is NP-complete
if the costs and latencies are constant. Both metrics' dependence on the chosen
set complicates matters. We study how a greedy approach, a novel heuristic, and
a shortest-constrained-path strategy perform in mobile-agent applications. Market-based
computational-resource allocation fertilizes applications where previously there
was a dearth of motive for or means of cooperation. The rationale behind mobile-agent
performance optimization is also useful for resource allocation in general distributed
systems where an application has a sequence of dependent tasks or when data collection
is expensive.
}
comment = {
A Ph.D thesis from the Department of Computer Science, Dartmouth College.
}
}
@TechReport{Dartmouth:TR2001-407,
author = {Michael G. Khankin },
title = {{TCP/IP Implementation within the Dartmouth Scalable Simulation Framework}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-407},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/278/TR2001-407.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/278/TR2001-407.pdf},
abstract = {
This paper discusses TCP/IP networking, and in particular, the DaSSF implementation
of TCP/IP. The paper reviews the protocols, outlines the implementation design,
and demonstrates some tests. In addition, some performance and memory usage analysis
is performed. We find DaSSF TCP/IP to be a viable option to the existing SSF. DaSSF
TCP/IP is faster and uses less memory so we can simulate larger, more complex, models.
}
comment = {
Senior Honors Thesis. Advisor: David M. Nicol
}
}
@TechReport{Dartmouth:TR2001-406,
author = {Jeremy I. Robin },
title = {{Fastab: Solving the Pitch to Notation Problem}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-406},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/277/TR2001-406.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/277/TR2001-406.pdf},
abstract = {
I have always been frustrated with the length of time necessary to notate a piece
of music. Computers have simplified so many other aspects of our lives, it seems
that they should be able to simplify this task as well. In fact, there are already
two distinct ways that engineers have attempted to attack this problem. The first
analyzes the waveform generated by microphone input and relies on Fourier Analysis
and other similar methods. The other examines the analog signal generated by a electric
guitar-like pickup placed beneath the strings. The method used by Fastab relies
much less on the musical properties of an instrument. Instead, Fastab records where
and when the fingers and pick contact the instrument using digital electronics and
microprocessor technology. Fastab provides a solution to the pitch to notation problem
which is cheaper and more accurate than any other device available today.
}
comment = {
Senior Honors Thesis. Advisor: Scot Drysdale
}
}
@TechReport{Dartmouth:TR2001-405,
author = {Mehmet Iyigun },
title = {{DaSSFNet: An Extension to DaSSF for High-Performance Network Modeling}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-405},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/276/TR2001-405.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/276/TR2001-405.pdf},
abstract = {
Scalable Simulation Framework (SSF) is a discrete-event simulation framework providing
a unified programming interface geared towards network simulation. Dartmouth SSF
(DaSSF) is a C++ implementation of SSF, designed for simulating very large-scale
multi-protocol communication networks. As of the latest release, DaSSF lacks many
features present in SSF and this prevents it from achieving mainstream use. To alleviate
this shortcoming we designed and implemented DaSSFNet which extends DaSSF to the
levels of functionality found in SSF. In this paper, we show that DaSSFNet and SSFNet
are identical in operation given the same input. We also show that DaSSFNet is about
twice as fast and has one third the memory consumption of SSFNet when simulating
identical networks. Therefore, we argue, that the DaSSF simulation package with
DaSSFNet now offers a viable alternative to SSF in high-performance network simulation.
}
comment = {
Senior Honors Thesis. Advisor: David M. Nicol
}
}
@TechReport{Dartmouth:TR2001-404,
author = {Eric Kidd },
title = {{Efficient Compression of Generic Function Dispatch Tables}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-404},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/275/TR2001-404.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/275/TR2001-404.pdf},
abstract = {
A generic function is similar to an overloaded operator, but provides a way to select
an appropriate behavior at run-time instead of compile-time. Dujardin and colleagues
have proposed an algorithm for building and compressing generic function dispatch
tables.
We present several modifications to their algorithm, including an improvement to
Pseudo-Closest-Poles and two new algorithms for compressing pole tables. The two
new compression algorithms are simple and fast, and one produces smaller output
than the original.
}
comment = {
Senior Honors Thesis. Advisor: Chris Hawblitzel.
}
}
@TechReport{Dartmouth:TR2001-403,
author = {Aidan S. Marcuss },
title = {{EcomRISK.org : A site to classify and organize the risks of performing business on the Internet}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-403},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/274/TR2001-403.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/274/TR2001-403.pdf},
abstract = {
As the use of the Internet and other computer networks to transact business grows,
there is an ever increasing need for those taking part in those transactions to
understand the risks of doing so. While there are many web sites that have created
valuable databases of specific vulnerabilities for certain types of hardware and
software, there is a lack of focus on attempting to analyze the interaction of businesses,
their systems, computer networks, and their customers and the risks that are created
by either intended or unattended interactions. EcomRISK.org is a web site that presents
a clear taxonomy to classify these risks and provides other features to aid in the
general discussion of e-commerce risk. The site, and the taxonomy at the center
of it, creates a database of these incidents so they can be clearly searched. This
paper discusses the creation of EcomRISK.org, from vision to birth.
}
comment = {
Senior Honors Thesis. Advisor: Fillia Makedon.
}
}
@TechReport{Dartmouth:TR2001-402,
author = {Jeremy T. Fineman },
title = {{Optimizing the Dimensional Method for Performing Multidimensional, Multiprocessor, Out-of-Core FFTs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-402},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/273/TR2001-402.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/273/TR2001-402.pdf},
abstract = {
We present an improved version of the Dimensional Method for computing multidimensional
Fast Fourier Transforms (FFTs) on a multiprocessor system when the data consist
of too many records to fit into memory. Data are spread across parallel disks and
processed in sections. We use the Parallel Disk Model for analysis.
The simple Dimensional Method performs the 1-dimensional FFTs for each dimension
in term. Between each dimension, an out-of-core permutation is used to rearrange
the data to contiguous locations. The improved Dimensional Method processes multiple
dimensions at a time.
We show that determining an optimal sequence and groupings of dimensions is NP-complete.
We then analyze the effects of two modifications to the Dimensional Method independently:
processing multiple dimensions at one time, and processing single dimensions in
a different order.
Finally, we show a lower bound on the I/O complexity of the Dimensional Method
and present an algorithm that is approximately asymptotically optimal.
}
comment = {
Senior Honors Thesis. Advisor: Tom Cormen.
}
}
@TechReport{Dartmouth:TR2001-401,
author = {Sean W. Smith },
title = {{Outbound Authentication for Programmable Secure Coprocessors}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-401},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/272/TR2001-401.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/272/TR2001-401.pdf},
abstract = {
A programmable secure coprocessor platform can help solve many security problems
in distributed computing. These solutions usually require that coprocessor applications
be able to participate as full-fledged parties in distributed cryptographic protocols.
Thus, to fully enable these solutions, a generic platform must not only provide
programmability, maintenance, and configuration in the hostile field---it must also
provide outbound authentication for the entities that result. A particular application
on a particular untampered device must be able to prove who it is to a party on
the other side of the Internet.
To be effective, a secure outbound authentication service must closely mesh with
the overall security architecture. Our initial architecture only sketched a rough
design for this service, and did not complete it. This paper presents our research
and development experience in refining and implementing this design, to provide
PKI-based outbound authentication for the IBM 4758 Model 2 secure coprocessor platform.
}
}
@TechReport{Dartmouth:TR2001-400,
author = {Alex Iliev },
title = {{An Armored Data Vault}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-400},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/271/TR2001-400.pdf},
abstract = {
We consider the problem of secure long-term archiving of network traffic, an instance
of the problem of storing data securely. We approach the problem using secure hardware,
which enables the enforcement of flexible access policy. The policy cannot be circumvented
by anyone, even insiders, and so we are assured that access to the data is as originally
intended. The policy can be expressed as any feasible computation, as it will be
checked inside the secure hardware without possibility of interference. We discuss
our design of a device to perform such network data archiving and have implemented
a prototpe device. We discuss other possible application areas of the design.
}
comment = {
Senior Honors Thesis. Advisor: Sean Smith.
}
}
@TechReport{Dartmouth:TR2001-399,
author = {Shan Jiang },
title = {{WebALPS Implementation and Performance Analysis: Using Trusted Co-servers to Enhance Privacy and Security of Web Interactions}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-399},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/270/TR2001-399.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/270/TR2001-399.pdf},
abstract = {
The client-server model of the Web poses a fundamental trust issue: clients are forced
to trust in secrecy and correctness of computation occurring at a remote server
of unknown credibility. The current solution for this problem is to use a PKI (Public
Key Infrastructure) system and SSL (Secure Sockets Layer) digital certificates to
prove the claimed identity of a server and establish an authenticated, encrypted
channel between the client and this server. However, this approach does not address
the security risks posed by potential malicious server operators or any third parties
who may penetrate the server sites.
The WebALPS (Web Applications with Lots of Privacy and Security) approach is proposed
to address these weaknesses by moving sensitive computations at server side into
trusted co-servers running inside high-assurance secure coprocessors.
In this report, we examine the foundations of the credibility of WebALPS co-servers.
Then we will describe our work of designing and building a prototype WebALPS co-server,
which is integrated into the widely-deployed, commercial-grade Apache server. We
will also present the performance test results of our system which support the argument
that WebALPS approach provides a systematic and practical way to address the remote
trust issue.
}
comment = {
Master's thesis.
}
}
@TechReport{Dartmouth:TR2001-398,
author = {David Marmaros },
title = {{A System for Audio Personalization with Applications on Wireless Devices}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-398},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/269/TR2001-398.pdf},
abstract = {
We present and analyze a system for dynamically tailoring discrete audio content
for numerous users based on aggregate data and intuitive feedback mechanisms. The
framework for this system utilizes a flexible client-server architecture to facilitate
audio dissemination, with particular attention to distribution over wireless networks.
We discuss the requirements and specifications of such a system. We further analyze
the algorithms and protocols required for its operation. Finally, we outline and
provide data from a demonstration of this application.
}
comment = {
Senior Honors Thesis. Advisors: David Kotz and Daniela Rus.
}
}
@TechReport{Dartmouth:TR2001-397,
author = {Guanling Chen and David Kotz },
title = {{Supporting Adaptive Ubiquitous Applications with the SOLAR System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-397},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/268/TR2001-397.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/268/TR2001-397.pdf},
abstract = {
As we embed more computers into our daily environment, ubiquitous computing promises
to make them less noticeable and help to prevent information overload. We see, however,
few ubiquitous applications that are able to adapt to the dynamics of user, physical,
and computational context. We believe that there are two challenges causing this
lack of ubiquitous applications: there is no flexible and scalable way to support
information collection and dissemination in a ubiquitous and mobile environment,
and there is no general approach to building adaptive applications given heterogeneous
contextual information. We propose a system infrastructure, Solar, to meet these
challenges. Solar uses a subscription-based operator graph abstraction and allows
dynamic composition of stackable operators to manage ubiquitous information sources.
After developing a set of diverse adaptive applications, we expect to identify fundamental
techniques for context-aware adaptation. Our expectation is that Solar's end-to-end
support for information collection, dissemination, and utilization will make it
easy to build adaptive applications for a ubiquitous mobile environment with many
users and devices.
}
}
@TechReport{Dartmouth:TR2001-396,
author = {Tiffany M. Wong },
title = {{Implementing a Database Information System for an Electronic Baseball Scorecard}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-396},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/267/TR2001-396.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/267/TR2001-396.pdf},
abstract = {
We present our design and implementation of a database system of information storage
and retrieval for an electronic baseball scorecard. The program uses the relational
MySQL database to hold information and a Tcl API to handle interactions between
the database and the user interface code. This paper discusses the inner workings
of how information storage was broken down inside the database, how queries were
internally constructed in accordance with the user's input, and how statistics for
players and teams were calculated and returned to the user. Finally, we discuss
some limitations attached to our current implementation of the program and propose
improvements that can be made in future versions.
}
comment = {
Senior Honors Thesis. Advisor: Tom Cormen
}
}
@TechReport{Dartmouth:TR2001-395,
author = {Tiffany M. Wong },
title = {{An Implementation of Object-Oriented Program Transformation for Thought-Guided Debugging}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-395},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/266/TR2001-395.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/266/TR2001-395.pdf},
abstract = {
This paper presents our design and implementation of program transformation for C++
that will be used in the context of a thought-guided debugging system. The program
uses a lexical analyzer written in Flex and a grammar written in Bison that work
in conjunction to scan the inputted C++ code for function definitions and class
definitions. The code is then transformed to produce trace information for each
defined function, while the original functionality of the code is left untouched.
We also implement two additional data structures that are used for information storage
during the course of the program.
}
comment = {
Senior Honors Thesis. Advisor: Tom Cormen
}
}
@TechReport{Dartmouth:TR2001-394,
author = {David D. Latham },
title = {{An Empirical Study of Training and Testing Error in Boosting}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-394},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/265/TR2001-394.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/265/TR2001-394.pdf},
abstract = {
Bounds have been proven for both training and testing error for the boosting algorithm
AdaBoost, but in practice neither seem to produce a particularly tight bound. In
this paper we share some observations of these bounds from empirical results, and
then explore some properties of the algorithm with an eye towards finding an improved
bound for the performance of AdaBoost. Based on our empirical evidence, the error
of a hypothesis which labels examples probabilistically based upon the confidence
of the vote of the weak hypotheses forms a tighter bound for the training error.
}
comment = {
Senior Honors Thesis. Advisor: Jay Aslam.
}
}
@TechReport{Dartmouth:TR2001-393,
author = {Pablo Stern },
title = {{Measuring early usage of Dartmouth's wireless network}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-393},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/264/TR2001-393.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/264/TR2001-393.pdf},
abstract = {
In Spring 2001, Dartmouth College installed a campus-wide 802.11b wireless network.
To understand how that network is used, we examined the usage characteristics of
the network over a five-week period. We monitored access points to determine user
behavior, and user and network traffic characteristics. Because our study coincided
with the deployment of the access points, our analysis captures the growth of a
wireless network. The results of this study help understand the behavior of mobile
users and provide a reference to network engineers wishing to deploy and expand
similar wireless networks.
}
comment = {
Senior Honors Thesis. Advisor: David Kotz.
}
}
@TechReport{Dartmouth:TR2001-392,
author = {Arun Mathias },
title = {{SmartReminder: A Case Study on Context-Sensitive Applications}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-392},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/263/TR2001-392.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/263/TR2001-392.pdf},
abstract = {
Designing context-sensitive applications is challenging. We design and implement
SmartReminder to explore designing context-sensitive applications and to demonstrate
how the SOLAR system can be used in developing such applications. SmartReminder
is an application that reminds the user based on contextual information. Current
appointment-reminder applications remind the user about their appointments at an
arbitrarily specified time. For instance, they might remind the user ten minutes
before each appointment. SmartReminder, on the other hand, uses contextual information,
like location, to better estimate the appropriate reminder time for each appointment.
It reminds the user based on where they are, where they need to be, and how long
it will take them to get there. This paper presents SmartReminder as an illustration
of how context-sensitive applications can be designed using the SOLAR system for
dissemination of contextual information.
}
comment = {
Senior Honors Thesis. Advisor: David Kotz.
}
}
@TechReport{Dartmouth:TR2001-391,
author = {Ammar Khalid },
title = {{A Directory Infrastructure to Support Mobile Services}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-391},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/262/TR2001-391.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/262/TR2001-391.pdf},
abstract = {
Traditional Voice-over-IP applications such as Microsoft NetMeeting assume that the
user is on a machine with a fixed IP address. If, however, the user connects to
the Internet, via a wireless network, on a handheld device, his IP address frequently
changes as he moves from one subnet to another. In such a situation, we need a service
that can be queried for the most current IP address of a person whom we wish to
contact. In this project, we design and implement such a directory service. The
service authenticates all callers and callees, is robust against most host failure,
and scales to several thousand registered users.
}
comment = {
Senior Honors Thesis. Advisor: David Kotz.
}
}
@TechReport{Dartmouth:TR2001-390,
author = {G. Ayorkor Mills-Tettey },
title = {{Mobile Voice Over IP (MVOIP): An Application-level Protocol}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-390},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/261/TR2001-390.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/261/TR2001-390.pdf},
abstract = {
Current Voice over Internet Protocol (VOIP) protocols require participating hosts
to have fixed IP addresses for the duration of a VOIP call. When using a wireless-enabled
host, such as a tablet computer on an 802.11 wireless network, it is possible for
a participant in a VOIP call to roam around the network, moving from one subnet
to another and needing to change IP addresses. This address change creates the need
for mobility support in VOIP applications. We present the design of Mobile Voice
over IP (MVOIP), an application-level protocol that enables such mobility in a VOIP
application based on the ITU H.323 protocol stack. An MVOIP application uses hints
from the surrounding network to determine that it has switched subnets. It then
initiates a hand-off procedure that comprises pausing its current calls, obtaining
a valid IP address for the current subnet, and reconnecting to the remote party
with whom it was in a call. Testing the system shows that on a Windows 2000 platform
there is a perceivable delay in the hand-off process, most of which is spent in
the Windows API for obtaining DHCP addresses. Despite this bottleneck, MVOIP works
well on a wireless network.
}
comment = {
Senior Honors Thesis. Advisor: David Kotz.
}
}
@TechReport{Dartmouth:TR2001-389,
author = {Thomas B. Stephens },
title = {{Improving a Brokering System for Linking Distributed Simulations}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-389},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/260/TR2001-389.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/260/TR2001-389.pdf},
abstract = {
The Agent Based Environment for Linking Simulations (ABELS) is a software framework
designed to provide disparate simulations with dynamically updated data sources.
It allows simulations and other agents to join a "cloud" of interacting producers
and consumers of data. Once they have joined the cloud, they can publish services
to other members and use methods published by others. This paper presents the initial
design of a set of matchmaking components for the ABELS framework. These components
dictate how services describe their abilities and requirements to ABELS. Furthermore,
they help ABELS successfully match data producing services to the requests of data
consuming clients. We begin by describing a system for a data producing service
to describe itself to the ABELS cloud, as well as a corresponding system for a data
consumer to describe its needs. We then describe in detail the three components
that make up the ABELS matchmaking system: the match ranker, which ranks a data
producer's ability to fill the request of a data consumer; the thesaurus, which
helps the match ranker recognize closely related terms; and the unit database, which
allows participants in the ABELS system to translate between related data units.
We also discuss how these basic components can be built upon and improved in future
versions of the ABELS framework.
}
comment = {
Senior Honors Thesis. Advisor: Linda F. Wilson.
}
}
@TechReport{Dartmouth:TR2001-388,
author = {Michael F. Ringenburg },
title = {{Applying the Vector Radix Method to Multidimensional, Multiprocessor, Out-of-Core Fast Fourier Transforms}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-388},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/259/TR2001-388.ps.Z},
abstract = {
We describe an efficient algorithm for calculating Fast Fourier Transforms on matrices
of arbitrarily high dimension using the vector-radix method when the problem size
is out-of-core (i.e., when the size of the data set is larger than the total available
memory of the system). The algorithm takes advantage of multiple processors when
they are present, but it is also efficient on single-processor systems. Our work
is an extension of work done by Lauren Baptist in [Bapt99], which applied the vector-radix
method to 2-dimensional out-of-core matrices.
To determine the effectiveness of the algorithm, we present empirical results as
well as an analysis of the I/O, communication, and computational complexity. We
perform the empirical tests on a DEC 2100 server and on a cluster of Pentium-based
Linux workstations. We compare our results with the traditional dimensional method
of calculating multidimensional FFTs, and show that as the number of dimensions
increases, the vector-radix-based algorithm becomes increasingly effective relative
to the dimensional method.
In order to calculate the complexity of the algorithm, it was necessary to develop
a method for analyzing the interprocessor communication costs of the BMMC data-permutation
algorithm (presented in [CSW98]) used by our FFT algorithms. We present this analysis
method and show how it was derived.
}
comment = {
Masters Thesis. Advisor: Tom Cormen.
}
}
@TechReport{Dartmouth:TR2001-387,
author = {Javed A. Aslam },
title = {{A simple bound on the expected height of a randomly built binary search tree}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-387},
year = {2001},
month = {January},
comment = {
Abstract and paper lost.
}
}
@TechReport{Dartmouth:TR2001-386,
author = {Robert S. Gray and David Kotz and Ronald A. Peterson and Peter Gerken and Martin Hofmann and Daria Chacon and Greg Hill and Niranjan Suri },
title = {{Mobile-Agent versus Client/Server Performance: Scalability in an Information-Retrieval Task}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-386},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/257/TR2001-386.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/257/TR2001-386.pdf},
abstract = {
Mobile agents are programs that can jump from host to host in the network, at times
and to places of their own choosing. Many groups have developed mobile-agent software
platforms, and several mobile-agent applications. Experiments show that mobile agents
can, among other things, lead to faster applications, reduced bandwidth demands,
or less dependence on a reliable network connection. There are few if any studies
of the scalability of mobile-agent servers, particularly as the number of clients
grows. We present some recent performance and scalability experiments that compare
three mobile-agent platforms with each other and with a traditional client/server
approach. The experiments show that mobile agents often outperform client/server
solutions, but also demonstrate the deep interaction between environmental and application
parameters. The three mobile-agent platforms have similar behavior but their absolute
performance varies with underlying implementation choices.
}
comment = {
Revised version appeared in Mobile Agents 2001. See here.
}
}
@TechReport{Dartmouth:TR2001-385,
author = {Xiaowen Liu and David M. Nicol and King Tan },
title = {{Lock-free Scheduling of Logical Processes in Parallel Simulation}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-385},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/256/TR2001-385.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/256/TR2001-385.pdf},
abstract = {
With fixed lookahead information in a simulation model, the overhead of asynchronous
conservative parallel simulation lies in the mechanism used for propagating time
updates in order for logical processes to safely advance their local simulation
clocks. Studies have shown that a good scheduling algorithm should preferentially
schedule processes containing events on the critical path. This paper introduces
a lock-free algorithm for scheduling logical processes in conservative parallel
discrete-event simulation on shared-memory multiprocessor machines. The algorithm
uses fetch&add operations that help avoid inefficiencies associated with using locks.
The lock-free algorithm is robust. Experiments show that, compared with the scheduling
algorithm using locks, the lock-free algorithm exhibits better performance when
the number of logical processes assigned to each processor is small or when the
workload becomes significant. In models with large number of logical processes,
our algorithm shows only modest increase in execution time due to the overhead in
the algorithm for extra bookkeeping.
}
comment = {
A revision of this report appears on PADS 2001.
}
}
@TechReport{Dartmouth:TR2001-384,
author = {Chris Bailey-Kellogg and Naren Ramakrishnan },
title = {{Ambiguity-Directed Sampling for Qualitative Analysis of Sparse Data from Spatially-Distributed Physical Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2001-384},
year = {2001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/255/TR2001-384.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/255/TR2001-384.pdf},
abstract = {
A number of important scientific and engineering applications, such as fluid dynamics
simulation and aircraft design, require analysis of spatially-distributed data from
expensive experiments and complex simulations. In such data-scarce applications,
it is advantageous to use models of given sparse data to identify promising regions
for additional data collection. This paper presents a principled mechanism for applying
domain-specific knowledge to design focused sampling strategies. In particular,
our approach uses ambiguities identified in a multi-level qualitative analysis of
sparse data to guide iterative data collection. Two case studies demonstrate that
this approach leads to highly effective sampling decisions that are also explainable
in terms of problem structures and domain knowledge.
}
}
@TechReport{Dartmouth:TR2000-383,
author = {Hany Farid },
title = {{Reconstructing Ancient Egyptian Tombs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-383},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/254/TR2000-383.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/254/TR2000-383.pdf},
abstract = {
From the pyramids of Giza to the tombs of Thebes (modern Luxor), ancient Egypt's
glorious history has produced remarkable architecture. Sadly, the nearly four million
yearly tourists have taken a heavy toll on many of these ancient structures. Of
particular concern are many of the tombs located opposite to Luxor on the western
bank of the Nile. Digital reconstruction of these tombs has the potential to help
document and preserve these important historical structures. Photographing and reconstruction
of these tombs poses new and unique problems that this paper begins to address.
Techniques for removing image distortions, recovering 3-D shape, and correcting
for lighting imbalances are discussed. A complete reconstruction of the tomb of
Sennedjem is shown.
}
}
@TechReport{Dartmouth:TR2000-382,
author = {Javed A. Aslam and Mark Montague },
title = {{Bayes Optimal Metasearch: A Probabilistic Model for Combining the Results of Multiple Retrieval Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-382},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/253/TR2000-382.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/253/TR2000-382.pdf},
abstract = {
We introduce a new, probabilistic model for combining the outputs of an arbitrary
number of query retrieval systems. By gathering simple statistics on the average
performance of a given set of query retrieval systems, we construct a Bayes optimal
mechanism for combining the outputs of these systems. Our construction yields a
metasearch strategy whose empirical performance nearly always exceeds the performance
of any of the constituent systems. Our construction is also robust in the sense
that if ``good'' and ``bad'' systems are combined, the performance of the composite
is still on par with, or exceeds, that of the best constituent system. Finally,
our model and theory provide theoretical and empirical avenues for the improvement
of this metasearch strategy.
}
comment = {
Preliminary version appeared in SIGIR 2000.
}
}
@TechReport{Dartmouth:TR2000-381,
author = {Guanling Chen and David Kotz },
title = {{A Survey of Context-Aware Mobile Computing Research}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-381},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/252/TR2000-381.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/252/TR2000-381.pdf},
abstract = {
Context-aware computing is a mobile computing paradigm in which applications can
discover and take advantage of contextual information (such as user location, time
of day, nearby people and devices, and user activity). Since it was proposed about
a decade ago, many researchers have studied this topic and built several context-aware
applications to demonstrate the usefulness of this new technology. Context-aware
applications (or the system infrastructure to support them), however, have never
been widely available to everyday users. In this survey of research on context-aware
systems and applications, we looked in depth at the types of context used and models
of context information, at systems that support collecting and disseminating context,
and at applications that adapt to the changing context. Through this survey, it
is clear that context-aware research is an old but rich area for research. The difficulties
and possible solutions we outline serve as guidance for researchers hoping to make
context-aware computing a reality.
}
}
@TechReport{Dartmouth:TR2000-380,
author = {Jon Howell },
title = {{Naming and sharing resources across administrative boundaries (errata)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-380},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/251/TR2000-380.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/251/TR2000-380.pdf},
abstract = {
I tackle the problem of naming and sharing resources across administrative boundaries.
Conventional systems manifest the hierarchy of typical administrative structure
in the structure of their own mechanism. While natural for communication that follows
hierarchical patterns, such systems interfere with naming and sharing that cross
administrative boundaries, and therefore cause headaches for both users and administrators.
I propose to organize resource naming and security, not around administrative domains,
but around the sharing patterns of users.
The dissertation is organized into four main parts. First, I discuss the challenges
and tradeoffs involved in naming resources and consider a variety of existing approaches
to naming.
Second, I consider the architectural requirements for user-centric sharing. I evaluate
existing systems with respect to these requirements.
Third, to support the sharing architecture, I develop a formal logic of sharing
that captures the notion of restricted delegation. Restricted delegation ensures
that users can use the same mechanisms to share resources consistently, regardless
of the origin of the resource, or with whom the user wishes to share the resource
next. A formal semantics gives unambiguous meaning to the logic. I apply the formalism
to the Simple Public Key Infrastructure and discuss how the formalism either supports
or discourages potential extensions to such a system.
Finally, I use the formalism to drive a user-centric sharing implementation for
distributed systems. I show how this implementation enables end-to-end authorization,
a feature that makes heterogeneous distributed systems more secure and easier to
audit. Conventionally, gateway services that bridge administrative domains, add
abstraction, or translate protocols typically impede the flow of authorization information
from client to server. In contrast, end-to-end authorization enables us to build
gateway services that preserve authorization information, hence we reduce the size
of the trusted computing base and enable more effective auditing. I demonstrate
my implementation and show how it enables end-to-end authorization across various
boundaries. I measure my implementation and argue that its performance tracks that
of similar authorization mechanisms without end-to-end structure.
I conclude that my user-centric philosophy of naming and sharing benefits both users
and administrators.
}
comment = {
This technical report contains errata for the dissertation. Volume One (187 pages)
is the heart of the dissertation. Volume Two (237 pages) contains a software manual
introduced with illustrated code fragments, plus plots of the raw data used for
the experimental results presented in Volume One. That material is optional; I recommend
that the interested reader begin with just Volume One. Volume I is available as
TR2000-378. Volume II is available as TR2000-379.
}
}
@TechReport{Dartmouth:TR2000-379,
author = {Jon Howell },
title = {{Naming and sharing resources across administrative boundaries (Volume II)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-379},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/250/TR2000-379.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/250/TR2000-379.pdf},
abstract = {
I tackle the problem of naming and sharing resources across administrative boundaries.
Conventional systems manifest the hierarchy of typical administrative structure
in the structure of their own mechanism. While natural for communication that follows
hierarchical patterns, such systems interfere with naming and sharing that cross
administrative boundaries, and therefore cause headaches for both users and administrators.
I propose to organize resource naming and security, not around administrative domains,
but around the sharing patterns of users.
The dissertation is organized into four main parts. First, I discuss the challenges
and tradeoffs involved in naming resources and consider a variety of existing approaches
to naming.
Second, I consider the architectural requirements for user-centric sharing. I evaluate
existing systems with respect to these requirements.
Third, to support the sharing architecture, I develop a formal logic of sharing
that captures the notion of restricted delegation. Restricted delegation ensures
that users can use the same mechanisms to share resources consistently, regardless
of the origin of the resource, or with whom the user wishes to share the resource
next. A formal semantics gives unambiguous meaning to the logic. I apply the formalism
to the Simple Public Key Infrastructure and discuss how the formalism either supports
or discourages potential extensions to such a system.
Finally, I use the formalism to drive a user-centric sharing implementation for
distributed systems. I show how this implementation enables end-to-end authorization,
a feature that makes heterogeneous distributed systems more secure and easier to
audit. Conventionally, gateway services that bridge administrative domains, add
abstraction, or translate protocols typically impede the flow of authorization information
from client to server. In contrast, end-to-end authorization enables us to build
gateway services that preserve authorization information, hence we reduce the size
of the trusted computing base and enable more effective auditing. I demonstrate
my implementation and show how it enables end-to-end authorization across various
boundaries. I measure my implementation and argue that its performance tracks that
of similar authorization mechanisms without end-to-end structure.
I conclude that my user-centric philosophy of naming and sharing benefits both users
and administrators.
}
comment = {
This technical report represents Volume Two of the dissertation. Volume One (187
pages) is the heart of the dissertation. Volume Two (237 pages) contains a software
manual introduced with illustrated code fragments, plus plots of the raw data used
for the experimental results presented in Volume One. That material is optional;
I recommend that the interested reader begin with just Volume One. Volume I is available
as TR2000-378. Please note that a list of errata is available as TR2000-380.
}
}
@TechReport{Dartmouth:TR2000-378,
author = {Jon Howell },
title = {{Naming and sharing resources across administrative boundaries (Volume I)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-378},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/249/TR2000-378.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/249/TR2000-378.pdf},
abstract = {
I tackle the problem of naming and sharing resources across administrative boundaries.
Conventional systems manifest the hierarchy of typical administrative structure
in the structure of their own mechanism. While natural for communication that follows
hierarchical patterns, such systems interfere with naming and sharing that cross
administrative boundaries, and therefore cause headaches for both users and administrators.
I propose to organize resource naming and security, not around administrative domains,
but around the sharing patterns of users.
The dissertation is organized into four main parts. First, I discuss the challenges
and tradeoffs involved in naming resources and consider a variety of existing approaches
to naming.
Second, I consider the architectural requirements for user-centric sharing. I evaluate
existing systems with respect to these requirements.
Third, to support the sharing architecture, I develop a formal logic of sharing
that captures the notion of restricted delegation. Restricted delegation ensures
that users can use the same mechanisms to share resources consistently, regardless
of the origin of the resource, or with whom the user wishes to share the resource
next. A formal semantics gives unambiguous meaning to the logic. I apply the formalism
to the Simple Public Key Infrastructure and discuss how the formalism either supports
or discourages potential extensions to such a system.
Finally, I use the formalism to drive a user-centric sharing implementation for
distributed systems. I show how this implementation enables end-to-end authorization,
a feature that makes heterogeneous distributed systems more secure and easier to
audit. Conventionally, gateway services that bridge administrative domains, add
abstraction, or translate protocols typically impede the flow of authorization information
from client to server. In contrast, end-to-end authorization enables us to build
gateway services that preserve authorization information, hence we reduce the size
of the trusted computing base and enable more effective auditing. I demonstrate
my implementation and show how it enables end-to-end authorization across various
boundaries. I measure my implementation and argue that its performance tracks that
of similar authorization mechanisms without end-to-end structure.
I conclude that my user-centric philosophy of naming and sharing benefits both users
and administrators.
}
comment = {
This technical report represents Volume One of the dissertation. Volume One (187
pages) is the heart of the dissertation. Volume Two (237 pages) contains a software
manual introduced with illustrated code fragments, plus plots of the raw data used
for the experimental results presented in Volume One. That material is optional;
I recommend that the interested reader begin with just Volume One. Volume II is
available as TR2000-379. Please note that a list of errata is available as TR2000-380.
}
}
@TechReport{Dartmouth:TR2000-377,
author = {David Kotz and George Cybenko and Robert S. Gray and Guofei Jiang and Ronald A. Peterson and Martin O. Hofmann and Daria A. Chacon and Kenneth R. Whitebread and James Hendler },
title = {{Performance Analysis of Mobile Agents for Filtering Data Streams on Wireless Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-377},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/248/TR2000-377.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/248/TR2000-377.pdf},
abstract = {
Wireless networks are an ideal environment for mobile agents, since their mobility
allows them to move across an unreliable link to reside on a wired host, next to
or closer to the resources that they need to use. Furthermore, client-specific data
transformations can be moved across the wireless link and run on a wired gateway
server, reducing bandwidth demands. In this paper we examine the tradeoffs faced
when deciding whether to use mobile agents in a data-filtering application where
numerous wireless clients filter information from a large data stream arriving across
the wired network. We develop an analytical model and use parameters from filtering
experiments conducted during a U.S. Navy Fleet Battle Experiment (FBE) to explore
the model's implications.
}
comment = {
Updated version of TR2000-366. To appear, after revisions, in the journal Mobile
Networks and Applications (ACM MONET).
}
}
@TechReport{Dartmouth:TR2000-376,
author = {Martin Mundhenk },
title = {{The complexity of planning with partially-observable Markov decision processes}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-376},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/247/TR2000-376.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/247/TR2000-376.pdf},
abstract = {
This work surveys results on the complexity of planning under uncertainty. The planning
model considered is the partially-observable Markov decision process. The general
planning problems are, given such a process, (a) to calculate its performance under
a given control policy, (b) to find an optimal or approximate optimal control policy,
and (c) to decide whether a good policy exists. The complexity of this and related
problems depend on a variety of factors, including the observability of the process
state,
the compactness of the process representation, the type of policy, or even the number
of actions relative to the number of states. In most cases, the problem can be shown
to be complete for some known complexity class.
The skeleton of this survey are results from Littman, Goldsmith and Mundhenk (Journal
of Artificial Intelligence Research 1998), Mundhenk (Mathematics of Operations Research
2000), Mundhenk, Goldsmith, Lusena and Allender (Journal of the ACM 2000), and Lusena,
Goldsmith and Mundhenk (University of KY CS TR). But there are also some news.
}
}
@TechReport{Dartmouth:TR2000-375,
author = {Ezra E. K. Cooper and Robert S. Gray },
title = {{An Economic CPU-Time Market for D'Agents}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-375},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/246/TR2000-375.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/246/TR2000-375.pdf},
abstract = {
A usable and efficient resource-management system has been created for use with D'Agents.
The software dynamically negotiates a price rate for CPU time, using the competitive
bids of mobile agents that offer currency in return for fast computation. The system
allows mobile agents to plan their expenditures across many hosts while minimizing
the time needed for their tasks. The ability to price CPU time opens the door for
service owners to be compensated for the computation consumed by agents and provides
an incentive for servers to allow anonymous agents. We discuss the theoretical background
which makes a CPU market system possible and the performance of the D'Agents market
system.
}
comment = {
Undergraduate honors thesis. Advisor: Bob Gray.
}
}
@TechReport{Dartmouth:TR2000-373,
author = {David B. Martin },
title = {{Depth from Flash}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-373},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/245/TR2000-373.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/245/TR2000-373.pdf},
abstract = {
Digital camera technology has recently seen substantial improvements in image quality
while lower prices have made it affordable to the average consumer. Camera manufacturers,
however, are not taking full advantage of this new medium for image capture. By
filtering the already digitized image produced by these cameras through on-board
image processing algorithms we can dramatically increase the power of digital cameras.
For example, according to experts in the photographic industry, most people simply
take bad pictures. Classic examples of this phenomenon are photographs taken indoors
with a point-and-shoot style camera using its built-in flash. The subjects of these
photographs often seem to have a spotlight on them, making them look bright and
washed out while the rest of the photograph is dark and indistinct. This can primarily
be accounted for by a well known property of point light sources: falloff in brightness
is inversely proportional to the square of the distance between the light and the
object being illuminated. A technique first introduced in the field of computer
vision has been shown to successfully recover information about the distance between
the light source and objects in the world. We propose using this technique, which
is readily implementable in hardware, to correct for a variety of poorly illuminated
digital images.
}
comment = {
Undergraduate Honors Thesis. Advisor: Hany Farid
}
}
@TechReport{Dartmouth:TR2000-372,
author = {John C. Artz },
title = {{Personal Radio}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-372},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/244/TR2000-372.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/244/TR2000-372.pdf},
abstract = {
With the development of new technologies that allow the broadcast of digital data
over radio signals, there are many possibilities for improving upon the traditional
radio station model for content delivery. The idea of Personal Radio is a system
that tailors content to meet the needs of each individual. Using Global Positioning
System (GPS) technology to play location specific content, the listening history
to play content an appropriate number of times, and user feedback to learn personal
preferences, the Personal Radio provides the listener with the content that is the
most useful/interesting to them. This paper will examine the general design of such
a system and present solutions developed in the implementation of several pieces
of the design.
}
comment = {
Undergraduate Honors Thesis. Advisors: David Kotz and Daniela Rus
}
}
@TechReport{Dartmouth:TR2000-370,
author = {Debbie O. Chyi },
title = {{An Infrastructure for a Mobile-Agent System that Provides Personalized Services to Mobile Devices}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-370},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/243/TR2000-370.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/243/TR2000-370.pdf},
abstract = {
In this paper, we present the design of a mobile-agent system that provides a mobile
user with a personalized information retrieval service and we describe the implementation
of the infrastructure for such a system. This "Personal Agent System" gathers information
from the Internet and uses context-aware mechanisms to manage the information according
to a mobile user's needs and preferences. The user's schedule and location are the
context indicators in this system. These indicators are critical in ensuring that
users obtain only the information they want, receive information in a form that
is most useful for viewing on their mobile device, and is notified of new information
in a minimally intrusive manner. The system incorporates a rule-based learning system
to enhance the personalization achieved by the system.
}
comment = {
Undergraduate Honors Thesis. Advisor: David F. Kotz
}
}
@TechReport{Dartmouth:TR2000-369,
author = {Karolyn A. Abram },
title = {{Registration of Images with Dissimilar Contrast using a Hybrid Method Employing Correlation and Mutual Information}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-369},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/242/TR2000-369.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/242/TR2000-369.pdf},
abstract = {
The problem of fitting one image into another is commonly called "registration."
Finding the best possible translation and rotation necessary to align two images
is one approach to solving this problem. Registration is a crucial component of
many remote sensing and medical image interpretation applications. Image alignment
techniques aid in volumetric estimations of complicated structures and allow radiologists
to accurately identify changes between sequential images. Radiologists require image
alignment capabilities to correct for patient motion and/or content displacement
between images.
Numerous image registration techniques exist for correcting the alignment problems
mentioned above. Unfortunately, most of these techniques, such as Correlation, fail
to find a good alignment when dealing with images that differ in contrast. The Mutual
Information method is able to align images independently of contrast, but it is
computationally intensive. We explore a hybrid technique that utilizes both Correlation
and Mutual Information. The Hybrid technique hopes to gain greater contrast independence
than Correlation alone while achieving a lower running time than a pure Mutual Information
technique.
}
comment = {
Undergraduate Honors Thesis Advisor: Daniel N. Rockmore
}
}
@TechReport{Dartmouth:TR2000-368,
author = {Eric Michael Greenberg },
title = {{A Simulation of Auroral Absorption}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-368},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/241/TR2000-368.pdf},
abstract = {
HF radio transmissions propagate long distances by reflecting off the ionosphere.
At high latitudes radio propagation is strongly affected by the northern lights
(aurora borealis), which causes ionization at low altitudes and hence the absorption
of radio waves. Models of this process are still in a primitive state. A simulation
of radio wave propagation was created in order to test Foppiano and Bradley's empirical
model of auroral absorption. The simulation attempts to predict the net absorption
of signals at a receiver by simulating a large number of transmitters, even though
the exact sources of the signals are unknown. Although the simulation takes into
account auroral and nonauroral absorption as well as other sources of path loss,
the analysis focuses on the nighttime aurora. An intelligent search algorithm is
used in order to efficiently adjust the model to best fit the data. The output of
the simulation is qualitatively and quantitatively compared to signal levels observed
with HF radio receivers located in northern Canada. The analysis allows us to develop
alternative models of auroral absorption which account for the level of geomagnetic
activity, and these are compared to the standard Foppiano and Bradley model.
}
comment = {
Advisor: Dan Rockmore
}
}
@TechReport{Dartmouth:TR2000-367,
author = {Cliff Stein and David P. Wagner },
title = {{Approximation Algorithms for the Minimum Bends Traveling Salesman Problem}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-367},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/240/TR2000-367.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/240/TR2000-367.pdf},
abstract = {
The problem of traversing a set of points in the order that minimizes the total distance
traveled (traveling salesman problem) is one of the most famous and well-studied
problems in combinatorial optimization. It has many applications, and has been a
testbed for many of the must useful ideas in algorithm design and analysis. The
usual metric, minimizing the total distance traveled, is an important one, but many
other metrics are of interest.
In this paper, we introduce the metric of minimizing the number of turns in the
tour, given that the input points are in the Euclidean plane. To our knowledge this
metric has not been studied previously. It is motivated by applications in robotics
and in the movement of other heavy machinery: for many such devices turning is an
expensive operation. We give approximation algorithms for several variants of the
traveling salesman problem for which the metric is to minimize the number of turns.
We call this the minimum bends traveling salesman problem.
For the case of an arbitrary set of $n$ points in the Euclidean plane, we give an
O(lg z)-approximation algorithm, where z is the maximum number of collinear points.
In the worst case z can be as big as n, but z will often be much smaller. For the
case when the lines are restricted to being either horizontal or vertical, we give
a 2-approximation algorithm. If we have the further restriction that no two points
are allowed to have the same x- or y-coordinate, we give an algorithm that finds
a tour which makes at most two turns more than the optimal tour. Thus we have an
approximation algorithm with an additive, rather than a multiplicative error bound.
Beyond the additive error bound, our algorithm for this problem introduces several
interesting algorithmic techniques for decomposing sets of points in the Euclidean
plane that we believe to be of independent interest.
}
comment = {
Submitted to FOCS 2000.
}
}
@TechReport{Dartmouth:TR2000-366,
author = {David Kotz and Guofei Jiang and Robert S. Gray and George Cybenko and Ronald A. Peterson },
title = {{Performance Analysis of Mobile Agents for Filtering Data Streams on Wireless Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-366},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/239/TR2000-366.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/239/TR2000-366.pdf},
abstract = {
Wireless networks are an ideal environment for mobile agents, because their mobility
allows them to move across an unreliable link to reside on a wired host, next to
or closer to the resources they need to use. Furthermore, client-specific data transformations
can be moved across the wireless link, and run on a wired gateway server, with the
goal of reducing bandwidth demands. In this paper we examine the tradeoffs faced
when deciding whether to use mobile agents to support a data-filtering application,
in which numerous wireless clients filter information from a large data stream arriving
across the wired network. We develop an analytical model and use parameters from
our own experiments to explore the model's implications.
}
comment = {
In August 2000 a revised version appeared in the International Workshop on Modeling
and Simulation of Wireless and Mobile Systems (MSWiM 2000). In October 2000 a further
revised version appeared as Dartmouth Technical Report TR2000-377, and was submitted
to the journal Mobile Networks and Applications (ACM MONET).
}
}
@TechReport{Dartmouth:TR2000-365,
author = {Robert S. Gray and David Kotz and George Cybenko and Daniela Rus },
title = {{Mobile Agents: Motivations and State-of-the-Art Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-365},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/238/TR2000-365.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/238/TR2000-365.pdf},
abstract = {
A mobile agent is an executing program that can migrate, at times of its own choosing,
from machine to machine in a heterogeneous network. On each machine, the agent interacts
with stationary service agents and other resources to accomplish its task. In this
chapter, we first make the case for mobile agents, discussing six strengths of mobile
agents and the applications that benefit from these strengths. Although none of
these strengths are unique to mobile agents, no competing technique shares all six.
In other words, a mobile-agent system provides a single general framework in which
a wide range of distributed applications can be implemented efficiently and easily.
We then present a representative cross-section of current mobile-agent systems.
}
comment = {
This technical report will appear as a chapter in Jeffrey M. Bradshaw, editor, Handbook
of Agent Technology, AAAI/MIT Press, 2000. In Press.
}
}
@TechReport{Dartmouth:TR2000-364,
author = {Jon Howell and Keith Kotay },
title = {{Landmarks for absolute localization}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-364},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/237/TR2000-364.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/237/TR2000-364.pdf},
abstract = {
For certain experiments in mobile robotics, it is convenient to eliminate positional
estimation error in the interest of analyzing other parts of the experiment. We
designed and implemented a simple, accurate scheme for encoding and recovering absolute
position information. The encoding is a two-dimensional image printed on the plane
of the floor, and the absolute position information is recovered using a downward-looking
video camera mounted on a mobile robot.
}
comment = {
This document describes work done in the Dartmouth Robotics Laboratory in April of
1997 and August of 1999. It was previously ``published'' as a web page, but we thought
it would make sense to document it more permanently.
}
}
@TechReport{Dartmouth:TR2000-363,
author = {Jon Howell and David Kotz },
title = {{A Formal Semantics for SPKI}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-363},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/236/TR2000-363.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/236/TR2000-363.pdf},
abstract = {
We extend the logic and semantics of authorization due to Abadi, Lampson, et al.
to support restricted delegation. Our formal model provides a simple interpretation
for the variety of constructs in the Simple Public Key Infrastructure (SPKI), and
lends intuition about possible extensions. We discuss both extensions that our semantics
supports and extensions that it cautions against.
}
comment = {
This TR supercedes TR1999-361. This technical report is an extended version of a
paper submitted to ESORICS 2000. For more information, see the project
web page.
}
}
@TechReport{Dartmouth:TR2000-362,
author = {Chris Bailey-Kellogg and John J. Kelley and Clifford Stein and Bruce Randall Donald },
title = {{Reducing Mass Degeneracy in SAR by MS by Stable Isotopic Labeling}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {TR2000-362},
year = {2000},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/235/TR2000-362.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/235/TR2000-362.pdf},
abstract = {
Mass spectrometry (MS) promises to be an invaluable tool for functional genomics,
by supporting low-cost, high-throughput experiments. However, large-scale MS faces
the potential problem of mass degeneracy -- indistinguishable masses for multiple
biopolymer fragments (e.g. from a limited proteolytic digest). This paper studies
the tasks of planning and interpreting MS experiments that use selective isotopic
labeling, thereby substantially reducing potential mass degeneracy. Our algorithms
support an experimental-computational protocol called Structure-Activity Relation
by Mass Spectrometry (SAR by MS), for elucidating the function of protein-DNA and
protein-protein complexes. SAR by MS enzymatically cleaves a crosslinked complex
and analyzes the resulting mass spectrum for mass peaks of hypothesized fragments.
Depending on binding mode, some cleavage sites will be shielded; the absence of
anticipated peaks implicates corresponding fragments as either part of the interaction
region or inaccessible due to conformational change upon binding. Thus different
mass spectra provide evidence for different structure-activity relations. We address
combinatorial and algorithmic questions in the areas of data analysis (constraining
binding mode based on mass signature) and experiment planning (determining an isotopic
labeling strategy to reduce mass degeneracy and aid data analysis). We explore the
computational complexity of these problems, obtaining upper and lower bounds. We
report experimental results from implementations of our algorithms.
}
comment = {
This report supercedes TR99-359.
To appear in the 8th International Conference
on Intelligent Systems for Molecular Biology, (August 20-23, 2000) La Jolla,
CA (Accepted; in press).
}
}
@TechReport{Dartmouth:PCS-TR99-361,
author = {Jon Howell and David Kotz },
title = {{An Access-Control Calculus for Spanning Administrative Domains}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-361},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/234/TR99-361.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/234/TR99-361.pdf},
abstract = {
In our quest to give users uniform access to resources unimpeded by administrative
boundaries, we discovered that we needed transitive sharing among users, with the
possibility of restricted access along each sharing link. To achieve that goal,
we extend Lampson et al.'s calculus for access control to support restricted delegations.
We discuss the advantages of our extension, including the simplification of constructs
like ACLs and statement expiration. We also apply our extension to model the Simple
Public Key Infrastructure and make suggestions about its future development. Our
extended calculus exposes some surprising consequences in such systems that use
restricted delegation.
}
comment = {
Superceded by TR2000-363.
}
}
@TechReport{Dartmouth:PCS-TR99-360,
author = {Jonathan Bredin and Rajiv T. Maheswaran and Cagri Imer and Tamer Basar and David Kotz and Daniela Rus },
title = {{A Game-Theoretic Formulation of Multi-Agent Resource Allocation}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-360},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/233/TR99-360.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/233/TR99-360.pdf},
abstract = {
This paper considers resource allocation in a network with mobile agents competing
for computational priority. We formulate this problem as a multi-agent game with
the players being agents purchasing service from a common server. We show that there
exists a computable Nash equilibrium when agents have perfect information into the
future. We simulate a network of hosts and agents using our strategy to show that
our resource-allocation mechanism effectively prioritizes agents according to their
endowments.
}
comment = {
Submitted to "Autonomous Agents 2000". See related
papers.
}
}
@TechReport{Dartmouth:PCS-TR99-359,
author = {Bruce Randall Donald and Chris Bailey-Kellogg and John J. Kelley and Clifford Stein },
title = {{SAR by MS for Functional Genomics (Structure-Activity Relation by Mass Spectrometry)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-359},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/232/TR99-359.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/232/TR99-359.pdf},
abstract = {
Large-scale functional genomics will require fast, high-throughput experimental techniques,
coupled with sophisticated computer algorithms for data analysis and experiment
planning. In this paper, we introduce a combined experimental-computational protocol
called Structure-Activity Relation by Mass Spectrometry (SAR by MS), which
can be used to elucidate the function of protein-DNA or protein-protein complexes.
We present algorithms for SAR by MS and analyze their complexity. Carefully-designed
Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI TOF) and Electrospray
Ionization (ESI) assays require only femtomolar samples, take only microseconds
per spectrum to record, enjoy a resolution of up to one dalton in $10^6$, and (in
the case of MALDI) can operate on protein complexes up to a megadalton in mass.
Hence, the technique is attractive for high-throughput functional genomics.
In SAR by MS, selected residues or nucleosides are 2H-, 13C-, and/or 15N-labeled.
Second, the complex is crosslinked. Third, the complex is cleaved with proteases
and/or endonucleases. Depending on the binding mode, some cleavage sites will be
shielded by the crosslinking. Finally, a mass spectrum of the resulting fragments
is obtained and analyzed. The last step is the Data Analysis phase, in
which the mass signatures are interpreted to obtain constraints on the functional
binding mode. Experiment Planning entails deciding what labeling strategy
and cleaving agents to employ, so as to minimize mass degeneracy and spectral overlap,
in order that the constraints derived in data analysis yield a small number of binding
hypotheses.
A number of combinatorial and algorithmic questions arise in deriving algorithms
for both Experiment Planning and Data Analysis. We explore the complexity of these
problems, obtaining upper and lower bounds. Experimental results are reported from
an implementation of our algorithms.
}
comment = {
This report is superceded by
TR2000-362 .
}
}
@TechReport{Dartmouth:PCS-TR99-358,
author = {Chris Bailey-Kellogg and Alik Widge and John J. Kelley and Marcelo J. Berardi and John H. Bushweller and Bruce Randall Donald },
title = {{The NOESY Jigsaw: Automated Protein Secondary Structure and Main-Chain Assignment from Sparse, Unassigned NMR Data}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-358},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/231/TR99-358.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/231/TR99-358.pdf},
abstract = {
High-throughput, data-directed computational protocols for Structural Genomics (or
Proteomics) are required in order to evaluate the protein products of genes for
structure and function at rates comparable to current gene-sequencing technology.
This paper presents the Jigsaw algorithm, a novel high-throughput, automated approach
to protein structure characterization with nuclear magnetic resonance (NMR). Jigsaw
consists of two main components: (1) graph-based secondary structure pattern identification
in unassigned heteronuclear NMR data, and (2) assignment of spectral peaks by probabilistic
alignment of identified secondary structure elements against the primary sequence.
Jigsaw's deferment of assignment until after secondary structure identification
differs greatly from traditional approaches, which begin by correlating peaks among
dozens of experiments. By deferring assignment, Jigsaw not only eliminates this
bottleneck, it also allows the number of experiments to be reduced from dozens to
four, none of which requires 13C-labeled protein. This in turn dramatically reduces
the amount and expense of wet lab molecular biology for protein expression and purification,
as well as the total spectrometer time to collect data.
Our results for three test proteins demonstrate that we are able to identify and
align approximately 80 percent of alpha-helical and 60 percent of beta-sheet structure.
Jigsaw is extremely fast, running in minutes on a Pentium-class Linux workstation.
This approach yields quick and reasonably accurate (as opposed to the traditional
slow and extremely accurate) structure calculations, utilizing a suite of graph
analysis algorithms to compensate for the data sparseness. Jigsaw could be used
for quick structural assays to speed data to the biologist early in the process
of investigation, and could in principle be applied in an automation-like fashion
to a large fraction of the proteome.
}
comment = {
To appear in The Fourth Annual
International Conference on Computational Molecular Biology (RECOMB'2000),
Tokyo, Japan, April 8-11, 2000.
}
}
@TechReport{Dartmouth:PCS-TR99-357,
author = {Jeffrey D. Isaacs and Javed A. Aslam },
title = {{Investigating Measures for Pairwise Document Similarity}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-357},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/230/TR99-357.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/230/TR99-357.pdf},
abstract = {
The need for a more effective similarity measure is growing as a result of the astonishing
amount of information being placed online. Most existing similarity measures are
defined by empirically derived formulas and cannot easily be extended to new applications.
We present a pairwise document similarity measure based on Information Theory, and
present corpus dependent and independent applications of this measure. When ranked
with existing similarity measures over TREC FBIS data, our corpus dependent information
theoretic similarity measure ranked first.
}
comment = {
Undergraduate Honors Thesis. Advisor: Jay Aslam.
}
}
@TechReport{Dartmouth:PCS-TR99-356,
author = {Artem Lifschitz },
title = {{An Environment for the Facilitation of Robotic Programming}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-356},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/229/TR99-356.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/229/TR99-356.pdf},
abstract = {
I have developed, tested, and evaluated a robot programming environment organized
as a library of flexible data structures to facilitate the creation of robotics
programs. Abstractions are the basis of all of the achievements of Computer Science,
and if it were possible to create a truly flexible, generic abstraction for the
programming of robots -- the science of robotics could advance at a faster pace.
For this reason, I have attempted to implement the abstraction of low-level commands,
and the assembling of them into hierarchies of higher-level actions. My libraries
provide mechanisms for the manipulation and queuing of actions, as well as for the
timing of low-level sensing and actuation. I have tested these libraries by implementing
a cooperative multi-agent formation algorithm in the SoccerServer environment. Often,
when a new level of abstraction is introduced -- significant overhead is added.
However, I have conducted experiments to show that there is no significant overhead
in using this system by comparing the performance of SoccerServer agents that have
been programmed using it against the performance of other agents.
}
comment = {
The postscript "paper" is actually a source code listing. The author chose not to
release his written thesis as a Technical Report. The work represents an Undergraduate
Honors Thesis; Advisor: Daniela Rus.
}
}
@TechReport{Dartmouth:PCS-TR99-355,
author = {Hongxia Quan },
title = {{The Implementation of DaSSF OTcl APIs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-355},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/228/TR99-355.pdf},
abstract = {
As an extension of Tcl, Otcl provides basic functionality for object-oriented programming
in scripting language Tcl. We implemented the Otcl APIs for DaSSF (a parallel simulator
software written in C++ at Dartmouth College) using Tclcl software package written
in University of California at Berkeley. This document discussed the issues involved
in the implementation, especially the communications between C++ objects and Otcl
objects required by DaSSF and the naming problems.
}
comment = {
Thesis Advisor: David M. Nicol
}
}
@TechReport{Dartmouth:PCS-TR99-354,
author = {Marisa E. Kolodny },
title = {{Computers, Art and Smart Rooms: A Smart Picture Frame that Senses the Weather and Genetically Evolves Images}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-354},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/227/TR99-354.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/227/TR99-354.pdf},
abstract = {
By using sensors to sense the environment and genetic programming to evolve images,
this thesis explores two methods for developing smart pictures that can be integrated
with a living space. The system presented senses the weather and indoor conditions,
displays current weather and forecast information retrieved from the web, and displays
genetically evolved images. Sensing the weather not only provides the user with
information they might find useful, but also allows the computer to gain a better
understanding of the user which in turn allows the computer to respond more accurately.
Genetic programming allows the computer to better respond to its environment by
evolving fitter programs.
}
comment = {
Undergraduate Honors Thesis. Advisor: Daniela Rus.
}
}
@TechReport{Dartmouth:PCS-TR99-353,
author = {Bruce Randall Donald and Frederick Henle },
title = {{Using Haptic Vector Fields for Animation Motion Control}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-353},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/226/TR99-353.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/226/TR99-353.pdf},
abstract = {
We are exploring techniques for animation authoring and editing using a haptic force-feedback
device. In our system, a family of animations is encoded by a bundle of trajectories.
This bundle in turn defines a time-varying, higher-order vector field on a configuration
space for the animation. A haptic input device provides a low-dimensional parameterization
of the resulting dynamical system, and the haptic force feedback permits browsing
and editing of the space of animations, by allowing the user to experience the vector
field as physical forces.
}
}
@TechReport{Dartmouth:PCS-TR99-352,
author = {Jason M. Whaley },
title = {{An Application of Word Sense Disambiguation to Information Retrieval}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-352},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/225/TR99-352.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/225/TR99-352.pdf},
abstract = {
The problems of word sense disambiguation and document indexing for information retrieval
have been extensively studied. It has been observed that indexing using disambiguated
meanings, rather than word stems, should improve information retrieval results.
We present a new corpus-based algorithm for performing word sense disambiguation.
The algorithm does not need to train on many senses of each word; it uses instead
the probability that certain concepts will occur together. That algorithm is then
used to index several corpa of documents. Our indexing algorithm does not generally
outperform the traditional stem-based tf.idf model.
}
comment = {
Undergraduate Honors Thesis. Advisor: Jay Aslam.
}
}
@TechReport{Dartmouth:PCS-TR99-351,
author = {Matthew D. Pearson },
title = {{Fast Out-of-Core Sorting on Parallel Disk Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-351},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/224/TR99-351.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/224/TR99-351.pdf},
abstract = {
This paper discusses our implementation of Rajasekaran's (l,m)-mergesort algorithm
(LMM) for sorting on parallel disks. LMM is asymptotically optimal for large problems
and has the additional advantage of a low constant in its I/O complexity. Our implementation
is written in C using the ViC* I/O API for parallel disk systems. We compare the
performance of LMM to that of the C library function qsort on a DEC Alpha server.
qsort makes a good benchmark because it is fast and performs comparatively well
under demand paging. Since qsort fails when the swap disk fills up, we can only
compare these algorithms on a limited range of inputs. Still, on most out-of-core
problems, our implementation of LMM runs between 1.5 and 1.9 times faster than qsort,
with the gap widening with increasing problem size.
}
comment = {
Undergraduate Honors Thesis. Advisor: Tom Cormen.
}
}
@TechReport{Dartmouth:PCS-TR99-350,
author = {Lauren M. Baptist },
title = {{Two Algorithms for Performing Multidimensional, Multiprocessor, Out-of-Core FFTs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-350},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/223/TR99-350.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/223/TR99-350.pdf},
abstract = {
We show two algorithms for computing multidimensional Fast Fourier Transforms (FFTs)
on a multiprocessor system with distributed memory when problem sizes are so large
that the data do not fit in the memory of the entire system. Instead, data reside
on a parallel disk system and are brought into memory in sections. We use the Parallel
Disk Model for implementation and analysis. The first method is a straightforward
out-of-core variant of a well-known method for in-core, multidimensional FFTs. It
performs 1-dimensional FFT computations on each dimension in turn. This method is
easy to generalize to any number of dimensions, and it also readily permits the
individual dimensions to be of any sizes that are integer powers of~2. The key step
is an out-of-core transpose operation that places the data along each dimension
into contiguous positions on the parallel disk system so that the data for the 1-dimensional
FFTs are contiguous. The second method is an adaptation of another well-known
method for in-core, multidimensional FFTs. This method computes all dimensions simultaneously.
It is more difficult to generalize to arbitrary radices and number of dimensions
in this method than in the first method. Our present implementation is therefore
limited to two dimensions of equal size, that are again integer powers of~2. We
present I/O complexity analyses for both methods as well as empirical results for
a DEC~2100 server and an SGI Origin~2000, each of which has a parallel disk system.
Our results indicate that the methods are comparable in speed in two-dimensions.
}
comment = {
Undergraduate Honors Thesis. Advisor: Tom Cormen.
}
}
@TechReport{Dartmouth:PCS-TR99-349,
author = {David H. Kung },
title = {{Improved Computer Detection and Mapping of Cerebral Oxygenation}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-349},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/222/TR99-349.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/222/TR99-349.pdf},
abstract = {
Near-infrared (NIR) optical image reconstruction that incorporates blood oxygen level
dependant (BOLD) magnetic resonance imaging has the potential to improve both quantifiable
measurement of oxygenation and the spatial resolution involved in such mapping.
My thesis continues some preliminary work in this area through development of an
analytic diffusion parameter estimation algorithm for use with a NIR imaging array
and development of a finite element mesh utility to read a priori BOLD images and
tag them with property elements for NIR image resolution improvement.
}
comment = {
Undergraduate Honors Thesis. Advisors: George Cybenko and Keith Paulsen.
}
}
@TechReport{Dartmouth:PCS-TR99-348,
author = {Marsette A. Vona },
title = {{A Two Dimensional Crystalline Atomic Unit Modular Self-reconfigurable Robot}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-348},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/221/TR99-348.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/221/TR99-348.pdf},
abstract = {
Self-reconfigurable robots are designed so that they can change their external shape
without human intervention. One general way to achieve such functionality is to
build a robot composed of multiple, identical unit modules. If the modules are designed
so that they can be assembled into rigid structures, and so that individual units
within such structures can be relocated within and about the structure, then self-reconfiguration
is possible. We propose the Crystalline Atomic unit modular self-reconfigurable
robot, where each unit is called an Atom. In two dimensions, an Atom is square.
Connectors at the faces of each Atom support structure formation (such structures
are called Crystals). Centrally placed prismatic degrees of freedom give Atoms the
ability to contract their outer side-length by a constant factor. By contracting
and expanding groups of Atoms in a coordinated way, Atoms can relocate within and
about Crystals. Thus Atoms are shown to satisfy the two properties necessary to
function as modules of a self-reconfigurable robot. A powerful software simulator
for Crystalline Atomic robots in two and three dimensions, called xtalsim, is presented.
Xtalsim includes a high-level language interface for specifying reconfigurations,
an engine which expands implicit reconfiguration plans into explicit Crystal state
sequences, and an interactive animator which displays the results in a virtual environment.
An automated planning algorithm for generating reconfigurations, called the Melt-Grow
planner, is described. The Melt-Grow planner is fast (O(n2) for Crystals of n Atoms)
and complete for a fully general subset of Crystals. The Melt-Grow planner is implemented
and interfaced to xtalsim, and an automatically planned reconfiguration is simulated.
Finally, the mechanics, electronics, and software for an Atom implementation are
developed. Two Atoms are constructed and experiments are performed which indicate
that, with some hardware improvements, an interesting self-reconfiguration could
be demonstrated by a group of Atoms.
}
comment = {
Undergraduate Honors Thesis. Advisor: Daniela Rus.
}
}
@TechReport{Dartmouth:PCS-TR99-347,
author = {April M. Rasala },
title = {{Existence Theorems for Scheduling to Meet Two Objectives}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-347},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/220/TR99-347.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/220/TR99-347.pdf},
abstract = {
We will look at the existence of schedules which are simultaneously near-optimal
for two criteria. First, we will present some techniques for proving existence theorems,
in a very general setting, for bicriterion scheduling problems. We will then use
these techniques to prove existence theorems for a large class of problems. We will
consider the relationship between objective functions based on completion time,
flow time, lateness and the number of on-time jobs. We will also present negative
results first for the problem of simultaneously minimizing the maximum flow time
and average weighted flow time and second for minimizing the maximum flow time and
simultaneously maximizing the number of on-time jobs. In some cases we will also
present lower bounds and algorithms that approach our bicriterion existence theorems.
Finally we will improve upon our general existence results in one more specific
environment.
}
comment = {
Undergraduate Honors Thesis. Advisor: Cliff Stein.
}
}
@TechReport{Dartmouth:PCS-TR99-346,
author = {James D. Chalfant },
title = {{Parallel DaSSF Discrete-Event Simulation without Shared Memory}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-346},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/219/TR99-346.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/219/TR99-346.pdf},
abstract = {
The Dartmouth implementation of the Scalable Simulation Framework (DaSSF) is a discrete-event
simulator used primarily in the simulation of networks. It achieves high performance
through parallel processing. DaSSF 1.22 requires shared memory between all processors
in order to operate. This limits the number of processors available and the hardware
platforms that can exploit parallelism. We are interested in extending parallel
DaSSF operation to architectures without shared memory. We explore the requirements
of this by implementing parallel DaSSF using MPI as the sole form of interaction
between processors. The approaches used to achieve this can be abstracted and applied
to the current version of DaSSF. This would allow parallel simulation using shared
memory by processors within a single machine, and also at a higher level between
separate machines using distributed memory.
}
comment = {
Undergraduate Honors Thesis. Advisor: David Nicol.
}
}
@TechReport{Dartmouth:PCS-TR99-345,
author = {Jonathan Bredin and David Kotz and Daniela Rus },
title = {{Mobile-Agent Planning in a Market-Oriented Environment}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-345},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/218/TR99-345.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/218/TR99-345.pdf},
abstract = {
We propose a method for increasing incentives for sites to host arbitrary mobile
agents in which mobile agents purchase their computing needs from host sites. We
present a scalable market-based CPU allocation policy and an on-line algorithm that
plans a mobile agent's expenditure over a multihop ordered itinerary. The algorithm
chooses a set of sites at which to execute and computational priorities at each
site to minimize execution time while preserving a prespecified budget constraint.
We present simulation results of our algorithm to show that our allocation policy
and planning algorithm scale well as more agents are added to the system.
}
comment = {
See related papers.
}
}
@TechReport{Dartmouth:PCS-TR99-344,
author = {Neal E. Young },
title = {{Greedy Approximation Algorithms for K-Medians by Randomized Rounding}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR99-344},
year = {1999},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/217/TR99-344.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/217/TR99-344.pdf},
abstract = {
We give an improved approximation algorithm for the general k-medians problem. Given
any epsilon>0, the algorithm finds a solution of total distance at most D(1+epsilon)
using at most k ln(n+n/epsilon) medians (a.k.a. sites), provided some solution of
total distance D using k medians exists. This improves over the best previous bound
(w.r.t. the number of medians) by a factor of Omega(1/epsilon) provided 1/epsilon=n^O(1).
The algorithm is a greedy algorithm, derived using the method of oblivious randomized
rounding. It requires at most k ln(n+n/epsilon) linear-time iterations. We also
derive algorithms for fractional and weighted variants of the problem.
}
}
@TechReport{Dartmouth:PCS-TR98-343,
author = {Jon Howell and David Kotz },
title = {{Snowflake: Spanning administrative domains}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-343},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/216/TR98-343.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/216/TR98-343.pdf},
abstract = {
Many distributed systems provide a ``single-system image'' to their users, so the
user has the illusion that they are using a single system when in fact they are
using many distributed resources. It is a powerful abstraction that helps users
to manage the complexity of using distributed resources. The goal of the Snowflake
project is to discover how single-system images can be made to span administrative
domains. Our current prototype organizes resources in namespaces and distributes
them using Java Remote Method Invocation. Challenging issues include how much flexibility
should be built into the namespace interface, and how transparent the network and
persistent storage should be. We outline future work on making Snowflake administrator-friendly.
}
}
@TechReport{Dartmouth:PCS-TR98-342,
author = {Craig McGray and Daniela Rus },
title = {{Abstractions for Simplifying Planning in Self-Reconfigurable Robotic Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-342},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/215/TR98-342.pdf},
abstract = {
In [KVRM], we described a three-dimensional self-reconfiguring robot module called
the Molecule Robot.
In this paper, we provide a system of abstractions for modules in self-reconfigurable
robotic systems, and show how this system can be used to simplify the motion planning
of the Molecule Robot system.
}
}
@TechReport{Dartmouth:PCS-TR98-341,
author = {Matthew P. Carter },
title = {{Boosting a Simple Weak Learner For Classifying Handwritten Digits}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-341},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/214/TR98-341.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/214/TR98-341.pdf},
abstract = {
A weak PAC learner is one which takes labeled training examples and produces a classifier
which can label test examples more accurately than random guessing. A strong learner
(also known as a PAC learner), on the other hand, is one which takes labeled training
examples and produces a classifier which can label test examples arbitrarily accurately.
Schapire has constructively proved that a strong PAC learner can be derived from
a weak PAC learner. A performance boosting algorithm takes a set of training examples
and a weak PAC learning algorithm and generates a strong PAC learner.
Our research attempts to solve the problem of learning a multi-valued function and
then boosting the performance of this learner.
We implemented the AdaBoost.M2 boosting algorithm. We developed a problem-general
weak learning algorithm, capable of running under AdaBoost.M2, for learning a multi-valued
function of uniform length bit sequences.
We applied our learning algorithms to the problem of classifying handwritten digits.
For training and testing data, we used the MNIST dataset.
Our experiments demonstrate the underlying weak learner's ability to achieve a fairly
low error rate on the testing data, as well as the boosting algorithm's ability
to reduce the error rate of the weak learner.
}
comment = {
Senior Honors Thesis. Advisor: Jay Aslam.
}
}
@TechReport{Dartmouth:PCS-TR98-340,
author = {Jon Howell and Mark Montague },
title = {{Hey, You Got Your Language In My Operating System!}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-340},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/213/TR98-340.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/213/TR98-340.pdf},
abstract = {
Several projects in the operating systems research community suggest a trend of convergence
among features once divided between operating systems and languages. We describe
how partial evaluation and transformational programming systems apply to this trend
by providing a general framework for application support, from compilation to run-time
services. We contend that the community will no longer think of implementing a static
collection of services and calling it an operating system; instead, this general
framework will allow applications to be flexibly configured, and the ``operating
system'' will simply be the application support that is supplied at run-time.
}
}
@TechReport{Dartmouth:PCS-TR98-339,
author = {Peter N. DeSantis },
title = {{Avoiding Conflicts Dynamically in Direct Mapped Caches with Minimal Hardware Support}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-339},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/212/TR98-339.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/212/TR98-339.pdf},
abstract = {
The memory system is often the weakest link in the performance of today's computers.
Cache design has received increasing attention in recent years as increases in CPU
performance continues to outpace decreases in memory latency. Bershad et al. proposed
a hardware modification called the Cache Miss Lookaside buffer which attempts to
dynamically identify data which is conflicting in the cache and remap pages to avoid
future conflicts. In a follow-up paper, Bershad et al. tried to modify this idea
to work with standard hardware but had less success than with their dedicated hardware.
In this thesis, we focus on a modification of these ideas, using less complicated
hardware and focusing more on sampling policies. The hardware support is reduced
to a buffer of recent cache misses and a cache miss counter. Because determination
of remapping candidates is moved to software, sampling policies are studied to reduce
overhead which will most likely fall on the OS. Our results show that sampling can
be highly effective in identifying conflicts that should be remapped. Finally, we
show that the theoretical performance of such a system can compare favorably with
more costly higher associativity caches.
}
comment = {
Senior Honors Thesis. Advisor: Tom Cormen.
}
}
@TechReport{Dartmouth:PCS-TR98-338,
author = {Michael H. Pryor },
title = {{The Effects of Singular Value Decomposition on Collaborative Filtering}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-338},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/211/TR98-338.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/211/TR98-338.pdf},
abstract = {
As the information on the web increases exponentially, so do the efforts to automatically
filter out useless content and to search for interesting content. Through both explicit
and implicit actions, users define where their interests lie. Recent efforts have
tried to group similar users together in order to better use this data to provide
the best overall filtering capabilities to everyone. This thesis discusses ways
in which linear algebra, specifically the singular value decomposition, can be used
to augment these filtering capabilities to provide better user feedback. The goal
is to modify the way users are compared with one another, so that we can more efficiently
predict similar users. Using data collected from the PhDs.org website, we tested
our hypothesis on both explicit web page ratings and implicit visits data.
}
comment = {
Senior Honors Thesis. Advisor: Jay Aslam and Geoff Davis.
}
}
@TechReport{Dartmouth:PCS-TR98-337,
author = {Ron Oldfield and David Kotz },
title = {{Applications of Parallel I/O}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-337},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/210/TR98-337.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/210/TR98-337.pdf},
abstract = {
Scientific applications are increasingly being implemented on massively parallel
supercomputers. Many of these applications have intense I/O demands, as well as
massive computational requirements. This paper is essentially an annotated bibliography
of papers and other sources of information about scientific applications using parallel
I/O. It will be updated periodically.
}
comment = {
Supplement to PCS-TR96-297.
}
}
@TechReport{Dartmouth:PCS-TR98-336,
author = {Christine J. Alvarado },
title = {{Distributed Route Planning Using Partial Map Building}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-336},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/209/TR98-336.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/209/TR98-336.pdf},
abstract = {
Our goal is to manipulate and guide an object across an unknown environment toward
a goal in a known location in space. Our tools include a system of manipulation
robots, which are "blind" and one mobile scout robot who relies on a series of sonar
sensors for information about the environment. Previous solutions to this problem
have taken a simultaneous guiding and manipulating approach, moving the whole system
under the scout's guidance. My approach, however, presents a separate scouting algorithm
that can return a series of coordinates through which the manipulation system can
safely pass to reach the goal in a static environment. This new approach produces
more optimal paths to the goal, as well as evading the concern of what actions to
take should the entire system reach a dead end. In this paper I will present both
the algorithm and the experimental results I obtained when I built the scouting
system.
}
comment = {
Senior Honors Thesis. Advisor: Daniela Rus. Source code available by
ftp.
}
}
@TechReport{Dartmouth:PCS-TR98-335,
author = {Charles B. Owen },
title = {{Multiple Media Correlation: Theory and Applications}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-335},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/208/TR98-335.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/208/TR98-335.pdf},
abstract = {
This thesis introduces multiple media correlation, a new technology for the automatic
alignment of multiple media objects such as text, audio, and video. This research
began with the question: what can be learned when multiple multimedia components
are analyzed simultaneously? Most ongoing research in computational multimedia has
focused on queries, indexing, and retrieval within a single media type. Video is
compressed and searched independently of audio, text is indexed without regard to
temporal relationships it may have to other media data.
Multiple media correlation provides a framework for locating and exploiting correlations
between multiple, potentially heterogeneous, media streams. The goal is computed
synchronization, the determination of temporal and spatial alignments that optimize
a correlation function and indicate commonality and synchronization between media
objects. The model also provides a basis for comparison of media in unrelated domains.
There are many real-world applications for this technology, including speaker localization,
musical score alignment, and degraded media realignment. Two applications, text-to-speech
alignment and parallel text alignment, are described in detail with experimental
validation. Text-to-speech alignment computes the alignment between a textual transcript
and speech-based audio. The presented solutions are effective for a wide variety
of content and are useful not only for retrieval of content, but in support of automatic
captioning of movies and video. Parallel text alignment provides a tool for the
comparison of alternative translations of the same document that is particularly
useful to the classics scholar interested in comparing translation techniques or
styles.
The results presented in this thesis include (a) new media models more useful in
analysis applications, (b) a theoretical model for multiple media correlation, (c)
two practical application solutions that have wide-spread applicability, and (d)
Xtrieve, a multimedia database retrieval system that demonstrates this new technology
and demonstrates application of multiple media correlation to information retrieval.
This thesis demonstrates that computed alignment of media objects is practical
and can provide immediate solutions to many information retrieval and content presentation
problems. It also introduces a new area for research in media data analysis.
}
comment = {
Ph.D dissertation.
}
}
@TechReport{Dartmouth:PCS-TR98-334,
author = {Jack Pien },
title = {{C Compiler Targeting the Java Virtual Machine}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-334},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/207/TR98-334.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/207/TR98-334.pdf},
abstract = {
One of the major drawbacks in the field of computer software development has been
the inability for applications to compile once and execute across many different
platforms. With the emergence of the Internet and the networking of many different
platforms, the Java programming language and the Java Platform was created by Sun
Microsystems to address this "Write Once, Run Anywhere" problem. What sets a compiled
Java program apart from programs compiled from other high level languages is the
ability of a Java Virtual Machine to execute the compiled Java program on any platform,
as long as the Java Virtual Machine is running on top of that platform. Java's cross
platform capabilities can be extended to other high level languages such as C. The
main objective of our project is to implement a compiler targeting the Java Platform
for a subset of the C language. This will allow code written in that subset of C
to be compiled into Java Virtual Machine instructions, also known as JVM bytecode,
which can then be executed on a Java Virtual Machine running on any platform. The
reader is assumed to be intimately familiar with compiler construction, the use
of the flex scanner generator, the use of the GNU bison parser generator, and the
structure and implementation of the Java Virtual Machine.
}
comment = {
Senior Honors Thesis. Advisor: Jay Aslam.
}
}
@TechReport{Dartmouth:PCS-TR98-333,
author = {Christopher S. Leon },
title = {{An Implementation of External-Memory Depth-First Search}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-333},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/206/TR98-333.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/206/TR98-333.pdf},
abstract = {
In many different areas of computing, problems can arise which are too large to fit
in main memory. For these problems, the I/O cost of moving data between main memory
and secondary storage (for example, disks) becomes a significant bottleneck affecting
the performance of the program. Since most algorithms do not take into account the
size of main memory, new algorithms have been developed to optimize the number of
I/O's performed. This paper details the implementation of one such algorithm, for
external-memory depth-first search. Depth-first search is a basic tool for solving
many problems in graph theory, and since graph theory is applicable for many large
computational problems, it is important to make sure that such a basic tool is designed
to avoid the bottleneck of main memory to secondary storage I/O's. The algorithm
whose implementation is described in this paper is sketched out in an extended abstract
by Chiang et al. We attempt to improve the given algorithm by minimizing I/O's performed,
and to extend the algorithm by finding disjoint trees, and by classifying all the
edges in the problem.
}
comment = {
Senior Honors Thesis. Advisor: Tom Cormen
}
}
@TechReport{Dartmouth:PCS-TR98-332,
author = {Michael G. Ross },
title = {{Multiscouting: Guiding distributed manipulation with multiple mobile sensors}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-332},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/205/TR98-332.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/205/TR98-332.pdf},
abstract = {
This thesis investigates the use of multiple mobile sensors to guide the motion of
a distributed manipulation system. In our system, multiple robots cooperatively
place a large object at a goal in a dynamic, unstructured, unmapped environment.
We take the system developed in [Rus, Kabir, Kotay, Soutter 1996], which employs
a single mobile sensor for navigational tasks, and extend it to allow the use of
multiple mobile sensors. This allows the system to perform successful manipulations
in a larger class of spaces than was possible in the single scout model. We focus
on the development of a negotiation protocol that enables multiple scouts to cooperatively
plan system motion. This algorithm enhances the previous' system's scalability and
adds greater fault-tolerance. Two alternate algorithms for cooperation: a modification
of negotiation and a bidding protocol, are also discussed. Finally, an implementation
of the negotiation protocol is described and experimental data produced by the implementation
is analyzed.
}
comment = {
Senior Honors Thesis. Advisor: Daniela Rus. Source code available by
ftp
}
}
@TechReport{Dartmouth:PCS-TR98-331,
author = {Jonathan Bredin and David Kotz and Daniela Rus },
title = {{Utility Driven Mobile-Agent Scheduling}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-331},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/204/TR98-331.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/204/TR98-331.pdf},
abstract = {
We investigate the possibility of using markets to regulate mobile agents, computer
programs that are capable of migrating from one machine to another. Market participation
requires quantitative information about resource consumption to define demand and
calculate utility.
We create a formal utility model to derive user-demand functions, allowing agents
to efficiently plan expenditure and deal with price fluctuations. By quantifying
demand and utility, resource owners can precisely set a value for a good. We simulate
our model in a mobile agent scheduling environment and show how prices fluctuate,
compounding uncertainty in an agent's plans. To solve this problem, we propose that
resource owners sell options to allow agents to trade away their risk.
}
comment = {
Original version in May 1998; revised October 3, 1998. See related
papers.
}
}
@TechReport{Dartmouth:PCS-TR98-330,
author = {Jon Howell },
title = {{Straightforward Java Persistence Through Checkpointing}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-330},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/203/TR98-330.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/203/TR98-330.pdf},
abstract = {
Several techniques have been proposed for adding persistence to the Java language
environment. This paper describes a scheme based on checkpointing the Java Virtual
Machine, and compares the scheme to other techniques. Checkpointing offers two unique
advantages: first, the implementation is independent of the JVM implementation,
and therefore survives JVM updates; second, because checkpointing saves and restores
execution state, even threads become persistent entities.
}
comment = {
Superceded by a conference paper available at
http://www.cs.dartmouth.edu/~jonh/research/
}
}
@TechReport{Dartmouth:PCS-TR98-329,
author = {Matthew P. Carter and David Kotz },
title = {{An Implementation of the Vesta Parallel File System API on the Galley Parallel File System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-329},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/202/TR98-329.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/202/TR98-329.pdf},
abstract = {
To demonstrate the flexibility of the Galley parallel file system and to analyze
the efficiency and flexibility of the Vesta parallel file system interface, we implemented
Vesta's application-programming interface on top of Galley. We implemented the Vesta
interface using Galley's file-access methods, whose design arose from extensive
testing and characterization of the I/O requirements of scientific applications
for high-performance multiprocessors. We used a parallel CPU, parallel I/O, out-of-core
matrix-multiplication application to test the Vesta interface in both its ability
to specify data access patterns and in its run-time efficiency. In spite of its
powerful ability to specify the distribution of regular, non-overlapping data access
patterns across disks, we found that the Vesta interface has some significant limitations.
We discuss these limitations in detail in the paper, along with the performance
results.
}
}
@TechReport{Dartmouth:PCS-TR98-328,
author = {Cem Paya },
title = {{A framework for World Wide Web client-authentication protocols}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-328},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/201/TR98-328.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/201/TR98-328.pdf},
abstract = {
Existing client-authentication protocols deployed on the World Wide Web today are
based on conventional distributed systems and fail to address the problems specific
to the application domain. Some of the protocols restrict the mobility of the client
by equating user identity to a machine or network address, others depend on sound
password management strategies, and yet others compromise the privacy of the user
by transmitting personal information for authentication. We introduce a new framework
for client-authentication by separating two goals that current protocols achieve
simultaneously:
1. Maintain persistent sense of identity across different sessions.
2. Prove facts about the user to the site.
These problems are independent, in the sense that any protocol for solving the first
problem can be combined with any protocol for solving the second. Separation of
the two purposes opens up the possibility of designing systems which balance two
conflicting goals, authentication and anonymity. We propose a solution to the first
problem, based on the Digital Signature Standard. The implications of this framework
from the point of view of user privacy are examined. The paper is concluded with
suggestions for integrating the proposed scheme into the existing WWW architecture.
}
comment = {
Senior Honors Thesis. Advisor: Robert H. Morris, Sr.
}
}
@TechReport{Dartmouth:PCS-TR98-327,
author = {Robert S. Gray },
title = {{Agent Tcl: A flexible and secure mobile-agent system}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-327},
year = {1998},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/200/TR98-327.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/200/TR98-327.pdf},
abstract = {
A mobile agent is an autonomous program that can migrate under its own control from
machine to machine in a heterogeneous network. In other words, the program can suspend
its execution at an arbitrary point, transport itself to another machine, and then
resume execution from the point of suspension. Mobile agents have the potential
to provide a {em single, general framework} in which a wide range of distributed
applications can be implemented efficiently and easily. Several challenges must
be faced, however, most notably reducing migration overhead, protecting a machine
from malicious agents (and an agent from malicious machines), and insulating the
agent against network and machine failures. Agent Tcl is a mobile-agent system under
development at Dartmouth College that has evolved from a Tcl-only system into a
multiple-language system that currently supports Tcl, Java, and Scheme. In this
thesis, we examine the motivation behind mobile agents, describe the base Agent
Tcl system and its security mechanisms for protecting a machine against malicious
agents, and analyze the system's current performance. Finally, we discuss the security,
fault-tolerance and performance enhancements that will be necessary for Agent Tcl
and mobile agents in general to realize their full potential.
}
comment = {
Ph.D. Thesis.
Related papers.
}
}
@TechReport{Dartmouth:PCS-TR98-311,
author = {Jonathan Bredin and David Kotz and Daniela Rus },
title = {{Utility Driven Mobile-Agent Scheduling}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR98-311},
year = {0005},
month = {January},
comment = {
This technical report number is incorrect. The correct number for this report is
TR98-331.
TR98-331 web page. See related
papers.
}
}
@TechReport{Dartmouth:PCS-TR97-326,
author = {Jonathan Bredin and David Kotz and Daniela Rus },
title = {{Market-based Resource Control for Mobile Agents}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-326},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/198/TR97-326.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/198/TR97-326.pdf},
abstract = {
Mobile agents are programs that can migrate from machine to machine in a heterogeneous,
partially disconnected network. As mobile agents move across a network, they consume
resources. We discuss a system for controlling the activities of mobile agents that
uses electronic cash, a banking system, and a set of resource managers. We describe
protocols for transactions between agents. We present fixed-pricing and dynamic-pricing
policies for resources. We focus on and analyze the sealed-bid second-price auction
as a mechanism for dynamic pricing.
}
comment = {
A revised version appeared in the conference Autonomous Agents '98. See here.
See related papers.
}
}
@TechReport{Dartmouth:PCS-TR97-325,
author = {Stavros G. Kolliopoulos and Clifford Stein },
title = {{Approximating Disjoint-Path Problems Using Greedy Algorithms and Packing Integer Programs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-325},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/197/TR97-325.pdf},
abstract = {
In the edge(vertex)-disjoint path problem we are given a graph $G$ and a set ${cal
T}$ of connection requests. Every connection request in ${cal T}$ is a vertex pair
$(s_i,t_i),$ $1 leq i leq K.$ The objective is to connect a maximum number of the
pairs via edge(vertex)-disjoint paths. The edge-disjoint path problem can be generalized
to the multiple-source unsplittable flow problem where connection request $i$ has
a demand $rho_i$ and every edge $e$ a capacity $u_e.$ All these problems are NP-hard
and have a multitude of applications in areas such as routing, scheduling and bin
packing.
Given the hardness of the problem, we study polynomial-time approximation algorithms.
In this context, a $rho$-approximation algorithm is able to route at least a $1/rho$
fraction of the connection requests. Although the edge- and vertex-disjoint path
problems, and more recently the unsplittable flow generalization, have been extensively
studied, they remain notoriously hard to approximate with a bounded performance
guarantee. For example, even for the simple edge-disjoint path problem, no $o(sqrt{|E|})$-approximation
algorithm is known. Moreover some of the best existing approximation ratios are
obtained through sophisticated and non-standard randomized rounding schemes.
In this paper we introduce techniques which yield algorithms for a wide range of
disjoint-path and unsplittable flow problems. For the general unsplittable flow
problem, even with weights on the commodities, our techniques lead to the first
approximation algorithm and obtain an approximation ratio that matches, to within
logarithmic factors, the $O(sqrt{|E|})$ approximation ratio for the simple edge-disjoint
path problem. In addition to this result and to improved bounds for several disjoint-path
problems, our techniques simplify and unify the derivation of many existing approximation
results.
We use two basic techniques. First, we propose simple greedy algorithms for edge-
and vertex-disjoint paths and second, we propose the use of a framework based on
packing integer programs for more general problems such as unsplittable flow. A
packing integer program is of the form maximize $c^{T}cdot x,$ subject to $Ax leq
b,$ $A,b,c geq 0.$ As part of our tools we develop improved approximation algorithms
for a class of packing integer programs, a result that we believe is of independent
interest.
}
comment = {
Revised November 1997.
}
}
@TechReport{Dartmouth:PCS-TR97-324,
author = {J. Aslam and K. Pelekhov and Daniela Rus },
title = {{Computing Dense Clusters On-line for Information Organization}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-324},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/196/TR97-324.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/196/TR97-324.pdf},
abstract = {
We present and analyze the off-line star algorithm for clustering static information
systems and the on-line star algorithm for clustering dynamic information systems.
These algorithms partition a document collection into a number of clusters that
is naturally induced by the collection. We show a lower bound on the accuracy of
the clusters produced by these algorithms. We use the random graph model to show
that both star algorithms produce correct clusters in time Theta(V + E). Finally,
we provide data from extensive experiments.
}
comment = {
Submitted to the 1998 SIGIR Conference.
}
}
@TechReport{Dartmouth:PCS-TR97-323,
author = {Alex Colvin and Thomas H. Cormen },
title = {{ViC*: A Compiler for Virtual-Memory C*}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-323},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/195/TR97-323.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/195/TR97-323.pdf},
abstract = {
This paper describes the functionality of ViC*, a compiler for a variant of the data-parallel
language C* with support for out-of-core data. The compiler translates C* programs
with shapes declared outofcore, which describe parallel data stored on disk. The
compiler output is a SPMD-style program in standard C with I/O and library calls
added to efficiently access out-of-core parallel data. The ViC* compiler also applies
several program transformations to improve out-of-core data layout and access.
}
comment = {
Revised version appeared in the Proceedings of the Third International Workshop on
High-Level Parallel Programming Models and Supportive Environments (HIPS '98), March
1998, pages 23-33.
}
}
@TechReport{Dartmouth:PCS-TR97-322,
author = {Thomas H. Cormen },
title = {{Determining an Out-of-Core FFT Decomposition Strategy for Parallel Disks by Dynamic Programming}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-322},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/194/TR97-322.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/194/TR97-322.pdf},
abstract = {
We present an out-of-core FFT algorithm based on the in-core FFT method developed
by Swarztrauber. Our algorithm uses a recursive divide-and-conquer strategy, and
each stage in the recursion presents several possibilities for how to split the
problem into subproblems. We give a recurrence for the algorithm's I/O complexity
on the Parallel Disk Model and show how to use dynamic programming to determine
optimal splits at each recursive stage. The algorithm to determine the optimal splits
takes only Theta(lg^2 N) time for an N-point FFT, and it is practical. The out-of-core
FFT algorithm itself takes considerably longer.
}
comment = {
Also appeared in Proceedings of the Workshop on Algorithms for Parallel Machines,
1996-97 Special Year on Mathematics of High Performance Computing, Institute for
Mathematics and Its Applications, University of Minnesota, Minneapolis, September
1996.
}
}
@TechReport{Dartmouth:PCS-TR97-321,
author = {Charles B. Owen and Fillia Makedon },
title = {{Multiple Media Stream Data Analysis: Theory and Applications (Extended version)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-321},
year = {2010},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/193/TR97-321.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/193/TR97-321.pdf},
abstract = {
This paper presents a new model for multiple media stream data analysis as well as
descriptions of some applications of this model in development at Dartmouth College.
This model formalizes the exploitation of correlations between multiple, potentially
heterogeneous, media streams in support of numerous application areas. The goal
of the technique is to determine temporal and spatial alignments which optimize
a correlation function and indicate commonality and synchronization between media
streams. It also provides a framework for comparison of media in unrelated domains.
Applications such as text-to-speech alignment, functional magnetic resonance imaging,
speaker localization, and degraded media realignment are described.
}
comment = {
A shorter version of this paper appears in the Proceedings of Gesellschaft fur Klassifikation
e.V., University of Potsdam, Potsdam, Germany, March 12-14, 1997
}
}
@TechReport{Dartmouth:PCS-TR97-320,
author = {Neal E. Young },
title = {{On-Line File Caching}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-320},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/192/TR97-320.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/192/TR97-320.pdf},
abstract = {
Consider the following file caching problem: in response to a sequence of requests
for files, where each file has a specified size and retrieval cost, maintain a cache
of files of total size at most some specified k so as to minimize the total retrieval
cost. Specifically, when a requested file is not in the cache, bring it into the
cache, pay the retrieval cost, and choose files to remove from the cache so that
the total size of files in the cache is at most k. This problem generalizes previous
paging and caching problems by allowing objects of arbitrary size and cost, both
important attributes when caching files for world-wide-web browsers, servers, and
proxies. We give a simple deterministic on-line algorithm that generalizes many
well-known paging and weighted-caching strategies, including least-recently-used,
first-in-first-out, flush-when-full, and the balance algorithm. On any request sequence,
the total cost incurred by the algorithm is at most k/(k-h+1) times the minimum
possible using a cache of size h <= k. For any algorithm satisfying the latter bound,
we show it is also the case that for most choices of k, the retrieval cost is either
insignificant or the competitive ratio is constant. This helps explain why competitive
ratios of many on-line paging algorithms have been typically observed to be constant
in practice.
}
}
@TechReport{Dartmouth:PCS-TR97-319,
author = {J. Aslam and K. Pelekhov and Daniela Rus },
title = {{Generating, Visualizing and Evaluating High Quality Clusters for Information Organization}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-319},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/191/TR97-319.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/191/TR97-319.pdf},
abstract = {
We present and analyze the star clustering algorithm. We discuss an implementation
of this algorithm that supports browsing and document retrieval through information
organization. We define three parameters for evaluating a clustering algorithm to
measure the topic separation and topic aggregation achieved by the algorithm. In
the absence of benchmarks, we present a method for randomly generating clustering
data. Data from our user study shows evidence that the star algorithm is effective
for organizing information.
}
comment = {
Submitted to the 1998 SIGIR Conference.
}
}
@TechReport{Dartmouth:PCS-TR97-318,
author = {Eric Hagen },
title = {{An Information Retrieval System for Performing Hierarchical Document Clustering}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-318},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/190/TR97-318.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/190/TR97-318.pdf},
abstract = {
This thesis presents a system for web-based information retrieval that supports precise
and informative post-query organization (automated document clustering by topic)
to decrease real search time on the part of the user. Most existing Information
Retrieval systems depend on the user to perform intelligent, specific queries with
Boolean operators in order to minimize the set of returned documents. The user essentially
must guess the appropriate keywords before performing the query. Other systems use
a vector space model which is more suitable to performing the document similarity
operations which permit hierarchical clustering of returned documents by topic.
This allows "post query" refinement by the user. The system we propose is a hybrid
beween these two systems, compatibile with the former, while providing the enhanced
document organization permissable by the latter.
}
comment = {
Senior Honors Thesis. Advisor: Javed Aslam.
}
}
@TechReport{Dartmouth:PCS-TR97-317,
author = {Thomas H. Cormen },
title = {{Performing BMMC Permutations Efficiently on Distributed-Memory Multiprocessors with MPI}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-317},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/189/TR97-317.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/189/TR97-317.pdf},
abstract = {
This paper presents an architecture-independent method for performing BMMC permutations
on multiprocessors with distributed memory. All interprocessor communication uses
the MPI function MPI_Sendrecv_replace(). The number of elements and number of processors
must be powers of 2, with at least one element per processor, and there is no inherent
upper bound on the ratio of elements per processor.
Our method transmits only data without transmitting any source or target indices,
which conserves network bandwidth. When data is transmitted, the source and target
processors implicitly agree on each other's identity and the indices of the elements
being transmitted.
A C-callable implementation of our method is available from Netlib. The implementation
allows preprocessing (which incurs a modest cost) to be factored out for multiple
runs of the same permutation, even if on different data. Data may be laid out in
any one of several ways: processor-major, processor-minor, or anything in between.
}
comment = {
Revised version appeared in Algorithmica volume 24, number 3/4, July and August 1999,
pages 349-370.
}
}
@TechReport{Dartmouth:PCS-TR97-316,
author = {Jon Feldman },
title = {{The Complexity Of Clerkship Scheduling}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-316},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/188/TR97-316.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/188/TR97-316.pdf},
abstract = {
Medical students must complete a clerkship program in their fourth year. Individual
students have preferences for the clerkships to which they are assigned. However,
individual hospitals also have capacities on how many students may be assigned to
each clerkship. The problem of scheduling medical students to clerkships is formalized.
The problem is then placed in a theoretical framework, and the most general case
of Clerkship Scheduling is proven NP-hard. A detailed approximation algorithm is
given, and an implementation of this algorithm is discussed and tested.
}
comment = {
Senior Honors Thesis. Advisor: Cliff Stein.
}
}
@TechReport{Dartmouth:PCS-TR97-315,
author = {Simon Holmes a Court },
title = {{Admission Control Policies for Internet File Transfer Protocols}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-315},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/187/TR97-315.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/187/TR97-315.pdf},
abstract = {
Server congestion is a major cause of frustration with the Internet. It is not uncommon
for a server with a new release of popular software to be swamped by many times
more clients than it can possibly handle. Current Internet file transfer protocols,
namely FTP and HTTP, do not have any policy to regulate client admission. In this
thesis we are concerned with server admission policies that will improve clients'
experience with servers under heavy load. Using a purpose-built network simulator,
we compare the prevalent protocols with two new protocols that include policies
taken from processor scheduling.
By applying more intelligent client admission policies it is hoped that the quality
of service on the Internet can be improved.
}
comment = {
Senior Honors Thesis. Advisor: John M. Danskin.
}
}
@TechReport{Dartmouth:PCS-TR97-314,
author = {Ka-Tak Lo },
title = {{KLZ: A Prototype X Protocol Compression System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-314},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/186/TR97-314.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/186/TR97-314.pdf},
abstract = {
One of the most commonly used graphics protocol is the X Protocol, enabling programs
to display graphics images. When running the X Protocol over the network, a lot
of structured data (messages with fields) need to be transmitted. Delays can be
detected by human users when connected through a low-bandwidth network. The solution
is to compress the X protocol. XRemote, a network version of the X Protocol, uses
Dictionary-based compression. In XRemote, strings are recorded in the dictionary.
When a string repeats, its index in the dictionary is transmitted. Higher Bandwidth
X (HBX) uses statistical modeling techniques instead. A context model, which depends
on the nature of the field in a particular type of message and the frequencies of
the values of the field, is associated with each field. XRemote is much faster than
HBX, but HBX achieves better compression than XRemote. The KLZ system is developed
to take advantage of our knowledge about the fields in the XMotionNotify packet
(what X sends when the mouse moves) and fast Dictionary (LZW) compression. In essence,
KLZ reorders and rewrites fields in the XMotionNotify packet so that the fields
will be more easily compressed by the fast LZ coder. My experiments show that KLZ
compresses this packet nearly as well as HBX, and 5 times better than pure LZ. KLZ
is slightly faster than pure LZ, and and 10 times faster than HBX. Since many modems
already implement LZ compression, KLZ could also be used to reorder data before
passing them to the modem with LZ compression for transmission. This reordering
would lead to vastly improved compression almost for free.
}
comment = {
Senior Honors Thesis. Advisor: John M. Danskin.
}
}
@TechReport{Dartmouth:PCS-TR97-313,
author = {Dawn Lawrie },
title = {{Self-Organizing File Cabinet}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR97-313},
year = {1997},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/185/TR97-313.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/185/TR97-313.pdf},
abstract = {
This thesis presents a self-organized file cabinet. This file cabinet uses electronic
information to augment the physical world. By using a scanner to transform documents
into electronic files, the self-organized file cabinet can index the documents on
visual and textual information. The self-organized file cabinet helps the user find
the documents at a later date. The focus of this thesis is on the design and evaluation
of the self-organized file cabinet. User studies show that this tool is natural
to use.
}
comment = {
Senior Honors Thesis. Advisor: Daniela Rus.
The figures are included in a separate appendix (1285KB uncompressed, 167KB compressed). } } @TechReport{Dartmouth:PCS-TR97-312, author = {Sanjay Khanna and David Kotz }, title = {{A Split-Phase Interface for Parallel File Systems}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-312}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/184/TR97-312.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/184/TR97-312.pdf}, abstract = { We describe the effects of a new user-level library for the Galley Parallel File System. This library allows some pre-existing sequential programs to make use of the Galley Parallel File System with minimal modification. It permits programs to efficiently use the parallel file system because the user-level library groups accesses together. We examine the performance of our library, and we show how code needs to be modified to use the library. } } @TechReport{Dartmouth:PCS-TR97-311, author = {Prasad Jayanti and Sanjay Khanna }, title = {{On the Power of Multi-Objects}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-311}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/183/TR97-311.pdf}, abstract = { In the standard ``single-object'' model of shared-memory computing, it is assumed that a process accesses at most one shared object in each of its steps. In this paper, we consider a more powerful variant---the ``multi-object'' model---in which each process may access *any* finite number of shared objects atomically in each of its steps. We present results that relate the synchronization power of a type in the multi-object model to its synchronization power in the single-object model. Although the types fetch&add and swap have the same synchronization power in the single-object model, Afek, Merritt, and Taubenfeld showed that their synchronization powers differ in the multi-object model. We prove that this divergence phenomenon is exhibited {em only/} by types at levels 1 and 2; all higher level types have the same unbounded synchronization power in the multi-object model stated above. This paper identifies all possible relationships between a type's synchronization power in the single-object model and its synchronization power in the multi-object model. } comment = { Appeared in WDAG 1997, Lecture Notes in Computer Science #1320. } } @TechReport{Dartmouth:PCS-TR97-310, author = {Charles B. Owen and Fillia Makedon }, title = {{Multimedia Data Analysis using ImageTcl (Extended version)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-310}, year = {2010}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/182/TR97-310.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/182/TR97-310.pdf}, abstract = { ImageTcl is an new system which provides powerful Tcl/Tk based media scripting capabilities similar to those of the ViewSystem and Rivl in a unique environment that allows rapid prototyping and development of new components in the C++ language. Powerful user tools automate the creation of new components as well as the addition of new data types and file formats. Applications using ImageTcl at the Dartmouth Experimental Visualization Laboratory (DEVLAB) include multiple stream media data analysis, automatic image annotation, and image sequence motion analysis. ImageTcl combines the high speed of compiled languages with the testing and parameterization advantages of scripting languages. } comment = { A shorter version of this paper appears in the Proceedings of Gesellschaft fur Klassifikation e.V., University of Potsdam, Potsdam, Germany, March 12-14, 1997 } } @TechReport{Dartmouth:PCS-TR97-309, author = {Charles B. Owen and Fillia Makedon and Glen Frank and Michael Kenyon }, title = {{ASML: Automatic Site Markup Language 1.03}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-309}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/181/TR97-309.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/181/TR97-309.pdf}, abstract = { Creation of large and complex World Wide Web sites is hampered by the "page at a time" approach of many tools and the programming knowledge and custom software development required for automated solutions. This report describes the development of the Automatic Site Markup Language (ASML). ASML is a new markup language designed to produce large, complicated web sites which can include dynamic content. ASML extends HTML with new, high-level features while still preserving complete compatibility with common browser and server technologies. It has powerful indexing and searching facilities, and enables the automatic translation of document formats. Most importantly, ASML provides HTML-like features at the site level rather than just the page level } } @TechReport{Dartmouth:PCS-TR97-308, author = {Fillia Makedon and James Matthews and Charles B. Owen and Samuel A. Rebelsky }, title = {{An Efficient Scheme for a Distributed Video Retrieval System for Remote Users}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-308}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/180/TR97-308.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/180/TR97-308.pdf}, abstract = { The new era of digital video and multimedia technologies has created the potential for large libraries of digital video. With this new technology come the challenges of creating usable means by which such large and diverse depositories of digital information (digital libraries) can be efficiently queried and accessed so that (a) the response is fast, (b) the communication over the Internet is minimal and (c) the retrieval is characterized by high precision and recall. In this paper we discuss how existing digital video editing tools, together with data compression techniques, can be combined to create a fast, accurate and cost effective video retrieval system for remote users. The traditional approaches employed in text databases, such as keyword searching and volume browsing, are inadequate mechanisms for a video retrieval system for remote users because, (a) they don't apply to video at all, or (b) they are not practical due to the amounts of data involved, or (c) they have insufficient resolution to be useful in a video archive. New techniques must be developed that facilitate the query and selection of digital video. This paper presents one such scheme. } } @TechReport{Dartmouth:PCS-TR97-307, author = {Xiaowen Liu and Charles B. Owen and Fillia Makedon }, title = {{Automatic Video Pause Detection Filter}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-307}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/179/TR97-307.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/179/TR97-307.pdf}, abstract = { Increasing interest in multimedia research has been drawn upon the development of video indexing and content-based image retrieval techniques. In this report, we proposed several pause detection algorithms, which instead of searching for significant visual transitions, the algorithms detect significant pauses in video streams. A realization of the algorithms was implemented using ImageTcl toolkit developed at Dartmouth Experimental Visualization Laboratory. In addition to proposing and studying the effectiveness of the pause detection algorithms, another major goal will be to incorporate our algorithms into ImageTcl and test the stability and applicability of the ImageTcl environment. Priliminary experiments showed relatively good results of our pause detection algorithms. } } @TechReport{Dartmouth:PCS-TR97-306, author = {Melissa Hirschl and David Kotz }, title = {{AGDB: A Debugger for Agent Tcl}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-306}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/178/TR97-306.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/178/TR97-306.pdf}, abstract = { The Agent Tcl language is an extension of Tcl/Tk that supports distributed programming in the form of transportable agents. AGDB is a debugger for the Agent Tcl language. AGDB mixes of traditional and distributed debugging facilities. Traditional debugging features include breakpoints (line-specific, conditional, and once-only), watch conditions and variables, and interrupts. Distributed-debugging features address issues inherent in distributed programming such as migration and communication. These capabilities make debugging distributed programs difficult because they add complexities like race conditions to the set of problems a program can encounter. This paper discusses how AGDB uses distributed debugging features to debug agents. } } @TechReport{Dartmouth:PCS-TR97-305, author = {Daniela Rus and P. deSantis }, title = {{The Self-Organizing Desk}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-305}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/177/TR97-305.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/177/TR97-305.pdf}, abstract = { The self-organizing desk is a system that enhances a physical desk-top with electronic information. It can remember, organize, update, and manipulate the information contained in the documents on a desk. The system consists of a simple robot eye that can survey the desk, a module for smart extraction of information from the images taken by the robot, a module for representing this information in multiple views, and a module that allows a user to interact with this information. } comment = { In Proceedings of the 1997 International Joint Conference on Artificial Intelligence, Nagoya, Japan, August 1997. } } @TechReport{Dartmouth:PCS-TR97-304, author = {David M. Nicol and Gianfranco F. Ciardo }, title = {{Automated Parallelization of Discrete State-space Generation}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-304}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/176/TR97-304.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/176/TR97-304.pdf}, abstract = { We consider the problem of generating a large state-space in a distributed fashion. Unlike previously proposed solutions that partition the set of reachable states according to a hashing function provided by the user, we explore heuristic methods that completely automate the process. The first step is an initial random walk through the state space to initialize a search tree, duplicated in each processor. Then, the reachability graph is built in a distributed way, using the search tree to assign each newly found state to classes assigned to the available processors. Furthermore, we explore two remapping criteria that attempt to balance memory usage or future workload, respectively. We show how the cost of computing the global snapshot required for remapping will scale up for system sizes in the foreseeable future. An extensive set of results is presented to support our conclusions that remapping is extremely beneficial. } comment = { Submitted to Journal of Parallel and Distributed Computing. } } @TechReport{Dartmouth:PCS-TR97-303, author = {Thomas H. Cormen and Jake Wegmann and David M. Nicol }, title = {{Multiprocessor Out-of-Core FFTs with Distributed Memory and Parallel Disks}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR97-303}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/175/TR97-303.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/175/TR97-303.pdf}, abstract = { This paper extends an earlier out-of-core Fast Fourier Transform (FFT) method for a uniprocessor with the Parallel Disk Model (PDM) to use multiple processors. Four out-of-core multiprocessor methods are examined. Operationally, these methods differ in the size of "mini-butterfly" computed in memory and how the data are organized on the disks and in the distributed memory of the multiprocessor. The methods also perform differing amounts of I/O and communication. Two of them have the remarkable property that even though they are computing the FFT on a multiprocessor, all interprocessor communication occurs outside the mini-butterfly computations. Performance results on a small workstation cluster indicate that except for unusual combinations of problem size and memory size, the methods that do not perform interprocessor communication during the mini-butterfly computations require approximately 86% of the time of those that do. Moreover, the faster methods are much easier to implement. } comment = { Revised version appeared in IOPADS '97. } } @TechReport{Dartmouth:PCS-TR96-302, author = {Neal E. Young }, title = {{Cross-input Amortization Captures the Diffuse Adversary}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-302}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/174/TR96-302.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/174/TR96-302.pdf}, abstract = { Koutsoupias and Papadimitriou recently raised the question of how well deterministic on-line paging algorithms can do against a certain class of adversarially biased random inputs. Such an input is given in an on-line fashion; the adversary determines the next request probabilistically, subject to the constraint that no page may be requested with probability more than a fixed $epsilon>0$. In this paper, we answer their question by estimating, within a factor of two, the optimal competitive ratio of any deterministic on-line strategy against this adversary. We further analyze randomized on-line strategies, obtaining upper and lower bounds within a factor of two. These estimates reveal the qualitative changes as $epsilon$ ranges continuously from 1 (the standard model) towards 0 (a severely handicapped adversary). The key to our upper bounds is a novel charging scheme that is appropriate for adversarially biased random inputs. The scheme adjusts the costs of each input so that the expected cost of a random input is unchanged, but working with adjusted costs, we can obtain worst-case bounds on a per-input basis. This lets us use worst-case analysis techniques while still thinking of some of the costs as expected costs. } } @TechReport{Dartmouth:PCS-TR96-301, author = {Charles B. Owen and Fillia Makedon }, title = {{High Quality Alias Free Image Rotation}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-301}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/173/TR96-301.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/173/TR96-301.pdf}, abstract = { This paper presents new algorithms for the rotation of images. The primary design criteria for these algorithms is very high quality. Common methods for image rotation, including convolutional and separable approaches, are examined and shown to exhibit significant high frequency aliasing problems. A new resampling filter design methodology is presented which minimizes the problem for conventional convolution-based image rotation. The paper also presents a new separable image rotation algorithm which exhibits improved performance in term of reduction in artifacts and an efficient $O(N^{2} log N)$ running time. } comment = { Appears in Proceedings of 30th Asilomar Conference on Signals, Systems and Computers, Pacific Grove, CA, November 2-6, 1996. } } @TechReport{Dartmouth:PCS-TR96-300, author = {Nils Nieuwejaar }, title = {{Galley: A New Parallel File System for Parallel Applications}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-300}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/172/TR96-300.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/172/TR96-300.pdf}, abstract = { Most current multiprocessor file systems are designed to use multiple disks in parallel, using the high aggregate bandwidth to meet the growing I/O requirements of parallel scientific applications. Most multiprocessor file systems provide applications with a conventional Unix-like interface, allowing the application to access those multiple disks transparently. This interface conceals the parallelism within the file system, increasing the ease of programmability, but making it difficult or impossible for sophisticated application and library programmers to use knowledge about their I/O to exploit that parallelism. In addition to providing an insufficient interface, most current multiprocessor file systems are optimized for a different workload than they are being asked to support. In this work we examine current multiprocessor file systems, as well as how those file systems are used by scientific applications. Contrary to the expectations of the designers of current parallel file systems, the workloads on those systems are dominated by requests to read and write small pieces of data. Furthermore, rather than being accessed sequentially and contiguously, as in uniprocessor and supercomputer workloads, files in multiprocessor file systems are accessed in regular, structured, but non-contiguous patterns. Based on our observations of multiprocessor workloads, we have designed Galley, a new parallel file system that is intended to efficiently support realistic scientific multiprocessor workloads. In this work, we introduce Galley and discuss its design and implementation. We describe Galley's new three-dimensional file structure and discuss how that structure can be used by parallel applications to achieve higher performance. We introduce several new data-access interfaces, which allow applications to explicitly describe the regular access patterns we found to be common in parallel file system workloads. We show how these new interfaces allow parallel applications to achieve tremendous increases in I/O performance. Finally, we discuss how Galley's new file structure and data-access interfaces can be useful in practice. } } @TechReport{Dartmouth:PCS-TR96-299, author = {Brian J. Premore and David M. Nicol and Xiaowen Liu }, title = {{A Critique of the Telecommunications Description Language (TeD)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-299}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/171/TR96-299.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/171/TR96-299.pdf}, abstract = { TeD is an object-oriented description language designed to facilitate the modeling of large scale telecommunication networks, with simulation on parallel and distributed platforms. TeD models are mapped to the Georgia Tech Time Warp engine (GTW) for execution. In this paper we outline the features of TeD, pointing out its strengths and identifying characteristics that gave us trouble as we used TeD to model detailed networks. Our issues are motivated specifically by a model of TCP and a model of multicast resource allocation. Our intention is to illustrate by example what TeD can do, and characteristics that a potential TeD user should be aware of. } } @TechReport{Dartmouth:PCS-TR96-298, author = {David M. Nicol and Xiaowen Liu }, title = {{The Dark Side of Risk (What your mother never told you about Time Warp)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-298}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/170/TR96-298.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/170/TR96-298.pdf}, abstract = { This paper is a reminder of the danger of allowing ``risk'' when synchronizing a parallel discrete-event simulation: a simulation code that runs correctly on a serial machine may, when run in parallel, fail catastrophically. This can happen when Time Warp presents an ``inconsistent'' message to an LP, a message that makes absolutely no sense given the LP's state. Failure may result if the simulation modeler did not anticipate the possibility of this inconsistency. While the problem is not new, there has been little discussion of how to deal with it; furthermore the problem may not be evident to new users or potential users of parallel simulation. This paper shows how the problem may occur, and the damage it may cause. We show how one may eliminate inconsistencies due to lagging rollbacks and stale state, but then show that so long as risk is allowed it is still possible for an LP to be placed in a state that is inconsistent with model semantics, again making it vulnerable to failure. We finally show how simulation code can be tested to ensure safe execution under a risk-free protocol. Whether risky or risk-free, we conclude that under current practice the development of correct and safe parallel simulation code is not transparent to the modeler; certain protections must be included in model code or model testing that are not rigorously necessary if the simulation were executed only serially. } } @TechReport{Dartmouth:PCS-TR96-297, author = {David Kotz }, title = {{Applications of Parallel I/O}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-297}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/169/TR96-297.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/169/TR96-297.pdf}, abstract = { Scientific applications are increasingly being implemented on massively parallel supercomputers. Many of these applications have intense I/O demands, as well as massive computational requirements. This paper is essentially an annotated bibliography of papers and other sources of information about scientific applications using parallel I/O. It will be updated periodically. } comment = { A supplement of this report appeared as TR98-337. The bibliography for this technical report is also available in BibTeX and HTML, with links to many of the cited papers. } } @TechReport{Dartmouth:PCS-TR96-296, author = {David Kotz }, title = {{Tuning STARFISH}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-296}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/168/TR96-296.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/168/TR96-296.pdf}, abstract = { STARFISH is a parallel file-system simulator we built for our research into the concept of disk-directed I/O. In this report, we detail steps taken to tune the file systems supported by STARFISH, which include a traditional parallel file system (with caching) and a disk-directed I/O system. In particular, we now support two-phase I/O, use smarter disk scheduling, increased the maximum number of outstanding requests that a compute processor may make to each disk, and added gather/scatter block transfer. We also present results of the experiments driving the tuning effort. } } @TechReport{Dartmouth:PCS-TR96-295, author = {Clifford Stein and Joel Wein }, title = {{On the Existence of Schedules that are Near-Optimal for both Makespan and Total Weighted Completion time}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-295}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/167/TR96-295.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/167/TR96-295.pdf}, abstract = { We give a simple proof that, for any instance of a very general class of scheduling problems, there exists a schedule of makespan at most twice that of the optimal possible and of total weighted completion time at most twice that of the optimal possible. We then refine the analysis, yielding variants of this theorem with improved constants, and give some algorithmic consequences of the technique. } } @TechReport{Dartmouth:PCS-TR96-294, author = {Thomas H. Cormen and David M. Nicol }, title = {{Performing Out-of-Core FFTs on Parallel Disk Systems}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-294}, year = {1997}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/166/TR96-294.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/166/TR96-294.pdf}, abstract = { The Fast Fourier Transform (FFT) plays a key role in many areas of computational science and engineering. Although most one-dimensional FFT problems can be solved entirely in main memory, some important classes of applications require out-of-core techniques. For these, use of parallel I/O systems can improve performance considerably. This paper shows how to perform one-dimensional FFTs using a parallel disk system with independent disk accesses. We present both analytical and experimental results for performing out-of-core FFTs in two ways: using traditional virtual memory with demand paging, and using a provably asymptotically optimal algorithm for the Parallel Disk Model (PDM) of Vitter and Shriver. When run on a DEC 2100 server with a large memory and eight parallel disks, the optimal algorithm for the PDM runs up to 144.7 times faster than in-core methods under demand paging. Moreover, even including I/O costs, the normalized times for the optimal PDM algorithm are competitive, or better than, those for in-core methods even when they run entirely in memory. } comment = { Similar paper to appear in Parallel Computing. Original version August 7, 1996; revised September 6, 1996 and August 14, 1997. (Compressed Postscript for September 1996 version.) } } @TechReport{Dartmouth:PCS-TR96-293, author = {Thomas H. Cormen and Melissa Hirschl }, title = {{Early Experiences in Evaluating the Parallel Disk Model with the ViC* Implementation}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-293}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/165/TR96-293.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/165/TR96-293.pdf}, abstract = { Although several algorithms have been developed for the Parallel Disk Model (PDM), few have been implemented. Consequently, little has been known about the accuracy of the PDM in measuring I/O time and total time to perform an out-of-core computation. This paper analyzes timing results on a uniprocessor with several disks for two PDM algorithms, out-of-core radix sort and BMMC permutations, to determine the strengths and weaknesses of the PDM. The results indicate the following. First, good PDM algorithms are usually not I/O bound. Second, of the four PDM parameters, two (problem size and memory size) are good indicators of I/O time and running time, but the other two (block size and number of disks) are not. Third, because PDM algorithms tend not to be I/O bound, asynchronous I/O effectively hides I/O times. The software interface to the PDM is part of the ViC* run-time library. The interface is a set of wrappers that are designed to be both efficient and portable across several parallel file systems and target machines. } comment = { Revised version appeared in Parallel Computing 23(4), June 1997. Original version August 7, 1996; revised version September 6, 1996. } } @TechReport{Dartmouth:PCS-TR96-292, author = {Dennis M. Healy and Daniel N. Rockmore and Sean S. B. Moore }, title = {{FFTs for the 2-Sphere-Improvements and Variations}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-292}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/164/TR96-292.pdf}, } @TechReport{Dartmouth:PCS-TR96-291, author = {Jonathan A. Moore }, title = {{Object Oriented Scenes for Virtual Light}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-291}, year = {1995}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/163/TR96-291.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/163/TR96-291.pdf}, abstract = { Ray tracing is one of many way to use a computer to generate an image. Ray tracers produce images by simulating light. Eliminating the details that might distract one from the interesting parts of ray tracing algorithms was purpose of my thesis project. The software I have written can be divide into three parts: the virtual frame buffer, the support classes and the ray tracing abstract base classes. The virtual frame buffer class, vfb, provides a simple means of rendering and studying the final image produced by a graphical algorithm. The support classes provide an elegant notation for the equations involved in ray tracing. The ray tracing base classes and associated classes provide a object oriented structure for defining the objects that make up a scene. } comment = { A Senior Undergraduate Honors Thesis in Computer Science.
Please see the TIFF images. } } @TechReport{Dartmouth:PCS-TR96-290, author = {Y. Joy Ko and Michael B. Taylor }, title = {{MRI On the Fly: Accelerating MRI Imaging Using LDA Classification with LDB Feature Extraction}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR96-290}, year = {1996}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/162/TR96-290.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/162/TR96-290.pdf}, abstract = { To improve MRI acquisition time, we explored the uses of linear discriminant analysis (LDA), and local discriminant bases (LDB) for the task of classifying MRI images using a minimal set of signal acquisitions. Our algorithm has both off-line and on-line components. The off-line component uses the k-basis algorithm to partition a set of training images (all from a particular region of a patient) into classes. For each class, we find a basis by applying the best basis algorithm on the images in that class. We keep these bases to be used by the on-line process. We then apply LDB to the training set with the class assignments, determining the best discriminant basis for the set. We rank the basis coordinates according to discriminating power, and retain the top M coordinates for the on-line algorithm. We keep the top M coordinates, which index the basis functions with the most discriminating capability, for on-line purposes. Finally, we train LDA on these transformed coordinates, producing a classifier for the images. With the off-line requirements complete, we can take advantage of the simplicity and speed of the on-line mechanism to acquire an image in a similar region of the patient. We need acquire only the M important coordinates of the image in the discriminant basis to create a ``scout image.'' This image, which can be acquired quickly since M is much much smaller than the number of measurements needed to fill in the values of the 256 by 256 pixels, is then sent through the map furnished by LDA which in turn assigns a class to the image. Returning to the list of bases that we kept from the k-bases algorithm, we find the optimal basis for the particular class at hand. We then acquire the image using that optimal basis, omitting the coefficients with the least truncation error. The complete image can then be quickly reconstructed using the inverse wavelet packet transform. The power of our algorithm is that the on-line task is fast and simple, while the computational complexity lies mostly in the off-line task that needs to be done only once for images in a certain region. In addition, our algorithm only makes use of the flexibility of MRI hardware, so no modifications in hardware design are needed. } comment = { A Senior Undergraduate Honors Thesis in Computer Science.
Postscript is 10 MB
uncompressed!
You can also retrieve this file in two pieces: A,
B
}
}
@TechReport{Dartmouth:PCS-TR96-289,
author = {Denis M. Serenyi },
title = {{Segmenting Workstation Screen Images}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-289},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/161/TR96-289.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/161/TR96-289.pdf},
abstract = {
None.
}
comment = {
A Senior Undergraduate Honors Thesis in Computer Science.
}
}
@TechReport{Dartmouth:PCS-TR96-288,
author = {Joel T. Thomas },
title = {{The Panda Array I/O Library on the Galley Parallel File System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-288},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/160/TR96-288.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/160/TR96-288.pdf},
abstract = {
The Panda Array I/O library, created at the University of Illinois, Urbana-Champaign,
was built especially to address the needs of high-performance scientific applications.
I/O has been one of the most frustrating bottlenecks to high performance for quite
some time, and the Panda project is an attempt to ameliorate this problem while
still providing the user with a simple, high-level interface. The Galley File System,
with its hierarchical structure of files and strided requests, is another attempt
at addressing the performance problem. My project was to redesign the Panda Array
library for use on the Galley file system. This project involved porting Panda's
three main functions: a checkpoint function for writing a large array periodically
for 'safekeeping,' a restart function that would allow a checkpointed file to be
read back in, and finally a timestep function that would allow the user to write
a group of large arrays several times in a sequence. Panda supports several different
distributions in both the compute-node memories and I/O-node disks.
We have found that the Galley File System provides a good environment on which to
build high-performance libraries, and that the mesh of Panda and Galley was a successful
combination.
}
comment = {
A Senior Undergraduate Honors Thesis.
}
}
@TechReport{Dartmouth:PCS-TR96-287,
author = {Scott M. Silver },
title = {{Implementation and Analysis of Software Based Fault Isolation}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-287},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/159/TR96-287.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/159/TR96-287.pdf},
abstract = {
Extensible applications rely upon user-supplied, untrusted modules to extend their
functionality. To remain reliable, applications must isolate themselves from user
modules. One method places each user module in a separate address space (process),
which uses hardware virtual memory support to isolate the user process. Costly inter-process
communication, however, prohibits frequent communication between the application
and the untrusted module. We implemented and analyzed a software method for isolating
an application from user modules. The technique uses a single address space. We
provide a logical address space and per-module access to system resources for each
module. Our software technique is a two-step process. First, we augment a module's
code so that it cannot access any address outside of an assigned range. Second,
we prevent the module from using system calls to access resources outside of its
fault domain.
This method for software isolation has two particular advantages over processes.
First, for frequently communicating modules, we significantly reduce context switch
time. Thus, we demonstrate near-optimal inter-module communication using software
fault isolation. Second, our software-based techniques provide an efficient and
expedient solution in situations where only one address space is available (e.g.,
kernel, or a single-address-space operating system).
}
comment = {
A Senior Undergraduate Honors Thesis in Computer Science.
}
}
@TechReport{Dartmouth:PCS-TR96-286,
author = {Nils Nieuwejaar and David Kotz },
title = {{The Galley Parallel File System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-286},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/158/TR96-286.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/158/TR96-286.pdf},
abstract = {
Most current multiprocessor file systems are designed to use multiple disks in parallel,
using the high aggregate bandwidth to meet the growing I/O requirements of parallel
scientific applications. Many multiprocessor file systems provide applications with
a conventional Unix-like interface, allowing the application to access multiple
disks transparently. This interface conceals the parallelism within the file system,
increasing the ease of programmability, but making it difficult or impossible for
sophisticated programmers and libraries to use knowledge about their I/O needs to
exploit that parallelism. In addition to providing an insufficient interface, most
current multiprocessor file systems are optimized for a different workload than
they are being asked to support. We introduce Galley, a new parallel file system
that is intended to efficiently support realistic scientific multiprocessor workloads.
We discuss Galley's file structure and application interface, as well as the performance
advantages offered by that interface.
}
comment = {
Revised version appeared in the journal Parallel
Computing. This paper is a combination of two papers, from ICS
'96 and a IOPADS '96.
}
}
@TechReport{Dartmouth:PCS-TR96-285,
author = {Robert S. Gray and David Kotz and Saurab Nog and Daniela Rus and George Cybenko },
title = {{Mobile agents for mobile computing}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-285},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/157/TR96-285.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/157/TR96-285.pdf},
abstract = {
Mobile agents are programs that can move through a network under their own control,
migrating from host to host and interacting with other agents and resources on each.
We argue that these mobile, autonomous agents have the potential to provide a convenient,
efficient and robust programming paradigm for distributed applications, particularly
when partially connected computers are involved. Partially connected computers include
mobile computers such as laptops and personal digital assistants as well as modem-connected
home computers, all of which are often disconnected from the network. In this paper,
we describe the design and implementation of our mobile-agent system, Agent Tcl,
and the specific features that support mobile computers and disconnected operation.
These features include network-sensing tools and a docking system that allows an
agent to transparently move between mobile computers, regardless of when the computers
connect to the network.
}
}
@TechReport{Dartmouth:PCS-TR96-283,
author = {Ting Cai and Peter A. Gloor and Saurab Nog },
title = {{DartFlow: A Workflow Management System on the Web using Transportable Agents}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-283},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/156/TR96-283.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/156/TR96-283.pdf},
abstract = {
Workflow management systems help streamline business processes and increase productivity.
This paper describes the design and implementation of the DartFlow workflow management
system. DartFlow uses Web-browser embedded Java applets as its front end and transportable
agents as the backbone. While Java applets provide a safe and platform independent
GUI, the use of transportable agents makes DartFlow highly flexible and scalable.
This paper describes the design and implementation of DartFlow, as well as a workflow
application that exploits DartFlow's agent-based design.
}
}
@TechReport{Dartmouth:PCS-TR96-282,
author = {Daniel N. Rockmore },
title = {{Some Applications of Generalized FFTs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-282},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/155/TR96-282.pdf},
abstract = {
Generalized FFTs are efficient algorithms for computing a Fourier transform of a
function defined on finite group, or a bandlimited function defined on a compact
group. The development of such algorithms has been accompanied and motivated by
a growing number of both potential and realized applications. This paper will attempt
to survey some of these applications. Appendices include some more detailed examples.
}
}
@TechReport{Dartmouth:PCS-TR96-281,
author = {David K. Maslen and Daniel N. Rockmore },
title = {{Generalized FFTS - A Survey of Some Recent Results}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-281},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/154/TR96-281.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/154/TR96-281.pdf},
abstract = {
In this paper we survey some recent work directed towards generalizing the fast Fourier
transform (FFT). We work primarily from the point of view of group representation
theory. In this setting the classical FFT can be viewed as a family of efficient
algorithms for computing the Fourier transform of either a function defined on a
finite abelian group, or a bandlimited function on a compact abelian group. We discuss
generalizations of the FFT to arbitrary finite groups and compact Lie groups.
}
comment = {
This will appear as part of the Proceedings for the 1994 Workshop in Groups and Computation,
DIMACS Series of the AMS, edited by Larry Finkelstein and William Kantor.
}
}
@TechReport{Dartmouth:PCS-TR96-280,
author = {Saurab Nog and Sumit Chawla and David Kotz },
title = {{An RPC Mechanism for Transportable Agents}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-280},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/153/TR96-280.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/153/TR96-280.pdf},
abstract = {
Transportable agents are autonomous programs that migrate from machine to machine,
performing complex processing at each step to satisfy client requests. As part of
their duties agents often need to communicate with other agents. We propose to use
remote procedure call (RPC) along with a flexible interface definition language
(IDL), to add structure to inter-agent communication. The real power of our Agent
RPC comes from a client-server binding mechanism based on flexible IDL matching
and from support for multiple simultaneous bindings. Our agents are programmed in
Agent Tcl; we describe how the Tcl implementation made RPC particularly easy to
implement. Finally, although our RPC is designed for Agent Tcl programs, the concepts
would also work for standard Tcl programs.
}
}
@TechReport{Dartmouth:PCS-TR96-279,
author = {Robert S. Gray },
title = {{Fast compression of transportable Tcl scripts}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-279},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/152/TR96-279.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/152/TR96-279.pdf},
abstract = {
An information agent is charged with the task of searching a collection of electronic
resources for information that is relevant to the user's current needs. These resources
are often distributed across a network and can contain tremendous quantities of
data. One of the paradigms that has been suggested for allowing efficient access
to such resources is transportable agents -- the agent is sent to the machine that
maintains the information resource; the agent executes on this remote machine and
then returns its results to the local machine. We have implemented a transportable
agent system that uses the Tool Command Language (Tcl) as the agent language.
Each Tcl script can suspend its execution at an arbitrary point, transport itself
to another machine and resume execution on the new machine. The execution state
of the script -- which includes the commands that have not been executed -- must
be transmitted to the new machine. Although the execution state tends to be small,
there will be a large number of agents moving across the network in a large-scale
system. Thus it is desirable to compress the execution state as much as possible.
Furthermore any compression scheme must be fast so that it does not become a bottleneck
between the transportable agent system and the network routines. In this paper we
explore several fast compression methods.
}
}
@TechReport{Dartmouth:PCS-TR96-278,
author = {Robert S. Gray and Daniela Rus and David Kotz },
title = {{Transportable Information Agents}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-278},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/151/TR96-278.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/151/TR96-278.pdf},
abstract = {
We have designed and implemented autonomous software agents. Autonomous software
agents navigate independently through a heterogeneous network. They are capable
of sensing the network configuration, monitoring software conditions, and interacting
with other agents. Autonomous agents are implemented as transportable programs,
e.g., programs that are capable of suspending execution, moving to a different machine,
and starting from where they left off. We illustrate the intelligent behavior of
autonomous agents in the context of distributed information-gathering tasks.
}
comment = {
Revised version to appear in AAAI '96 Workshop on Intelligent Adaptive Agents.
}
}
@TechReport{Dartmouth:PCS-TR96-277,
author = {Prasad Jayanti },
title = {{Compositional Reasoning is not possible in Determining the Solvability of Consensus}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-277},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/150/TR96-277.pdf},
abstract = {
Consensus, which requires processes with different input values to eventually agree
on one of these values, is a fundamental problem in fault-tolerant computing. We
study this problem in the context of asynchronous shared-memory systems. In our
model, shared-memory consists of a sequence of cells and supports a specific set
of operations. Prior research on consensus focussed on its solvability in shared-memories
supporting specific operations. In this paper, we investigate the following general
question: Let OP1 and OP2 be any two sets of operations such that each set includes
read and write operations. Suppose there is no consensus protocol for N processes
in a shared-memory that supports only operations in OP1 and in a shared-memory that
supports only operations in OP2. Does it follow that there is no consensus protocol
for N processes in a shared-memory that supports all operations in OP1 and all operations
in OP_2? This question is in the same spirit as the robustness question, but there
are significant differences, both conceptually and in the models of shared-memory
for which the two questions are studied. For deterministic types, the robustness
question has been known to have a positive answer, In contrast, we prove that the
answer to the question posed above is negative even if operations are deterministic.
}
}
@TechReport{Dartmouth:PCS-TR96-271,
author = {Sumit Chawla and Dennis M. Healy },
title = {{A Fast Parallel Implementation of the Wavelet Packet Best Basis Algorithm on the MP-2 for Real-Time MRI}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-271},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/149/TR96-271.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/149/TR96-271.pdf, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/149/TR96-271.pdf},
abstract = {
Adaptive signal representations such as those determined by best-basis type algorithms
have found extensive application in image processing, although their use in real-time
applications may be limited by the complexity of the algorithm. In contrast to the
wavelet transform which can be computed in O(n) time, the full wavelet packet expansion
required for the standard best basis search takes O(n log n) time to compute. In
the parallel world, however, both transforms take O(log n) to compute when the number
of processors equal the number of data elements, making the wavelet packet expansion
attractive to implement. This note describes near real-time performance obtained
with a parallel implementation of best basis algorithms for Wavelet Packet bases.
The platform for our implementation is a DECmpp 12000/Sx 2000, a parallel machine
identical to the MasPar MP-2. The DECmpp is a single instruction, multiple data
(SIMD) system; such systems support a data parallel programming model, a model well
suited to the task at hand. We have implemented the 1D and the 2D WPT on this machine
and our results show a significant speedup over the sequential counterparts. In
the 1D case we almost attain the theoretical speedup, while in the 2D case we increase
execution speed by about two orders of magnitude. The current implementation of
the 1D transform is limited to signals of length 2048, and the 2D transform is limited
to images of size: 32x32, 64x64, and 128x128. We are currently working on extending
our transform to handle signals and images of larger size.
}
}
@TechReport{Dartmouth:PCS-TR96-257,
author = {Saurab Nog and Carl J. Beckmann },
title = {{A Queuing Analysis of Bandwidth Allocation Schemes for Compressed Video}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-257},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/148/TR96-257.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/148/TR96-257.pdf},
abstract = {
Video and audio compression techniques allow continuous media streams to be transmitted
at bit rates that are a function of the delivered quality of service. Digital networks
will be increasingly used for the transmission of such continuous media streams.
This paper describes an admission control policy in which the quality of service
is negotiated at stream initiation, and is a function of both the desired quality
of service and the available bandwidth resources. The advantage of this approach
is the ability to robustly service large numbers of users, while providing increased
quality of service during low usage periods. Several simple algorithms for implementing
this policy are described and evaluated using queuing model analysis applied to
video-on-demand. The queuing model results are compared with simulation results
to validate their accuracy.
}
comment = {
Revised on 3/25/96 to include discrete event simulation results.
}
}
@TechReport{Dartmouth:PCS-TR96-255,
author = {Daniela Rus and Devika Subramanian },
title = {{Information retrieval, information structure, and information agents}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR96-255},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/147/TR96-255.pdf},
abstract = {
This paper presents a customizable architecture for software agents that capture
and access information in large, heterogeneous, distributed electronic repositories.
The key idea is to exploit underlying structure at various levels of granularity
to build high-level indices with task-specific interpretations. Information agents
construct such indices and are configured as a network of reusable modules called
structure detectors and segmenters. We illustrate our architecture with the design
and implementation of smart information filters in two contexts: retrieving stock
market data from Internet newsgroups, and retrieving technical reports from Internet
ftp sites.
}
}
@TechReport{Dartmouth:PCS-TR95-273,
author = {Saurab Nog and David Kotz },
title = {{A Performance Comparison of TCP/IP and MPI on FDDI, Fast Ethernet, and Ethernet}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-273},
year = {1996},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/146/TR95-273.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/146/TR95-273.pdf},
abstract = {
Communication is a very important factor affecting distributed applications. Getting
a close handle on network performance (both bandwidth and latency) is thus crucial
to understanding overall application performance. We benchmarked some of the metrics
of network performance using two sets of experiments, namely roundtrip and datahose.
The tests were designed to measure a combination of network latency, bandwidth,
and contention. We repeated the tests for two protocols (TCP/IP and MPI) and three
networks (100 Mbit FDDI (Fiber Distributed Data Interface), 100 Mbit Fast Ethernet,
and 10 Mbit Ethernet). The performance results provided interesting insights into
the behaviour of these networks under different load conditions and the software
overheads associated with an MPI implementation (MPICH). This document presents
details about the experiments, their results, and our analysis of the performance.
Revised on 1/8/96 to emphasize our use of a particular MPI implementation, MPICH.
}
}
@TechReport{Dartmouth:PCS-TR95-272,
author = {Stavros G. Kolliopoulos and Clifford Stein },
title = {{Finding Real-Valued Single-Source Shortest Paths in o(n^3) Expected Time}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-272},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/145/TR95-272.pdf},
abstract = {
Given an $n$-vertex directed network $G$ with real costs on the edges and a designated
source vertex $s$, we give a new algorithm to compute shortest paths from $s$. Our
algorithm is a simple deterministic one with $O(n^2 log n)$ expected running time
over a large class of input distributions.
The shortest path problem is an old and fundamental problem with a host of applications.
Our algorithm is the first strongly-polynomial algorithm in over 35 years to improve
upon some aspect of the running time of the celebrated Bellman-Ford algorithm for
arbitrary networks, with any type of cost assignments.
}
}
@TechReport{Dartmouth:PCS-TR95-271,
author = {Sumit Chawla and Dennis M. Healy },
title = {{A Fast Parallel Implementation of the Wavelet Packet Best Basis Algorithm on the MP-2 for Real-Time MRI}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-271},
year = {1996},
month = {January},
abstract = {
This technical report is equivalent to technical report PCS-TR96-271, issued in October
1996.
}
comment = {
See report PCS-TR96-271.
}
}
@TechReport{Dartmouth:PCS-TR95-270,
author = {David Kotz },
title = {{Interfaces for Disk-Directed I/O}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-270},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/143/TR95-270.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/143/TR95-270.pdf},
abstract = {
In other papers I propose the idea of disk-directed I/O for multiprocessor file systems.
Those papers focus on the performance advantages and capabilities of disk-directed
I/O, but say little about the application-programmer's interface or about the interface
between the compute processors and I/O processors. In this short note I discuss
the requirements for these interfaces, and look at many existing interfaces for
parallel file systems. I conclude that many of the existing interfaces could be
adapted for use in a disk-directed I/O system.
}
}
@TechReport{Dartmouth:PCS-TR95-267,
author = {Elizabeth A. M. Shriver and Leonard F. Wisniewski },
title = {{An API for Choreographing Data Accesses}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-267},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/142/TR95-267.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/142/TR95-267.pdf},
abstract = {
Current APIs for multiprocessor multi-disk file systems are not easy to use in developing
out-of-core algorithms that choreograph parallel data accesses. Consequently, the
efficiency of these algorithms is hard to achieve in practice. We address this deficiency
by specifying an API that includes data-access primitives for data choreography.
With our API, the programmer can easily access specific blocks from each disk in
a single operation, thereby fully utilizing the parallelism of the underlying storage
system. Our API supports the development of libraries of commonly-used higher-level
routines such as matrix-matrix addition, matrix-matrix multiplication, and BMMC
(bit-matrix-multiply/complement) permutations. We illustrate our API in implementations
of these three high-level routines to demonstrate how easy it is to use.
}
comment = {
Also published as Courant Institute Tech Report 708.
}
}
@TechReport{Dartmouth:PCS-TR95-266,
author = {Sean S. B. Moore and Leonard F. Wisniewski },
title = {{Complexity Analysis of Two Permutations Used by Fast Cosine Transform Algorithms}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-266},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/141/TR95-266.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/141/TR95-266.pdf},
abstract = {
Recently developed fast cosine transform (FCT) algorithms require fewer operations
than any other known general algorithm. Similar to related fast transform algorithms
(e.g., the FFT), these algorithms permute the data before, during, or after the
computation of the transform. The choice of this permutation may be an important
consideration in reducing the complexity of the permutation algorithm. In this paper,
we derive the complexity to generate the permutation mappings used in these FCT
algorithms for power-of-2 data sets by representing them as linear index transformations
and translating them into combinational circuits. Moreover, we show that one of
these permutations not only allows efficient implementation, but is also self-invertible,
i.e., we can use the same circuit to generate the permutation mapping for both the
fast cosine transform and its inverse, like the bit-reversal permutation used by
FFT algorithms. These results may be useful to designers of low-level algorithms
for implementing fast cosine transforms.
}
}
@TechReport{Dartmouth:PCS-TR95-265,
author = {Leonard F. Wisniewski },
title = {{Structured Permuting in Place on Parallel Disk Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-265},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/140/TR95-265.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/140/TR95-265.pdf},
abstract = {
The ability to perform permutations of large data sets in place reduces the amount
of necessary available disk storage. The simplest way to perform a permutation often
is to read the records of a data set from a source portion of data storage, permute
them in memory, and write them to a separate target portion of the same size. It
can be quite expensive, however, to provide disk storage that is twice the size
of very large data sets. Permuting in place reduces the expense by using only a
small amount of extra disk storage beyond the size of the data set. This paper features
in-place algorithms for commonly used structured permutations. We have developed
an asymptotically optimal algorithm for performing BMMC (bit-matrix-multiply/complement)
permutations in place that requires at most $frac{2N}{BD}left( 2ceil{frac{rank{gamma}}{lg
(M/B)}} + frac{7}{2}right)$ parallel disk accesses, as long as $M geq 2BD$, where
$N$ is the number of records in the data set, $M$ is the number of records that
can fit in memory, $D$ is the number of disks, $B$ is the number of records in a
block, and $gamma$ is the lower left $lg (N/B) times lg B$ submatrix of the characteristic
matrix for the permutation. This algorithm uses $N+M$ records of disk storage and
requires only a constant factor more parallel disk accesses and insignificant additional
computation than a previously published asymptotically optimal algorithm that uses
$2N$ records of disk storage. We also give algorithms to perform mesh and torus
permutations on a $d$-dimensional mesh. The in-place algorithm for mesh permutations
requires at most $3ceil{N/BD}$ parallel I/Os and the in-place algorithm for torus
permutations uses at most $4dN/BD$ parallel I/Os. The algorithms for mesh and torus
permutations require no extra disk space as long as the memory size~$M$ is at least~$3BD$.
The torus algorithm improves upon the previous best algorithm in terms of both time
and space.
}
}
@TechReport{Dartmouth:PCS-TR95-264,
author = {Matt Bishop and Mark Valence and Leonard F. Wisniewski },
title = {{Process Migration for Heterogeneous Distributed Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-264},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/139/TR95-264.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/139/TR95-264.pdf},
abstract = {
The policies and mechanisms for migrating processes in a distributed system become
more complicated in a heterogeneous environment, where the hosts may differ in their
architecture and operating systems. These distributed systems include a large quantity
and great diversity of resources which may not be fully utilized without the means
to migrate processes to the idle resources. In this paper, we present a graph model
for single process migration which can be used for load balancing as well as other
non-traditional scenarios such as migration during the graceful degradation of a
host. The graph model provides the basis for a layered approach to implementing
the mechanisms for process migration in a Heterogeneous Migration Facility (HMF).
HMF provides the user with a library to automatically migrate processes and checkpoint
data.
}
}
@TechReport{Dartmouth:PCS-TR95-263,
author = {Nils Nieuwejaar and David Kotz and Apratim Purakayastha and Carla Schlatter Ellis and Michael Best },
title = {{File-Access Characteristics of Parallel Scientific Workloads}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-263},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/138/TR95-263.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/138/TR95-263.pdf},
abstract = {
Phenomenal improvements in the computational performance of multiprocessors have
not been matched by comparable gains in I/O system performance. This imbalance has
resulted in I/O becoming a significant bottleneck for many scientific applications.
One key to overcoming this bottleneck is improving the performance of parallel file
systems.
The design of a high-performance parallel file system requires a comprehensive understanding
of the expected workload. Unfortunately, until recently, no general workload studies
of parallel file systems have been conducted. The goal of the CHARISMA project was
to remedy this problem by characterizing the behavior of several production workloads,
on different machines, at the level of individual reads and writes. The first set
of results from the CHARISMA project describe the workloads observed on an Intel
iPSC/860 and a Thinking Machines CM-5. This paper is intended to compare and contrast
these two workloads for an understanding of their essential similarities and differences,
isolating common trends and platform-dependent variances. Using this comparison,
we are able to gain more insight into the general principles that should guide parallel
file-system design.
}
comment = {
See also the related papers from Supercomputing
'94, IEEE Parallel and Distributed Technology,
and IPPS '95
}
}
@TechReport{Dartmouth:PCS-TR95-262,
author = {Chris Armen and Clifford Stein },
title = {{A 2-2/3 Approximation for the Shortest Superstring Problem}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-262},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/137/TR95-262.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/137/TR95-262.pdf},
abstract = {
Given a collection of strings S={s_1, ..., s_n} over an alphabet Sigma, a superstring
alpha of S is a string containing each s_i as a substring; that is, for each i,
1<=i<=n, alpha contains a block of |s_i| consecutive characters that match s_i exactly.
The shortest superstring problem is the problem of finding a superstring alpha of
minimum length.
The shortest superstring problem has applications in both data compression and
computational biology. In data compression, the problem is a part of a general model
of string compression proposed by Gallant, Maier and Storer (JCSS '80). Much of
the recent interest in the problem is due to its application to DNA sequence assembly.
The problem has been shown to be NP-hard; in fact, it was shown by Blum et al.(JACM
'94) to be MAX SNP-hard. The first O(1)-approximation was also due to Blum et al.,
who gave an algorithm that always returns a superstring no more than 3 times the
length of an optimal solution. Several researchers have published results that improve
on the approximation ratio; of these, the best previous result is our algorithm
ShortString, which achieves a 2 3/4-approximation (WADS '95).
We present our new algorithm, G-ShortString, which achieves a ratio of 2 2/3. It
generalizes the ShortString algorithm, but the analysis differs substantially from
that of ShortString. Our previous work identified classes of strings that have a
nested periodic structure, and which must be present in the worst case for our algorithms.
We introduced machinery to descibe these strings and proved strong structural properties
about them. In this paper we extend this study to strings that exhibit a more relaxed
form of the same structure, and we use this understanding to obtain our improved
result.
}
}
@TechReport{Dartmouth:PCS-TR95-261,
author = {Robert S. Gray },
title = {{Ph.D. Thesis Proprosal: Transportable Agents}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-261},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/136/TR95-261.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/136/TR95-261.pdf},
abstract = {
One of the paradigms that has been suggested for allowing efficient access to remote
resources is transportable agents. A transportable agent is a named program that
can migrate from machine to machine in a heterogeneous network. The program chooses
when and where to migrate. It can suspend its execution at an arbitrary point, transport
to another machine and resume execution on the new machine. Transportable agents
have several advantages over the traditional client/server model. Transportable
agents consume less network bandwidth and do not require a connection between communicating
machines -- this is attractive in all networks and particularly attractive in wireless
networks. Transportable agents are a convenient paradigm for distributed computing
since they hide the communication channels but not the location of the computation.
Transportable agents allow clients and servers to program each other. However transportable
agents pose numerous challenges such as security, privacy and efficiency. Existing
transportable agent systems do not meet all of these challenges. In addition there
has been no formal characterization of the performance of transportable agents.
This thesis addresses these weakness. The thesis has two parts -- (1) formally characterize
the performance of transportable agents through mathematical analysis and network
simulation and (2) implement a complete transportable agent system.
}
}
@TechReport{Dartmouth:PCS-TR95-260,
author = {Song Bac Toh },
title = {{Simulation of a Video-on-Demand System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-260},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/135/TR95-260.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/135/TR95-260.pdf},
abstract = {
This paper presents a simulation study of a video-on-demand system. The focus of
the study is the effectiveness of different caching strategies on a video-on-demand
system with two levels of cache, RAM and disks, in front of a tape library. Using
an event-driven simulator, I show that caching was helpful in increasing the service
capacity of the system. On-demand caching showed its advantages especially when
the requests were clustered around a few popular titles (in other words, there was
temporal locality).
}
comment = {
A Senior Honors Thesis in Computer Science.
}
}
@TechReport{Dartmouth:PCS-TR95-259,
author = {Scott R. Cushman },
title = {{A Multiple Discrete Pass Algorithm on a DEC Alpha 2100}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-259},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/134/TR95-259.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/134/TR95-259.pdf},
comment = {
Senior Honors Thesis. No abstract. This thesis presents the results of an I/O-intensive
algorithm on a DEC Alpha 2100 with an eight-disk array.
}
}
@TechReport{Dartmouth:PCS-TR95-258,
author = {Kenneth Harker },
title = {{TIAS: A Transportable Intelligent Agent System}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-258},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/133/TR95-258.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/133/TR95-258.pdf},
abstract = {
In recent years, there has been an explosive growth in the amount of information
available to our society. In particular, the amount of information available on-line
through vast networks like the global Internet has been growing at a staggering
rate. This growth rate has by far exceeded the rate of growth in network speeds,
as has the number of individuals and organizations seeking access to this information.
There is thus a motivation to find abstract methods of manipulating this on-line
data in ways that both serve the needs of end users efficiently and use network
resources intelligently. In lieu of a traditional client-server model of information
processing, which is both inflexible and potentially very inefficient, a Transportable
Intelligent Agent system has the potential to achieve a more efficient and flexible
network system. An intelligent agent is a program that models the information space
for a user, and allows the user to specify how the information is to be processed.
A transportable agent can suspend its execution, transport itself to a new location
on a network, and resume execution at the new location. This is a particularly attractive
model for both wireless and dialup networks where a user might not be able to maintain
a permanent network connection, as well as for situations where the amount of information
to be processed is large relative to the network bandwidth. Preliminary work in
the field has shown that such agent systems are possible and deserve further study.
This thesis describes a prototype transportable intelligent agent system that extends
work already done in the field. Agents are written in a modified version of the
Tcl programming language and transported using TCP/IP connections. Several simple
examples demonstrate the properties of the system.
}
comment = {
A Senior Honors Thesis in Computer Science.
}
}
@TechReport{Dartmouth:PCS-TR95-256,
author = {Fillia Makedon and Samuel A. Rebelsky and Matthew Cheyney and Charles B. Owen and Peter A. Gloor },
title = {{Issues and Obstacles with Multimedia Authoring (renumbered)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-256},
year = {1995},
month = {January},
comment = {
This Technical Report report has occasionally been cited (incorrectly) as TR95-256.
TR94-207 is the correct number. On the web, see TR94-207.
}
}
@TechReport{Dartmouth:PCS-TR95-254,
author = {David Kotz },
title = {{Expanding the Potential for Disk-Directed I/O}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-254},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/131/TR95-254.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/131/TR95-254.pdf},
abstract = {
As parallel computers are increasingly used to run scientific applications with large
data sets, and as processor speeds continue to increase, it becomes more important
to provide fast, effective parallel file systems for data storage and for temporary
files. In an earlier work we demonstrated that a technique we call disk-directed
I/O has the potential to provide consistent high performance for large, collective,
structured I/O requests. In this paper we expand on this potential by demonstrating
the ability of a disk-directed I/O system to read irregular subsets of data from
a file, and to filter and distribute incoming data according to data-dependent functions.
}
comment = {
Revised version appeared in SPDP'95.
}
}
@TechReport{Dartmouth:PCS-TR95-253,
author = {Nils Nieuwejaar and David Kotz },
title = {{Low-level Interfaces for High-level Parallel I/O}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-253},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/130/TR95-253.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/130/TR95-253.pdf},
abstract = {
As the I/O needs of parallel scientific applications increase, file systems for multiprocessors
are being designed to provide applications with parallel access to multiple disks.
Many parallel file systems present applications with a conventional Unix-like interface
that allows the application to access multiple disks transparently. By tracing all
the activity of a parallel file system in a production, scientific computing environment,
we show that many applications exhibit highly regular, but non-consecutive I/O access
patterns. Since the conventional interface does not provide an efficient method
of describing these patterns, we present three extensions to the interface that
support strided, nested-strided, and nested-batched I/O requests. We show how these
extensions can be used to express common access patterns.
}
comment = {
This TR supercedes PCS-TR94-230. A result of the CHARISMA
project. Appeared in IOPADS '95 at IPPS '95.
}
}
@TechReport{Dartmouth:PCS-TR95-252,
author = {Robert S. Gray },
title = {{Content-based image retrieval: color and edges}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-252},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/129/TR95-252.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/129/TR95-252.pdf},
abstract = {
One of the tools that will be essential for future electronic publishing is a powerful
image retrieval system. The author should be able to search an image database for
images that convey the desired information or mood; a reader should be able to search
a corpus of published work for images that are relevant to his or her needs. Most
commercial image retrieval systems associate keywords or text with each image and
require the user to enter a keyword or textual description of the desired image.
This text-based approach has numerous drawbacks -- associating keywords or text
with each image is a tedious task; some image features may not be mentioned in the
textual description; some features are ``nearly impossible to describe with text'';
and some features can be described in widely different ways [Niblack, 1993].
In an effort to overcome these problems and improve retrieval performance, researchers
have focused more and more on content-based image retrieval in which retrieval is
accomplished by comparing image features directly rather than textual descriptions
of the image features. Features that are commonly used in content-based retrieval
include color, shape, texture and edges. In this report we describe a simple content-based
system that retrieves color images on the basis of their color distributions and
edge characteristics. The system uses two retrieval techniques that have been described
in the literature -- i.e. histogram intersection to compare color distributions
and sketch comparison to compare edge characteristics.
The performance of the system is evaluated and various extensions to the existing
techniques are proposed.
}
}
@TechReport{Dartmouth:PCS-TR95-251,
author = {David Kotz },
title = {{Disk-directed I/O for an Out-of-Core Computation}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-251},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/128/TR95-251.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/128/TR95-251.pdf},
abstract = {
New file systems are critical to obtain good I/O performance on large multiprocessors.
Several researchers have suggested the use of collective file-system operations,
in which all processes in an application cooperate in each I/O request. Others have
suggested that the traditional low-level interface (read, write, seek) be augmented
with various higher-level requests (e.g., read matrix), allowing the programmer
to express a complex transfer in a single (perhaps collective) request. Collective,
high-level requests permit techniques like two-phase I/O and disk-directed I/O to
significantly improve performance over traditional file systems and interfaces.
Neither of these techniques have been tested on anything other than simple benchmarks
that read or write matrices. Many applications, however, intersperse computation
and I/O to work with data sets that cannot fit in main memory. In this paper, we
present the results of experiments with an ``out-of-core'' LU-decomposition program,
comparing a traditional interface and file system with a system that has a high-level,
collective interface and disk-directed I/O. We found that a collective interface
was awkward in some places, and forced additional synchronization. Nonetheless,
disk-directed I/O was able to obtain much better performance than the traditional
system.
}
comment = {
A revised version of this report appeared in HPDC
'95.
}
}
@TechReport{Dartmouth:PCS-TR95-250,
author = {Thomas H. Cormen and Sumit Chawla and Preston Crow and Melissa Hirschl and Roberto Hoyle and Keith D. Kotay and Rolf H. Nelson and Nils Nieuwejaar and Scott M. Silver and Michael B. Taylor },
title = {{DartCVL: The Dartmouth C Vector Library}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR95-250},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/127/TR95-250.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/127/TR95-250.pdf},
abstract = {
As a class project, we implemented a version of CVL, the C Vector Library, on a DECmpp
12000/Sx 2000, which is equivalent to the MasPar MP-2 massively parallel computer.
We compare our implementation, DartCVL, to the University of North Carolina implementation,
UnCvl.
DartCVL was designed for the MP-2 architecture and UnCvl was designed for the MP-1.
Because the MasPar MP-1 and MP-2 are functionally equivalent, both DartCVL and UnCvl
will run on either. Differences in the designs of the two machines, however, may
lead to different software design decisions. DartCVL differs from UnCvl in two key
ways. First, DartCVL uses hierarchical virtualization, whereas UnCvl uses cut-and-stack.
Second, DartCVL runs as much serial code as possible on the console, whereas UnCvl
runs all serial code on the Array Control Unit (ACU). The console (a DECstation
5000/240 at Dartmouth) has a significantly faster serial processor than the ACU.
DartCVL is optimized for the MP-2, and our timing results indicate that it usually
runs faster than UnCvl on the 2048-processor machine at Dartmouth.
}
}
@TechReport{Dartmouth:PCS-TR94-243,
author = {Thomas H. Cormen and Alex Colvin },
title = {{ViC*: A Preprocessor for Virtual-Memory C*}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-243},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/126/TR94-243.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/126/TR94-243.pdf},
abstract = {
This paper describes the functionality of ViC*, a compiler-like preprocessor for
out-of-core C*. The input to ViC* is a C* program but with certain shapes declared
verb`outofcore`, which means that all parallel variables of these shapes reside
on disk. The output is a standard C* program with the appropriate I/O and library
calls added for efficient access to out-of-core parallel variables.
}
}
@TechReport{Dartmouth:PCS-TR94-241,
author = {Samuel A. Rebelsky and Fillia Makedon and James Matthews and Charles B. Owen and Laura Bright and Kenneth Harker and Nancy Toth and Panagiotis Metaxas },
title = {{Building Multimedia Proceedings: The Roles of Video in Interactive Electronic Conference Proceedings}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-241},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/125/TR94-241.pdf},
}
@TechReport{Dartmouth:PCS-TR94-240,
author = {Samuel A. Rebelsky },
title = {{Incremental Equational Programming}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-240},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/124/TR94-240.pdf},
}
@TechReport{Dartmouth:PCS-TR94-239,
author = {Samuel A. Rebelsky and James Ford and Kenneth Harker and Fillia Makedon and Panagiotis Metaxas and Charles B. Owen },
title = {{The Design and Development of Interactive Multimedia Conference Proceedings}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-239},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/123/TR94-239.pdf},
}
@TechReport{Dartmouth:PCS-TR94-238,
author = {Peter Su },
title = {{Efficient Parallel Algorithms for Closest Point Problems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-238},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/122/TR94-238.pdf},
abstract = {
This dissertation develops and studies fast algorithms for solving closest point
problems. Algorithms for such problems have applications in many areas including
statistical classification, crystallography, data compression, and finite element
analysis. In addition to a comprehensive empirical study of known sequential methods,
I introduce new parallel algorithms for these problems that are both efficient and
practical. I present a simple and flexible programming model for designing and analyzing
parallel algorithms. Also, I describe fast parallel algorithms for nearest-neighbor
searching and constructing Voronoi diagrams. Finally, I demonstrate that my algorithms
actually obtain good performance on a wide variety of machine architectures.
The key algorithmic ideas that I examine are exploiting spatial locality, and random
sampling. Spatial decomposition provides allows many concurrent threads to work
independently of one another in local areas of a shared data structure. Random sampling
provides a simple way to adaptively decompose irregular problems, and to balance
workload among many threads. Used together, these techniques result in effective
algorithms for a wide range of geometric problems.
The key experimental ideas used in my thesis are simulation and animation. I use
algorithm animation to validate algorithms and gain intuition about their behavior.
I model the expected performance of algorithms using simulation experiences, and
some knowledge as to how much critical primitive operations will cost on a given
machine. In addition, I do this without the burden of esoteric computational models
that attempt to cover every possible variable in the design of a computer system.
An iterative process of design, validation, and simulation delays the actual implementation
until as many details as possible are accounted for. Then, further experiments are
used to turn the implementations for better performance.
}
comment = {
Advisor: Scot Drysdale
}
}
@TechReport{Dartmouth:PCS-TR94-236,
author = {Perry Fizzano and Clifford Stein },
title = {{Distributed Scheduling in Finite Capacity Networks}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-236},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/121/TR94-236.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/121/TR94-236.pdf},
abstract = {
We consider the problem of scheduling unit-sized jobs in a distributed network of
processors. Each processor only knows the number of jobs it and its neighbors have.
We give an analysis of intuitive algorithm and prove that the algorithm produces
schedules that are within a logarithmic factor of the length of the optimal schedule
given that the optimal schedule is sufficiently long.
}
}
@TechReport{Dartmouth:PCS-TR94-235,
author = {David Kotz },
title = {{A DAta-Parallel Programming Library for Education (DAPPLE)}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-235},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/120/TR94-235.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/120/TR94-235.pdf},
abstract = {
In the context of our overall goal to bring the concepts of parallel computing into
the undergraduate curriculum, we set out to find a parallel-programming language
for student use. To make it accessible to students at all levels, and to be independent
of any particular hardware platform, we chose to design our own language, based
on a data-parallel model and on C++. The result, DAPPLE, is a C++ class library
designed to provide the illusion of a data-parallel programming language on conventional
hardware and with conventional compilers. DAPPLE defines Vectors and Matrices as
basic classes, with all the usual C++ operators overloaded to provide elementwise
arithmetic. In addition, DAPPLE provides typical data-parallel operations like scans,
permutations, and reductions. Finally, DAPPLE provides a parallel if-then-else statement
to restrict the scope of the above operations to partial vectors or matrices.
}
comment = {
A revision of this report appeared in SIGCSE
'95.
}
}
@TechReport{Dartmouth:PCS-TR94-233,
author = {Tom Leighton and Fillia Makedon and Spyros Tragoudas },
title = {{Hypergraph Partitioning Algorithms}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-233},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/119/TR94-233.pdf},
abstract = {
We present the first polynomial time approximation algorithms for the balanced hypergraph
partitioning problem. The approximations are within polylogarithmic factors of the
optimal solutions. The choice of algorithm involves a time complexity/approximation
bound tradeoff. We employ a two step methodology. First we approximate the flux
of the input hypergraph. This involves an approximate solution to a concurrent flow
problem on the hypergraph. In the second step we use the approximate flux to obtain
approximations for the balanced bipartitioning problem. Our results extend the approximation
algorithms by Leighton-Rao on graphs to hypergraphs. We also give the first polylogarithmic
times optimal approximation algorithms for multiway (graph and hypergraph) partitioning
problems into bounded size sets.
A better approximation algorithm for the latter problem is finally presented for
the special case of bounded sets of size at most O(log n) on planar graphs and hypergraphs,
where n is the number of nodes of the input instance.
}
}
@TechReport{Dartmouth:PCS-TR94-232,
author = {David Kotz and Ting Cai },
title = {{Exploring the Use of I/O Nodes for Computation in a MIMD Multiprocessor}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-232},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/118/TR94-232.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/118/TR94-232.pdf},
abstract = {
As parallel systems move into the production scientific computing world, the emphasis
will be on cost-effective solutions that provide high throughput for a mix of applications.
Cost-effective solutions demand that a system make effective use of all of its resources.
Many MIMD multiprocessors today, however, distinguish between ``compute'' and ``I/O''
nodes, the latter having attached disks and being dedicated to running the file-system
server. This static division of responsibilities simplifies system management but
does not necessarily lead to the best performance in workloads that need a different
balance of computation and I/O.
Of course, computational processes sharing a node with a file-system service may
receive less CPU time, network bandwidth, and memory bandwidth than they would on
a computation-only node. In this paper we examine this issue experimentally. We
found that high-performance I/O does not necessarily require substantial CPU time,
leaving plenty of time for application computation. There were some complex file-system
requests, however, which left little CPU time available to the application. (The
impact on network and memory bandwidth still needs to be determined.) For applications
(or users) that cannot tolerate an occasional interruption, we recommend that they
continue to use only compute nodes. For tolerant applications needing more cycles
than those provided by the compute nodes, we recommend that they take full advantage
of both compute and I/O nodes for computation, and that operating systems should
make this possible.
}
comment = {
Revised version appeared in IOPADS '95 at IPPS '95,
pages 78-89.
}
}
@TechReport{Dartmouth:PCS-TR94-231,
author = {Fillia Makedon and James Matthews and Charles B. Owen and Samuel A. Rebelsky },
title = {{Multimedia authoring, development environments, and digital video editing.}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-231},
year = {0001},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/117/TR94-231.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/117/TR94-231.pdf},
abstract = {
Multimedia systems integrate text, audio, video, graphics, and other media and allow
them to be utilized in a combined and interactive manner. Using this exciting and
rapidly developing technology, multimedia applications can provide extensive benefits
in a variety of arenas, including research, education, medicine, and commerce. While
there are many commercial multimedia development packages, the easy and fast creation
of a useful, full-featured multimedia document is not yet a straightforward task.
This paper addresses issues in the development of multimedia documents, ranging
from user-interface tools that manipulate multimedia documents to multimedia communication
technologies such as compression, digital video editing and information retrieval.
It outlines the basic steps in the multimedia authoring process and some of the
requirements that need to be met by multimedia development environments. It also
presents the role of video, an essential component of multimedia systems and the
role of programming in digital video editing. A model is described for remote access
of distributed video. The paper concludes with a discussion of future research directions
and new uses of multimedia documents.
}
comment = {
Appeared in: Proc. of SPIE Defining the Global Information Infrastructure: Systems
and Services (Critical Review), Boston, MA, 11/2/94.
}
}
@TechReport{Dartmouth:PCS-TR94-230,
author = {Nils Nieuwejaar and David Kotz },
title = {{A Multiprocessor Extension to the Conventional File System Interface}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-230},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/116/TR94-230.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/116/TR94-230.pdf},
abstract = {
As the I/O needs of parallel scientific applications increase, file systems for multiprocessors
are being designed to provide applications with parallel access to multiple disks.
Many parallel file systems present applications with a conventional Unix-like interface
that allows the application to access multiple disks transparently. By tracing all
the activity of a parallel file system in a production, scientific computing environment,
we show that many applications exhibit highly regular, but non-consecutive I/O access
patterns. Since the conventional interface does not provide an efficient method
of describing these patterns, we present an extension which supports strided and
nested-strided I/O requests.
}
comment = {
A result of the CHARISMA project. This report has
been superceded by report PCS-TR95-253.
}
}
@TechReport{Dartmouth:PCS-TR94-229,
author = {David R. Karger and Clifford Stein },
title = {{A New Approach to the Minumum Cut Problem}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-229},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/115/TR94-229.pdf},
}
@TechReport{Dartmouth:PCS-TR94-227,
author = {Robert Beals and Daniel N. Rockmore and Ki-Seng Tan },
title = {{Deciding Finiteness for Matrix Groups Over Function Fields}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-227},
year = {1995},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/114/TR94-227.pdf},
abstract = {
Let S be any finite subset GLn(F(t)) where F is a field. In this paper we give algorithms
to decide if the group generated by S is finite. In the case of characteristic zero,
slight modifications of earlier work of Babai, Beals and Rockmore [1] give polynomial
time deterministic algorithms to solve this problem. The case of positive characteristic
turns out to be more subtle and our algorithms depend on a structure theorem proved
here, generalizing a theorem of Weil. We also present a fairly detailed analysis
of the size of finite subgroups in this case and give bounds which depend upon the
number of generators. To this end we also introduce the notion of the diameter of
a finitely generated algebra and derive some upper bounds related to this quantity.
In positive characteristic the deterministic algorithms we present are exponential.
A randomized algorithm based on ideas of the Meat-Axe is also given. While not provably
efficient, the success of the Meat-Axe suggests the randomized algorithm will be
useful.
}
}
@TechReport{Dartmouth:PCS-TR94-226,
author = {David Kotz },
title = {{Disk-directed I/O for MIMD Multiprocessors}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-226},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/113/TR94-226.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/113/TR94-226.pdf},
abstract = {
Many scientific applications that run on today's multiprocessors are bottlenecked
by their file I/O needs. Even if the multiprocessor is configured with sufficient
I/O hardware, the file-system software often fails to provide the available bandwidth
to the application. Although libraries and improved file-system interfaces can make
a significant improvement, we believe that fundamental changes are needed in the
file-server software. We propose a new technique, disk-directed I/O, that flips
the usual relationship between server and client to allow the disks (actually, disk
servers) to determine the flow of data for maximum performance. Our simulations
show that tremendous performance gains are possible. Indeed, disk-directed I/O provided
consistent high performance that was largely independent of data distribution, and
close to the maximum disk bandwidth.
}
comment = {
A shorter version of this paper appeared in OSDI, although this TR has more recent
numbers. The OSDI version is available here.
A more complete journal version is here.
The simulator software is also available..
}
}
@TechReport{Dartmouth:PCS-TR94-225,
author = {Christine McGavran },
title = {{Human Creativity Through Computer Gaming}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-225},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/112/TR94-225.pdf},
comment = {
A Senior Honors Thesis in Computer Science.
}
}
@TechReport{Dartmouth:PCS-TR94-224,
author = {Kristin Bruhl },
title = {{BMMC Permutations on a DECmpp 12000/sx 2000}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-224},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/111/TR94-224.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/111/TR94-224.pdf},
abstract = {
Increasingly, modern computing problems, including many scientific and business applications,
require huge amounts of data to be examined, modified, and stored. Parallel computers
can be used to decrease the time needed to operate on such large data sets, by allowing
computations to be performed on many pieces of data at once. For example, on the
DECmpp machine used in our research, there are 2048 processors in the parallel processor
array. The DECmpp can read data into each of these processors, perform a computation
in parallel on all of it, and write the data out again, theoretically decreasing
the execution time by a factor of 2048 over the time required by one of its processors.
Often, the computations that occur after the data is in the processors involve rearranging,
or permuting, the data within the array of parallel processors. Information moves
between processors by means of a network connecting them. Communication through
the network can be very expensive, especially if there are many collisions--simultaneous
contentions for the same network resource--between items of data moving from one
processor to another. When a program performs hundreds or even thousands of these
permutations during its execution, a bottleneck can occur, impeding the overall
performance of the program.
Effective algorithms that decrease the time required to permute the data within
a parallel computer can yield a significant speed increase in running programs with
large data sets. Cormen has designed algorithms to improve performance when the
data movement is defined by certain classes of permutations. This thesis will examine
the performance of one of these classes, the bit-matrix-multiply/complement (BMMC)
permutation, when implemented on the DECmpp. Although Cormen's algorithm was designed
for parallel disk systems, this thesis adapts it to permutations of data residing
in the memory of the parallel processors.
The DECmpp network follows the model of an Extended Delta Network (EDN). One characteristic
of an EDN is that it has a set of input and output ports to the network, each of
which can carry only one item of data at a time. If more than one item needs to
travel over a given port, a collision occurs. The data must access the port serially,
which slows down the entire operation. Cormen's algorithm reduces these collisions
by computing a schedule for sending the data over the network.
For small data sets, it is not worthwhile to perform the extra operations to generate
such a schedule, because the overhead associated with computing the schedule outweighs
the time gained by preventing collisions at the network ports. As the size of the
data set increases, eliminating collisions becomes more and more valuable. On the
DECmpp, when the data permutation involves more than 128 elements per processor,
our algorithm beats the more naive and obvious method for permuting in the parallel
processor array.
}
comment = {
A Senior Honors Thesis in Computer Science. Advisor: Thomas Cormen.
}
}
@TechReport{Dartmouth:PCS-TR94-223,
author = {Thomas H. Cormen and Thomas Sundquist and Leonard F. Wisniewski },
title = {{Asymptotically Tight Bounds for Performing BMMC Permutations on Parallel Disk Systems}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-223},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/110/TR94-223.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/110/TR94-223.pdf},
abstract = {
We give asymptotically equal lower and upper bounds for the number of parallel I/O
operations required to perform bit-matrix-multiply/complement (BMMC) permutations
on parallel disk systems. In a BMMC permutation on N records, where N is a power
of 2, each (lg N)-bit source address x maps to a corresponding (lg N)-bit target
address y by the matrix equation y = Ax XOR c, where matrix multiplication is performed
over GF(2). The characteristic matrix A is (lg N) x (lg N) and nonsingular over
GF(2). Under the Vitter-Shriver parallel-disk model with N records, D disks, B records
per block, and M records of memory, we show a universal lower bound of $Omega left(
frac{N}{BD} left( 1 + frac{rank{gamma}}{lg (M/B)} right) right)$ parallel I/Os for
performing a BMMC permutation, where gamma is the lower left (lg (N/B)) x (lg B)
submatrix of the characteristic matrix. We adapt this lower bound to show that the
algorithm for bit-permute/complement (BPC) permutations in Cormen93a is asymptotically
optimal. We also present an algorithm that uses at most $frac{2N}{BD} left( 4 ceil{frac{rank{gamma}}{lg
(M/B)}} + 4 right)$ parallel I/Os, which asymptotically matches the lower bound
and improves upon the BMMC algorithm in Cormen93a. When rank (gamma) is low, this
method is an improvement over the general-permutation bound of $Theta left( frac{N}{BD}
frac{lg (N/B)}{lg (M/B)} right)$.
We introduce a new subclass of BMMC permutations, called memory-load-dispersal (MLD)
permutations, which can be performed in one pass. This subclass, which is used in
the BMMC algorithm, extends the catalog of one-pass permutations appearing in Cormen93a.
Although many BMMC permutations of practical interest fall into subclasses that
might be explicitly invoked within the source code, we show how to detect in at
most $N/BD + ceil{frac{lg (N/B) + 1}{D}}$ parallel I/Os whether a given vector of
target addresses specifies a BMMC permutation. Thus, one can determine efficiently
at run time whether a permutation to be performed is BMMC and then avoid the general-permutation
algorithm and save parallel I/Os by using our algorithm.
}
}
@TechReport{Dartmouth:PCS-TR94-222,
author = {Dennis M. Healy and Sean S. B. Moore and Daniel N. Rockmore },
title = {{Efficiency and Stability Issues in the Numerical Computation of Fourier Transforms and Convolutions on the 2-Sphere}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-222},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/109/TR94-222.pdf},
}
@TechReport{Dartmouth:PCS-TR94-220,
author = {David Kotz and Song Bac Toh and Sriram Radhakrishnan },
title = {{A Detailed Simulation Model of the HP 97560 Disk Drive}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-220},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/108/TR94-220.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/108/TR94-220.pdf},
abstract = {
We implemented a detailed model of the HP 97560 disk drive, to replicate a model
devised by Ruemmler and Wilkes (both of Hewlett-Packard, HP). Our model simulates
one or more disk drives attached to one or more SCSI buses. The design is broken
into three components: a test driver, the disk model itself, and the discrete-event
simulation support. Thus, the disk model can be easily extracted and used in other
simulation environments. We validated our model using traces obtained from HP, using
the same "demerit" measure as Ruemmler and Wilkes. We obtained a demerit percentage
of 3.9%, indicating that our model was extremely accurate. This paper describes
our implementation, and is meant for those wishing to use our model, see our validation,
or understand our code.
}
comment = {
The software is available.
}
}
@TechReport{Dartmouth:PCS-TR94-219,
author = {James R. Driscoll and Dennis M. Healy and Daniel N. Rockmore },
title = {{Fast Spherical Transforms on Distance Transitive Graphs}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-219},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/107/TR94-219.pdf},
}
@TechReport{Dartmouth:PCS-TR94-218,
author = {James Gochee },
title = {{SPEDE: Simple Programming Environment for Distributed Execution}},
institution = {Dartmouth College, Computer Science,
address = {Hanover, NH},
number = {PCS-TR94-218},
year = {1994},
month = {January},
URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/106/TR94-218.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/106/TR94-218.pdf},
abstract = {
One of the main goals for people who use computer systems, particularly computational
scientists, is speed. In the quest for ways to make applications run faster, engineers
have developed parallel computers, which use more than one CPU to solve a task.
However, many institutions already posses significant computational power in networks
of workstations. Through software, it is possible to glue together clusters of machines
to simulate a parallel environment. SPEDE is one such system, designed to place
the potential of local machines at the fingertips of the programmer. Through a simple
interface, users design computational objects that can be linked and run in parallel.
The goal of the project is to have a small portable environment that allows various
types of computer systems to interact. SPEDE requires no altering of the kernel
and does not require system privileges to use. Using SPEDE, programmers can get
significant speedup for computationally intensive problems. As an example, a Mandelbrot
image generator was implemented, that attained a five-fold speedup with eight processors.
}
comment = {
A Senior Thesis in the Department of Math and Computer Science, Dartmouth College,
1992.
See also Technical Report PCS-TR94-217 for a user's manual for SPEDE. } } @TechReport{Dartmouth:PCS-TR94-217, author = {James Gochee }, title = {{SPEDE: A Simple Programming Environment for Distributed Execution (Users' Manual)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-217}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/105/TR94-217.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/105/TR94-217.pdf}, abstract = { Traditional single processor computers are quickly reaching their full computational potentials. The quest for faster and faster chips have brought technology to the point where the laws of physics are hampering future gains. Significant gains in speed must therefore come from using multiple processors instead of a single processor. This technology usually represents itself in the form of a parallel computer, such as the Connection Machine Model 5. Recently however, much interest has been focused on software that organizes single processor computers to behave like a parallel computer. This is desirable for sites which have large installations of workstations, since the cost of new parallel systems are prohibitive. SPEDE, a Simple Programming Environment for Distributed Execution, was designed for this purpose. It allows UNIX based machines of varying hardware types to be organized and utilized by a programmer of parallel applications. SPEDE is a user level system in that it requires no special privileges to run. Every user keeps a separate copy of the system so that security issues are covered by the normal UNIX operating environment. SPEDE is characterized as a large grained distributed environment. This means that applications which have a large processing to I/O ratio will be much more effective than those with a small ratio. SPEDE allows users to coordinate the use of many computers through a straightforward interface. Machines are organized by classes, which are terms that can be used to label and group them into more manageable units. For example, users might want to create a class based on the byte ordering of machines, or by their location. Users can then specify more completely which machines they want to use for a particular session. Sessions are essentially the interaction between objects in the SPEDE environment. A user creates an object to perform a certain task, such as constructing part of a fractal image. Objects can send and receive messages from other objects using a simple interface provided with SPEDE. Objects are machine independent, which means that the same object can be run simultaneously on different platforms. This is achieved by translating all messages into standard network byte ordering. However, if user data is being passed between objects, it is the user's responsibility to make sure byte ordering is correct. The SPEDE system involves several major components. These components help control and manage object interactions. Figure 1 shows a running session running with three machines (each surrounded by an oval rectangle). There are also three objects running, two named MandComp and one named Mand. Each object is on a different machine, although it is possible to have multiple objects on a single machine. In the figure, the lines connecting the various entities represent socket connections. UNIX sockets are the transport mechanism used in SPEDE, although one could implement a lower level protocol for more efficient communication. Sockets can also be a problem because some machines have strict limits on the number of connections a user can have open at any given time. } comment = { A Senior Thesis in the Department of Math and Computer Science, Dartmouth College, 1992.
See also Technical Report PCS-TR94-218 for a technical description of SPEDE. } } @TechReport{Dartmouth:PCS-TR94-216, author = {Perry Fizzano and Clifford Stein }, title = {{Scheduling in a Ring with Unit Capacity Links}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-216}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/104/TR94-216.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/104/TR94-216.pdf}, abstract = { We consider the problem of scheduling unit-sized jobs on a ring of processors with the objective of minimizing the completion time of the last job. Unlike much previous work we place restrictions on the capacity of the network links connecting processors. We give a polynomial time centralized algorithm that produces optimal length schedules. We also give a simple distributed 2-approximation algorithm. } } @TechReport{Dartmouth:PCS-TR94-215, author = {Matthew T. Dickerson and Robert L. Scot Drysdale and Scott A. McElfresh and Emo Welzl }, title = {{Fast Greedy Triangulation Algorithms}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-215}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/103/TR94-215.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/103/TR94-215.pdf}, abstract = { The greedy triangulation of a set $S$ of $n$ points in the plane is the triangulation obtained by starting with the empty set and at each step adding the shortest compatible edge between two of the points, where a compatible edge is defined to be an edge that crosses none of the previously added edges. In this paper we present a simple, practical algorithm that computes the greedy triangulation in expected time $O(n log n)$ and space $O(n)$ for points uniformly distributed over any convex shape. A variant of this algorithm should be fast for some other distributions. As part of this algorithm we give an edge compatiblity test that requires $O(n)$ time for both tests and updates to the underlying data structure. We also prove properties about the expected lengths of edges in greedy and Delaunay triangulations of uniformly distributed points. } } @TechReport{Dartmouth:PCS-TR94-214, author = {Chris Armen and Clifford Stein }, title = {{A 2-3/4-Approximation Algorithm for the Shortest Superstring Problem}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-214}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/102/TR94-214.pdf}, abstract = { Given a collection of strings S={s_1,...,s_n} over an alphabet Sigma, a superstring alpha of S is a string containing each s_i as a substring, that is, for each i, 1<=i<=n, alpha contains a block of |s_i| consecutive characters that match s_i exactly. The shortest superstring problem is the problem of finding a superstring alpha of minimum length. The shortest superstring problem has applications in both computational biology and data compression. The problem is NP-hard [GallantMS80]; in fact, it was recently shown to be MAX SNP-hard [BlumJLTY91]. Given the importance of the applications, several heuristics and approximation algorithms have been proposed. Constant factor approximation algorithms have been given in [BlumJLTY91] (factor of 3), [TengY93] (factor of 2-8/9), [CzumajGPR94] (factor of 2-5/6) and [KosarajuPS94] (factor of 2-50/63). Informally, the key to any algorithm for the shortest superstring problem is to identify sets of strings with large amounts of similarity, or overlap. While the previous algorithms and their analyses have grown increasingly sophisticated, they reveal remarkably little about the structure of strings with large amounts of overlap. In this sense, they are solving a more general problem than the one at hand. In this paper, we study the structure of strings with large amounts of overlap and use our understanding to give an algorithm that finds a superstring whose length is no more than 2-3/4 times that of the optimal superstring. We prove several interesting properties about short periodic strings, allowing us to answer questions of the following form: given a string with some periodic structure, characterize all the possible periodic strings that can have a large amount of overlap with the first string. } } @TechReport{Dartmouth:PCS-TR94-213, author = {Perry Fizzano and Clifford Stein and David R. Karger and Joel Wein }, title = {{Job Scheduling in Rings}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-213}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/101/TR94-213.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/101/TR94-213.pdf}, abstract = { We give distributed approximation algorithms for job scheduling in a ring architecture. In contrast to almost all other parallel scheduling models, the model we consider captures the influence of the underlying communications network by specifying that task migration from one processor to another takes time proportional to the distance between those two processors in the network. As a result, our algorithms must balance both computational load and communication time. The algorithms are simple, require no global control, and work in a variety of settings. All come with small constant-factor approximation guarantees; the basic algorithm yields schedules of length at most 4.22 times optimal. We also give a lower bound on the performance of any distributed algorithm some results for a simple capacitated case, and the results of simulation experiments, which give better results than our worst-case analysis. } } @TechReport{Dartmouth:PCS-TR94-211, author = {David Kotz and Nils Nieuwejaar }, title = {{Dynamic File-Access Characteristics of a Production Parallel Scientific Workload}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-211}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/100/TR94-211.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/100/TR94-211.pdf}, abstract = { Multiprocessors have permitted astounding increases in computational performance, but many cannot meet the intense I/O requirements of some scientific applications. An important component of any solution to this I/O bottleneck is a parallel file system that can provide high-bandwidth access to tremendous amounts of data in parallel to hundreds or thousands of processors. Most successful systems are based on a solid understanding of the characteristics of the expected workload, but until now there have been no comprehensive workload characterizations of multiprocessor file systems. We began the CHARISMA project in an attempt to fill that gap. We instrumented the common node library on the iPSC/860 at NASA Ames to record all file-related activity over a two-week period. Our instrumentation is different from previous efforts in that it collects information about every read and write request and about the mix of jobs running in the machine (rather than from selected applications). The trace analysis in this paper leads to many recommendations for designers of multiprocessor file systems. First, the file system should support simultaneous access to many different files by many jobs. Second, it should expect to see many small requests, predominantly sequential and regular access patterns (although of a different form than in uniprocessors), little or no concurrent file-sharing between jobs, significant byte- and block-sharing between processes within jobs, and strong interprocess locality. Third, our trace-driven simulations showed that these characteristics led to great success in caching, both at the compute nodes and at the I/O nodes. Finally, we recommend supporting strided I/O requests in the file-system interface, to reduce overhead and allow more performance optimization by the file system. } comment = { TR94-230 is related. } } @TechReport{Dartmouth:PCS-TR94-209, author = {J. Matthews and F. Makedon and P. Gloor }, title = {{Videoscheme: A Research, Authoring, and Teaching Tool for Multimedia}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-209}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/99/TR94-209.pdf}, abstract = { The availability of digital multimedia technology poses new challenges to researchers, authors, and educators, even as it creates new opportunities for rich communication. This paper suggests interactive computer programming as a fruitful approach to these challenges. VideoScheme, a prototype video programming environment, is described along with promising applications. } } @TechReport{Dartmouth:PCS-TR94-208, author = {M. Cheyney and P. Gloor and D. B. Johnson and F. Makedon and J. Matthews and P. Metaxas }, title = {{Conference on a Disk: A Successful Experiment in Hypermedia Publishing (Extended Abstract)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-208}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/98/TR94-208.pdf}, abstract = { Academic conferences are a long-standing and effective form of multimedia communication. Conference participants can transmit and recieve information through sight, speech, gesture, text, and touch. This same-time, same-place communication is sufficiently valuable to justify large investments in time and travel funds. Printed conference proceedings are attempts to recapture the value of a life conference, but they are limited by a fragmented and inefficient approach to the problem. We addressed this problem in the multimedia proceedings of the DAGS'92 conference. The recently published CD-ROM delibers text, graphic, audio, and video information as an integrated whole, with extensive provisions for random access and hypermedia linking. We belive that this project provides a model for future conference publications and highlights some of the research issues that must be resolved before similar publications can be quickly and inexpensively produced. } } @TechReport{Dartmouth:PCS-TR94-207, author = {Fillia Makedon and Samuel A. Rebelsky and Matthew Cheyney and Charles B. Owen and Peter A. Gloor }, title = {{Issues and Obstacles with Multimedia Authoring}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-207}, year = {1995}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/97/TR94-207.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/97/TR94-207.pdf}, abstract = { Unlike traditional authoring, multimedia authoring involves making hard choices, forecasting technological evolution and adapting to software and hardware technology changes. It is, perhaps, an unstable field of endeavor for an academic to be in. Yet, it is important that academics are, in fact, part of this process. This paper discusses some of the common threads shared by three dissimilar cases of multimedia authoring which we have experimented with, that of multimedia conference proceedings, multimedia courseware development and multimedia information kiosks. We consider these applications from an academic point of view and review the benefits and pitfalls of academic development while sharing points of hard-learned wisdom. We draw on experiences from some of the projects run at the Dartmouth Experimental Visualization Laboratory (DEVlab), where we have been developing different types of multimedia applications. } comment = { Invited Presentation, EdMedia '94 Vancouver, Canada. Also published in the EdMedia'94 conference proceedings. This Technical Report has occasionally been listed (accidentally) as TR95-256. TR94-207 is the correct number. } } @TechReport{Dartmouth:PCS-TR94-206, author = {Dimitrios Kavvadias and Grammati E. Pantziou and Paul G. Spirakis and Christos D. Zaroliagis }, title = {{Efficient Sequential and Parallel Algorithms for the Negative Cycle Problem}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-206}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/96/TR94-206.pdf}, abstract = { We present here an algorithm for detecting (and outputting, if exists) a negative cycle in an $n$-vertex planar digraph $G$ with real edge weights. Its running time ranges from $O(n)$ up to $O(n^{1.5}log n)$ as a certain topological measure of $G$ varies from $1$ up to $Theta(n)$. Moreover, an efficient CREW PRAM implementation is given. Our algorithm applies also to digraphs whose genus $gamma$ is $o(n)$. } } @TechReport{Dartmouth:PCS-TR94-204, author = {Dimitrios Kagaris and Grammati E. Pantziou and Spyros Tragoudas and Christos D. Zaroliagis }, title = {{Quickest Paths: Faster Algorithms and Dynamization}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR94-204}, year = {1994}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/95/TR94-204.pdf}, abstract = { Given a network $N=(V,E,{c},{l})$, where $G=(V,E)$, $|V|=n$ and $|E|=m$, is a directed graph, ${c}(e) > 0$ is the capacity and ${l}(e) ge 0$ is the lead time (or delay) for each edge $ein E$, the quickest path problem is to find a path for a given source--destination pair such that the total lead time plus the inverse of the minimum edge capacity of the path is minimal. The problem has applications to fast data transmissions in communication networks. The best previous algorithm for the single--pair quickest path problem runs in time $O(r m+r n log n)$, where $r$ is the number of distinct capacities of $N$ cite{ROS}. In this paper, we present algorithms for general, sparse and planar networks that have significantly lower running times. For general networks, we show that the time complexity can be reduced to $O(r^{ast} m+r^{ast} n log n)$, where $r^{ast}$ is at most the number of capacities greater than the capacity of the shortest (with respect to lead time) path in $N$. For sparse networks, we present an algorithm with time complexity $O(n log n + r^{ast} n + r^{ast} tilde{gamma} log tilde{gamma})$, where $tilde{gamma}$ is a topological measure of $N$. Since for sparse networks $tilde{gamma}$ ranges from $1$ up to $Theta(n)$, this constitutes an improvement over the previously known bound of $O(r n log n)$ in all cases that $tilde{gamma}=o(n)$. For planar networks, the complexity becomes $O(n log n + nlog^3 tilde{gamma}+ r^{ast} tilde{gamma})$. Similar improvements are obtained for the all--pairs quickest path problem. We also give the first algorithm for solving the dynamic quickest path problem. } } @TechReport{Dartmouth:PCS-TR93-202, author = {Panagiotis Metaxas and Grammati E. Pantziou and Antonios Symvonis }, title = {{Parallel h-v Drawings of Binary Trees}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-202}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/94/TR93-202.pdf}, abstract = { In this paper we present a method to obtain optimal h-v and inclusion drawings in parallel. Based on parallel tree contraction, our method computes optimal (with respect to a class of cost functions of the enclosing rectangle) drawings in $O(log^2 n)$ parallel time by using a polynomial number of EREW processors. The number of processors reduces substantially when we study minimum area drawings. The method can be extended to compute optimal inclusion layouts in the case where each leaf $l$ of the tree is represented by rectangle $l_x times l_y$ (the dimensions of which are part of the input). For polynomial area layouts, our work places the problem of obtaining optimal size h-v or inclusion drawings in NC, presenting the first algorithm with polylogarithmic time complexity. Our method also yields an NC algorithm for the slicing floorplanning problem. Whether this problems was in NC was an open question~cite{CT90}. } } @TechReport{Dartmouth:PCS-TR93-201, author = {Grammati E. Pantziou and Paul G. Spirakis and Christos D. Zaroliagis }, title = {{Parallel Max Cut Approximations}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-201}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/93/TR93-201.pdf}, abstract = { Given a graph with positive integer edge weights one may ask whether there exists an edge cut whose weight is bigger than a given number. This problem is NP-complete. We present here an approximation algorithm in NC which provides tight upper bounds to the proportion of edge cuts whose size is bigger than a given number. Our technique is based on the methods to convert randomized parallel algorithms into deterministic ones introduced by Karp and Wigderson. The basic idea of those methods is to replace an exponentially large sample space by one of polynomial size. In this work, we prove the interesting result that the statistical distance of random variables of the small sample space is bigger than the statistical distance of corresponding variables of the exponentially large space, which is the space of all edge cuts taken equiprobably. } } @TechReport{Dartmouth:PCS-TR93-200, author = {Hristo N. Djidjev and Grammati E. Pantziou and Christos D. Zaroliagis }, title = {{On-Line and Dynamic Shortest Paths Through Graph Decompositions}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-200}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/92/TR93-200.pdf}, abstract = { We describe algorithms for finding shortest paths and distances in a planar digraph which exploit the particular topology of the input graph. An important feature of our algorithms is that they can work in a dynamic environment, where the cost of any edge can be changed or the edge can be deleted. For outerplanar digraphs, for instance, the data structures can be updated after any such change in only $O(log n)$ time, where $n$ is the number of vertices of the digraph. We also describe the first parallel algorithms for solving the dynamic version of the shortest path problem. Our results can be extended to hold for digraphs of genus $o(n)$. } } @TechReport{Dartmouth:PCS-TR93-198, author = {David Kotz and Preston Crow }, title = {{The Expected Lifetime of "Single-Address-Space" Operating Systems}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-198}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/91/TR93-198.ps.Z}, abstract = { Trends toward shared-memory programming paradigms, large (64-bit) address spaces, and memory-mapped files have led some to propose the use of a single virtual-address space, shared by all processes and processors. Typical proposals require the single address space to contain all process-private data, shared data, and stored files. To simplify management of an address space where stale pointers make it difficult to re-use addresses, some have claimed that a 64-bit address space is sufficiently large that there is no need to ever re-use addresses. Unfortunately, there has been no data to either support or refute these claims, or to aid in the design of appropriate address-space management policies. In this paper, we present the results of extensive kernel-level tracing of the workstations in our department, and discuss the implications for single-address-space operating systems. We found that single-address-space systems will not outgrow the available address space, but only if reasonable space-allocation policies are used, and only if the system can adapt as larger address spaces become available. } comment = { The on-line version is a revision of March 15, 1996. An earlier revised version appeared in SIGMETRICS '94. The original technical report is not available on-line. } } @TechReport{Dartmouth:PCS-TR93-196, author = {Tim Olson and Joe Destefano }, title = {{Wavelet Localization of the Radon Transform}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-196}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/90/TR93-196.pdf}, } @TechReport{Dartmouth:PCS-TR93-194, author = {Thomas H. Cormen }, title = {{Vector Layout in Virtual-Memory Systems for Data-Parallel Computing}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-194}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/89/TR93-194.pdf}, } @TechReport{Dartmouth:PCS-TR93-193, author = {Thomas H. Cormen and Leonard F. Wisniewski }, title = {{Asymptotically Tight Bounds for Performing BMMC Permutations on Parallel Disk Systems}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-193}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/88/TR93-193.pdf, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/88/TR93-193.ps.Z}, comment = { This TR is superceded by TR94-223. } } @TechReport{Dartmouth:PCS-TR93-192, author = {Berrin A. Yanikoglu and Peter A. Sandon }, title = {{Off-line Cursive Handwriting Recognition Using Style Parameters}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-192}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/87/TR93-192.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/87/TR93-192.pdf}, abstract = { (No abstract available). } } @TechReport{Dartmouth:PCS-TR93-191, author = {Jerome L. Quinn }, title = {{Accurate Verification of Five-Axis Numerically Controlled Machining}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-191}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/86/TR93-191.pdf}, } @TechReport{Dartmouth:PCS-TR93-190, author = {David Kotz }, title = {{Throughput of Existing Multiprocessor File Systems (An Informal Study)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-190}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/85/TR93-190.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/85/TR93-190.pdf}, abstract = { Fast file systems are critical for high-performance scientific computing, since many scientific applications have tremendous I/O requirements. Many parallel supercomputers have only recently obtained fully parallel I/O architectures and file systems, which are necessary for scalable I/O performance. Scalability aside, I show here that many systems lack sufficient absolute performance. I do this by surveying the performance reported in the literature, summarized in an informal table. } } @TechReport{Dartmouth:PCS-TR93-189, author = {J. Diaz and A. Gibbons and Grammati E. Pantziou and M. Serna and Paul G. Spirakis and J. Toran }, title = {{Efficient Parallel Algorithms for some Tree Layout Problems}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-189}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/84/TR93-189.pdf}, abstract = { The minimum cut and minimum length linear arrangement problems usually occur in solving wiring problems and have a lot in common with job sequencing questions. Both problems are NP-complete for general graphs and in P for trees. We present here two algorithms in NC. The first solves the minimum length linear arrangement problem for unrooted trees in $O(log^2 n)$ time and $O(n^2 3^{log n})$ CREW PRAM processors. The second algorithm solves the minimum cut arrangement for unrooted trees of maximum degree $d$ in $O(d log^2 n)$ time and $O(n^2 /log n)$ CREW PRAM processors. } } @TechReport{Dartmouth:PCS-TR93-188, author = {Thomas H. Cormen and David Kotz }, title = {{Integrating Theory and Practice in Parallel File Systems}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-188}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/83/TR93-188-update.ps.Z, http://www.cs.dartmouth.edu/cms_file/SYS_techReport/83/TR93-188-update.pdf}, abstract = { Several algorithms for parallel disk systems have appeared in the literature recently, and they are asymptotically optimal in terms of the number of disk accesses. Scalable systems with parallel disks must be able to run these algorithms. We present a list of capabilities that must be provided by the system to support these optimal algorithms: control over declustering, querying about the configuration, independent I/O, turning off file caching and prefetching, and bypassing parity. We summarize recent theoretical and empirical work that justifies the need for these capabilities. } comment = { The original 1993 tech report was superceded by the conference version. The paper has since been revised, re-issued on 9/20/94 as an updated technical report. } } @TechReport{Dartmouth:PCS-TR93-187, author = {James Matthews and Peter A. Gloor and Fillia Makedon }, title = {{VideoScheme: A Programmable Video Editing System for Automation and Media Recognition}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR93-187}, year = {1993}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/82/TR93-187.pdf}, abstract = { The recent development of powerful, inexpensive hardware and software support had made digital video editing possible on personal computers and workstations. To date the video editing application category has been dominated by visual, easy-to-use, direct manipulation interfaces. These systems bring high-bandwidth human-computer interaction to a task formerly characterized by slow, inflexible, indirectly-operated machines. However, the direct manipulation computer interfaces are limited by their manual nature, and can not easily accommodate algorithmically- defined operations. This paper proposes a melding of the common direct manipulation interfaces with a programming language which we have enhanced to manipulate digital audio and video. The result is a system which can automate routine tasks as well as perform tasks based on sophisticated media recognition algorithms. } } @TechReport{Dartmouth:PCS-TR92-186, author = {Deb Banerjee }, title = {{Formal Implementation of High-Level Languages for Data-Parallel Programming}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-186}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/81/TR92-186.pdf}, abstract = { The success of parallel architectures has been limited by the lack of high-level parallel programming languages and useful programming models. The data-parallel model of programming has been demonstrated to be useful and natural on a wide variet of parallel architectures. This dissertation presents a set of formal techniques for compiling high- level languages based on data-parallelism. } } @TechReport{Dartmouth:PCS-TR92-185, author = {Peter Su }, title = {{Algorithms for Closest Point Problems: Practice and Theory}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-185}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/80/TR92-185.pdf}, abstract = { This paper describes and evaluates know sequential algorithms for constructing planar Voronoi diagrams and Delaunay triangulations. In addition, it describes a new incremental algorithm which is simple to understand and implement, but whose performance is competitive with all known methods. The experiments in this paper are more than just simple benchmarks, they evaluate the expected performance of the algorithms in a precise and machine independent fashion. Thus, the paper also illustrates how to use experimental tools to both understand the behaviour of different algorithms and to guide the algorithm design process. } } @TechReport{Dartmouth:PCS-TR92-184, author = {Peter Su and Robert L. Scot Drysdale }, title = {{Building Segment Trees in Parallel}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-184}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/79/TR92-184.pdf}, abstract = { The segment tree is a simple and important data structure in computational geometry [7,11]. We present an experimental study of parallel algorithms for building segment trees. We analyze the algorithms in the context of both the PRAM (Parallel Random Access Machine) and hypercube architectures. In addition, we present performance data for implementations developed on the Connection Machine. We compare two different parallel alforitms, and we also compare our parallel algorithms to a good sequential algorithm for doing the same job. In this way, we evaluate the overall efficiency of our parallel methods. Our performance results illustrates the problems involved in using popular machine models(PRAM) and analysis techniques (asymptotic efficiency) to predict the performance of parallel algorithms on real machines. We present two different analyses of our algorithms and show that neither is effective in predicting the actual performance numbers that we obtained. } } @TechReport{Dartmouth:PCS-TR92-183, author = {Peter Su }, title = {{Concurrent Local Search for Fast Proximity Algorithms on Parallel and Vector Architectures}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-183}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/78/TR92-183.pdf}, abstract = { This paper presents a fast algorithm for solving the all-nearest-neighbors problem. The algorithm uses a data parallel style of programming which can be efficiently utilized on a variety of parallel and vector architectures [4,21,26]. I have implemented the algorithm in C on one such architecture, the Cray Y-MP. On one Cray CPU, the implementation is about 19 times faster than a fast sequential algorithm running on a Sparc workstation. The main idea in the algorithm is to divide the plane up into a fixed grid of cells, or buckets. When the points are well distributed, the algorithm processes each query point, q, by searching a small number of cells close to q. Bentley, WEide and Yao first presented this idea for conventional architectures [3], but the technique works equally well on parallel and vector machines, leading to a simple, efficient algorithm. We can also use the cell technique to solve a wide variety of basic computational problems such as finding closest pairs, sorting and constructing Voronoi diagrams and Delaunay triangulations. } } @TechReport{Dartmouth:PCS-TR92-182, author = {Peter Su and Matt Bishop }, title = {{How to Encrypt /usr/dict/words in About a Second}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-182}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/77/TR92-182.pdf}, abstract = { We present an implementation of the Data Encryption Standard on the Connection Machine architecture. The DES encryption algorithm is ideally suited to the Connection Machine because it consists of bit serial operations, and thousands of encryptions can be done in parallel, independently of one another. Thus, our code encrypts passwords about ten times faster than the fastest competition that we know about. In addition, the nature of the Connection Machine's architecture is such that some of the optimizations that make DES run much faster on conventional architectures have no effect on the performance of the Connection Machine. Our comparison of a simple implementation along with one that uses many optimizations illustrates this fact. } } @TechReport{Dartmouth:PCS-TR92-181, author = {Glenn Hurlbert and Garth Isaak }, title = {{On The De Bruijn Torus Problem}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-181}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/76/TR92-181.pdf}, abstract = { A (kn;n)k-de Bruijn Cycle is a cyclic k-ary sequence with the property that every k-ary n-tuple appears exactly once contiguously on the cycle. A (kr, ks; m, n)k-de Bruijn Torus is a k-ary krXks toroidal array with the property that every k-ary m x n matrix appears exactly once contiguously on the torus. As is the case with de Bruijn cycles, the 2-dimensional version has many interesting applications, from coding and communications to pseudo-random arrays, spectral imaging, and robot self-location. J.C. Cock proved the existence of such tori for all m, n, and k, and Chung, Diaconis, and Graham asked if it were possible that r = s and m -= n for n even. Fan, Fan, Ma and Siu showed this was possible for k - 2. Combining new techniques with old, we prove the result for k > 2 and show that actually much more is possible. The cases in 3 or more dimensions remain. } } @TechReport{Dartmouth:PCS-TR92-180, author = {Peter A. Gloor and Donald B. Johnson and Fillia Makedon and Panagiotis Metaxas }, title = {{A Visualization System for Correctness Proofs of Graph Algorithms}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-180}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/75/TR92-180.pdf}, abstract = { In this paper we describe a system for visualizing correctness proofs of graph algorithms. The system has been demonstrated for a greedy algorithm. Prims algorithm for finding a minimum spanning tree of an undirected, weighted graph. We believe that our system is particularly appropriate for greedy algorithms, though much of what we discuss can guide visualization of proofs in other contexts. While an example is not a proof, our system provides concrete examples to illustrate the operation of the algorithm. These examples can be referred to by the user interactively and alternatively with the visualization of the proof where the general case is portrayed abstractly. } } @TechReport{Dartmouth:PCS-TR92-179, author = {David Kotz }, title = {{Multiprocessor File System Interfaces}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-179}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/74/TR92-179.ps.Z}, abstract = { Increasingly, file systems for multiprocessors are designed with parallel access to multiple disks, to keep I/O from becoming a serious bottleneck for parallel applications. Although file system software can transparently provide high-performance access to parallel disks, a new file system interface is needed to facilitate parallel access to a file from a parallel application. We describe the difficulties faced when using the conventional (Unix-like) interface in parallel applications, and then outline ways to extend the conventional interface to provide convenient access to the file for parallel programs, while retaining the traditional interface for programs that have no need for explicitly parallel file access. Our interface includes a single naming scheme, a multiopen operation, local and global file pointers, mapped file pointers, logical records, multifiles, and logical coercion for backward compatibility. } } @TechReport{Dartmouth:PCS-TR92-178, author = {Panagiotis Metaxas }, title = {{Parallel Algorithms For Graph Problems (Thesis)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-178}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/73/TR92-178.pdf}, abstract = { In this thesis we examine three problems in graph theory and propose efficient parallel algorithms for solving them. We also introduce a number of parallel algorithmic techniques. } } @TechReport{Dartmouth:PCS-TR92-177, author = {Barry F. Schaudt }, title = {{Multiplicatively Weighted Crystal Growth Voronoi Diagrams (Thesis)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-177}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/72/TR92-177.pdf}, abstract = { Voronoi diagrams and variants of Voronoi diagrams have been used for many years to model crystal growth. If the boundary of the growing crystals are circular and all the crystals start at the same time and have the same constant growth rate, then the Voronoi diagram is used to model the growth. If the crystals start at different times, the additively weighted Voronoi diagram is used to model the crystal growth. In this thesis, I propose a new type of Voronoi diagram called the multiplicatively weighted crystal growth Voronoi diagram, that can be used to model crystal growth when the crystals have different constant growth rates. In this new model, the distance from a site to a point in its region is measured along a shortest path lying entirely within the region. In the multiplicatively weighted crystal growth Voronoi diagram, a growing crystal (or region) may "wrap around" another site's region. When a region wraps around, distances from the site are in part measured along the boundary of the two regions, treating one of the regions as an obstacle, rather than along a straight line that passes through the region. The worst case size of the multiplicatively weighted crystal growth Voronoi, diagram is 0(n 2). To construct the diagram, techniques from numerical analysis are used to approximate and to intersect curves described by a system of first order differential equations. Numerical methods to approximated a curve construct a polygonal approximation of the curve. One step of the numerical methods constructs an edge of the polygonal approximation. In the new Voronoi diagram, a step may require 0(n ) constant time operations. Let S be the number of steps required by the numerical method used just to draw the diagram. In the worst case, the algorithm presented in this thesis requires O (n 3) intersection calculations plus O (nS lg S ) time using O (n 3 + S ) space. A variant of this algorithm requires O (n 3) intersection calculations plus O (nS 2 + n 2S ) time using O (n 2) space. Also presented are some variants of the new Voronoi diagram. One of these variants uses a convex polygon distance function. The multiplicatively weighted crystal growth Voronoi diagram using a convex polygon distance function does not require numerical methods to construct. } } @TechReport{Dartmouth:PCS-TR92-176, author = {David Kotz and Fillia Makedon and Matt Bishop and Robert L. Scot Drysdale and Donald B. Johnson and Panagiotis Metaxas }, title = {{Parallel Computer Needs at Dartmouth College}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR92-176}, year = {1992}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/71/TR92-176.ps.Z}, abstract = { To determine the need for a parallel computer on campus, a committee of the Graduate Program in Computer Science surveyed selected Dartmouth College faculty and students in December, 1991, and January, 1992. We hope that the information in this report can be used by many groups on campus, including the Computer Science graduate program and DAGS summer institute, Kiewit's NH Supercomputer Initiative, and by numerous researchers hoping to collaborate with people in other disciplines. We found significant interest in parallel supercomputing on campus. An on-campus parallel supercomputing facility would not only support numerous courses and research projects, but would provide a locus for intellectual activity in parallel computing, encouraging interdisciplinary collaboration. We believe that this report is a first step in that direction. } } @TechReport{Dartmouth:PCS-TR91-174, author = {Fillia Makedon and Antonios Symvonis }, title = {{Optimal Algorithms for Multipacket Routing Problems on Rings}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-174}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/70/TR91-174.pdf}, abstract = { We study multipacket routing problems. We divide the multipacket routing problem into two classes, namely, distance limited and bisection limited routing problems. Then, we concentrate on rings of processors. We prove a new lower bound of 2n/ 3 routing steps for the case of distance limited routing problems. We also give an algorithm that tightens this lower bound. For bisection limited problems the lower bound is kn/ 4,k >2, where k is the number of packets per processor. The trivial algorithm needs in the worst case k | n /2| steps to terminate. An algorithm that completes the routing in kn /4 + 2.5 n routing steps is given. We define the class of pure routing algorithms and we demonstrate that new lower bounds hold if the routing is to be done by an algorithm in this class. } } @TechReport{Dartmouth:PCS-TR91-169, author = {Donald B. Johnson and Larry Raab }, title = {{Effects of Replication on the Duration of Failure in Distributed Databases}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-169}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/69/TR91-169.pdf}, abstract = { Replicating data objects has been suggested as a means of increasing the performance of a distributed database system in a network subject to link and site failures. Since a network may partition as a consequence of such failures, a data object may become unavailable from a given site for some period of time. In this paper we study duration failure, which we define as the length of time, once the object becomes unavailable from a particular site, that the object remains unavailable. We show that, for networks composed of highly-reliable components, replication does not substantially reduce the duration of failure. We model a network as a collection of sites and links, each failing and recovering independently according to a Poisson process. Using this model, we demonstrate via simulation that the duration of failure incurred using a non-replicated data object is nearly as short as that incurred using a replicated object and a replication control protocol, including an unrealizable protocol which is optimal with respect to availability. We then examine analytically a simplified system in which the sites but not the links are subject to failure. We prove that if each site operates with probability p, then the optimal replication protocol, Available Copies [5,26], reduces the duration of failure by at most a factor of 1-p/1+p. Lastly, we present bounds for general systems, those in which both the sites and the communications between the sites may fail. We prove, for example, that if sites are 95% reliable and a communications failure is sufficiently short (either infallible or satisfying a function specified in the paper) then replication can improve the duration of failure by at most 2.7% of that experienced using a single copy. These results show that replication has only a small effect of the duration of failure in present-day partitionable networks comprised of realistically reliable components. } } @TechReport{Dartmouth:PCS-TR91-168, author = {Donald B. Johnson and Larry Raab }, title = {{Availability Issues in Data Replication in Distributed Database}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-168}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/68/TR91-168.pdf}, abstract = { Replication of data at more than one site in a distributed database has been reported to increase the availability in data in systems where sites and links are subject to failure. We have shown in results summarized in this paper that in many interesting cases the advantage is slight. A well-placed single copy is available to transactions almost as much of the time as is correct replicated data no matter how ingeniously it is managed. We explain these findings in terms of the behavior of the partitions that form in networks where components fail. We also show that known and rather simple protocols for the maintenance of multiple copies are essentially best possible by comparing them against an unrealizable "protocol" that knows the future. We complete our study of these questions by reporting that while computing the availability of data is #P-complete, nonetheless there is a tight analytical bound on the amount replication can improve over a well-located single copy. We close with some observations regarding system design motivated by this work. } } @TechReport{Dartmouth:PCS-TR91-167, author = {Donald B. Johnson and Larry Raab }, title = {{Complexity of Network Reliability and Optimal Database Placement Problems}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-167}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/67/TR91-167.pdf}, abstract = { A fundamental problem of distributed database design in an existing network where components can fail is finding an optimal location at which to place the database in a centralized system or copies of each data item in a decentralized or replicated system. In this paper it is proved for the first time exactly how hard this placement problem is under the measure of data availability. Specifically, we show that the optimal placement problem for availability is #P- complete, a measure of intractability at least as severe as NP-completeness. Given the anticipated computational difficulty of finding an exact solution, we go on to describe an effective, practical method for approximating the optimal copy placement. To obtain these results, we model the environment in which a distributed database operates by a probabilistic graph, which is a set of fully-reliable vertices representing sites, and a set of edges representing communication links, each operational with a rational probability. We prove that finding the optimal copy placement in a probabilistic graph is #P-complete by giving a sequence of reductions from #Satisfiability. We generalize this result to networks in which each site and each link has an independent, rational operational probability and to networks in which all the sites or all the links have a fixed, uniform operational probabilities. } } @TechReport{Dartmouth:PCS-TR91-166, author = {Donald B. Johnson and Panagiotis Metaxas }, title = {{A Parallel Algorithm for the Minimum Spanning Tree}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-166}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/66/TR91-166.pdf}, } @TechReport{Dartmouth:PCS-TR91-165, author = {Jill P. David and Julie C. Jumes and Fillia Makedon }, title = {{An Object-Oriented Learning/Design Support Environment}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-165}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/65/TR91-165.pdf}, abstract = { We present an object-oriented experimental learning and design support environment, call AVT, for an Algorithm Visualization Tool, implemented in Digitalk's Smalltalk/V1 on a Macintosh II2, AVT provides a domain- independent visualization tool, an exploratory learning environment, and an experimental heuristic design environment. Algorithm visualization is the exploration of ways to visualize intuitively the computational behavior of an algorithm using multiple views, some of which are visual in the graphical sense [2,4]. AVT employs other views (combining text and graphics) to explain the problem, the strategy, the heuristics, and the reasoning process behind the solutions. User interaction in AVT includes not only passive viewingof the animated algorithmic process but also active participation in the design of the steps of the algorithm. Object-Oriented Programming(OOP)offers an attractive paradigm for rapidly implementing heuristics as well as more coherent and understandable code [1,12]. Inheritance properties of OOP languages capture natural mechanisms such as specialization, abstraction, and evolution allowing us to model our environment in a more natural manner[11]. } } @TechReport{Dartmouth:PCS-TR91-164, author = {Otto Mayer and Graham E. Oberem and Fillia Makedon }, title = {{Ilona: An advanced CAI Tutorial System for the Fundamentals of Logic}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-164}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/64/TR91-164.pdf}, abstract = { An advanced tutorial system for teaching the fundamentals of logic has been developed to run on UNIX work stations and commonly available micro-computers. An important part of this tutorial is the intelligent problem solving environment which allows students to practise wiriting logical sentences in mathematical notation. A natural language system for intelligent logic narrative analysis (ILONA) allows students to type in their own logical sentences in plain English and then have the computer check their working when they write these in mathematical form. ILONA is an intelligent tutoring system which allows students a great deal of initiative in problem solving and provides a degree of flexibility in answer evaluation not found in traditional CAI systems. The concepts and structures used in the development of ILONA are easily transferable to other domains. } } @TechReport{Dartmouth:PCS-TR91-163, author = {Fillia Makedon and Adononios Simvonis }, title = {{Multipacket Routing on Rings}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-163}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/63/TR91-163.pdf}, abstract = { We study multipacket routing problems. We divide the multipacket routing problem into two classes, namely, distance limited and bisection limited routing problems. Then, we concentrate on rings of processors. Having a full understanding of the multipacket routing problem on rings is essential before trying to attack the problem for the more general case of r-dimensional meshes and tori. We prove a new lower bound of 2n/3 routing steps for the case of distance limited routing problems. We also give an algorithm that tightens this lower bound. For bisection limited problems, we present an algorithm that completes the routing in near optimal time. } } @TechReport{Dartmouth:PCS-TR91-162, author = {Dimitrios Kagaris and Fillia Makedon }, title = {{A Metric Towards Efficient Exhaustive Test Pattern Generation}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-162}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/62/TR91-162.pdf}, abstract = { A viable technique [7] in built-in self-test (BIST)[2] is to generate test patterns pseudo-exhaustively by using linear feedback shift registers (LFSR's). The goal is to find an appropriate primitive polynomial of degree d that will generat 2d test patterns in order to exercise all circuit outputs simultaneously. In an attempt to reduce the degree d of the polynomial the following strategy was proposed in [6,5]. In the first phase, partition the circuit into segments by inserting a small number of register cells, so that the input dependency of any circuit element in the segments is no more than d. Then, obain an appropriate primitive polynomial of degree d by inserting additional register cells. In [12] we have proposed a heuristic for phase one that does not necessarily partition the circuit. Extensive experimentation has shown that this results in a considerably smaller cell overhead. In this paper we extend our heuristic in [12], so that the minimization of the number of register cells is done in conjunction with a quantity that naturally reflects the difficulty of deriving an appropriate primitive polynomial of degree d. Experimentation shows that the proposed heuristic results again in an overall smaller number of register cells than a partition based approach and in an efficient framework for test pattern generation. } } @TechReport{Dartmouth:PCS-TR91-161, author = {Dimitrios Kagaris and Fillia Makedon }, title = {{On Minimizing Hardware Overhead for Exhaustive Circuit Testability}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-161}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/61/TR91-161.pdf}, abstract = { Exhaustive built-in self testing is given much attention as a viable technique in the context of VLSI technology. In this paper, we present heuristic in order to make exhaustive testing of combinational circuits practical. The goal is to place a small number of register cells on the nets of the input circuit so that the input dependency of combinational elements in the circuit is less than a small given integer k. Our heuristic guarantees that each output can be individually tested with 2k test patterns and can be used as a subroutine to generat efficient test patterns to test all the outputs of the circuit simultaneously. For example, we can connect the register cells in a Linear Feedback Shift Register(LFSR). Minimizing the number of the inserted register cells reduces the hardware overhead as well as the upper bound on the number of test patterns generated. A heuristic approach has been proposed only for the case when an element in the circuit schematic denotes a boolean gate. An element may, however, also be used to represent a combinatorial circuit model. Our heuristic applies to this case as well. Extensive experimentation indicates that the proposed technique is very efficient. } } @TechReport{Dartmouth:PCS-TR91-160, author = {Donald B. Johnson and Panagiotis Metaxas }, title = {{Connected Components in O(lg3/2|V|) Parallel Time for the CREW PRAM}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-160}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/60/TR91-160.pdf}, abstract = { Computing the connected components of an undirected graph G = (V,E) on |V| = n vertices and |E| = m edges is a fundamental computational problem. The best known parallel algorithm for the CREW PRAM model runs on O(lg2n) time using n2/lg2n processors [CLC82,HCS79]. For the CRCW PRAM model in which concurrent writing is permitted, the best known algorithm runs in O(lg n) time using almost (n+m)/lg n processors [SV82,CV86,AS87]. Unfortunately, simulating this algorithm on the weaker CREW model increases its running time to O(lg2n) [CDR86, KR90,Vis83]. We present here an efficient and simple algorithm that runs in O(lg 3/2n) time using n+m CREW processors. } } @TechReport{Dartmouth:PCS-TR91-159, author = {Donald B. Johnson and Panagiotis Metaxas }, title = {{Optimal Parallel and Sequential Algorithms for the Vertex Updating Problem of a Minimum Spanning Tree}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-159}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/59/TR91-159.pdf}, abstract = { We present a set of rules that can be used to give optimal solutions to the vertex updating problem for a minimum spanning tree: Update a given MST when a new vertex z is introducted, along with weighted edges that connect z with the vertices of the graph. These rules lead to simple parallel algorithms that run in O(lg n) parallel time using n/lg n EREW PRAMs. They can also be used to derive simple linear-time sequential algorithms for the same problem. Furthermore, we show how our solution can be used to solve the multiple vertex updating problem. } } @TechReport{Dartmouth:PCS-TR91-158, author = {Matt Bishop }, title = {{Implementation Notes on bdes(1)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-158}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/58/TR91-158.pdf}, abstract = { This note describes the implementation of bdes, the file encryption program being distributed in the 4.4 release of the Berkeley Software Distribution. It implements all modes of the Data Encryption Standard program. } } @TechReport{Dartmouth:PCS-TR91-156, author = {Matt Bishop }, title = {{An Overview of Computer Viruses in a Research Environment}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-156}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/57/TR91-156.pdf}, abstract = { The threat of attack by computer viruses is in reality a very small part of a much more general threat, specifically attacks aimed at subverting computer security. This paper examines computer viruses as malicious logic in a research and development environment, relates them to various models of security and integrity, and examines current research techniques aimed at controlling the threats viruses in particular, and malicious logic in gerneral, pose to computer systems. Finally, a brief examination of the vulnerabilities of research and development systems that malicious logic and computer viruses may exploit is undertaken. } } @TechReport{Dartmouth:PCS-TR91-154, author = {Matt Bishop }, title = {{A Security Analysis of Version 2 of the Network Time Protocol NTP: A Report to the Privacy and Security Research Group}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-154}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/56/TR91-154.pdf}, abstract = { The Network Time Protocol is being used throughout the Internet to provide an accurate time service. This paper examines the security requirements of such a service, analyzes version 2 of the NTP protocol to determine how well it meets these requirements, and suggests improvements where appropriate. } } @TechReport{Dartmouth:PCS-TR91-150, author = {Matt Bishop }, title = {{Privacy-Enhanced Electronic Mail}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR91-150}, year = {1991}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/55/TR91-150.pdf}, abstract = { (Revision 3). The security of electronic mail sent through the Internet may be described in exactly three words: there is none. The Privacy and Security Research Group has recommended implementing mechanisms designed to provide security enhancements. The first set of mechanisms provides a protocol to provide privacy, integrity, and authentication for electronic mail; the second provides a certificate-based key management infrastructure to support key distribution throughout the internet, to support the first set of mechanisms. This paper describes these mechanisms, as well as the reasons behind their selection and how these mechanisms can be used to provide some measure of securtiy in the exchange of electronic mail. } } @TechReport{Dartmouth:PCS-TR90-158, author = {Donald B. Johnson and Larry Raab }, title = {{Finding Optimal Quorum Assigments for Distributed Databases}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-158}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/54/TR90-158.pdf}, abstract = { Replication has been studied as a method of increasing the availability of a data item in a distributed database subject to component failures and consequent partitioning. The potential for partitioning requires that a protocol be employed which guarantees that any access to a data item is aware of the most recent update to that data item. By minimizing the number of access requests denied due to this constraint, we maximize availability. In the event that all access requests are reads, placing one copy of the data item at each site clearly leads to maximum availability. The other extreme, all access requests are write requests or are treated as such, has been studied extensively in the literature. In this paper we investigate the performance of systems with both read and write requests. We describe a distributed on-line algorithm for determining the optimal parameters, or optimal quorum assignments, for a commonly studied protocol, the quorum consensus protocol[9]. We also show how to incorporate these optimization techniques into a dynamic quorum reassignment protocol. In addition, we demonstrate via simulation both the value of this algorithm and the effect of various read-write rations on availability. This simulation, on 101 sites and up to 5050 links(fully- connected), demonstrates that the techniques described here can greatly increase data availability, and that the best quorum assignments are frequently realized at the extreme values of the quorum parameters. } } @TechReport{Dartmouth:PCS-TR90-157, author = {Donald B. Johnson and Larry Raab }, title = {{A Tight Upper Bound on the Benefits of Replication and Consistency Control Protocols}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-157}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/53/TR90-157.pdf}, abstract = { We present an upper bound on the performance provided by a protocol guaranteeing mutually exclusive access to a replicated resource in a network subject to component failure and subsequent partitioning. The bound is presented in terms of the performance of a single resource in the same network. The bound is tight and is the first such bound known to us. Since mutual exclusion is one of the requirements for maintaining the consistency of a database object, this bound provides an upper limit on the availability provided by any database consistency control protocol, including those employing dynamic data relocation and replication. We show that if a single copy provides availability A for 0 <= A <= 1, then no scheme can achieve availability greater than sqrt(A) in the same network. We show this bound to be the best possible for any network with availability greater than .25. Although, as we proved, the problem of calculating A is #P-complete, we describe a method for approximating the optimal location for a single copy which adjusts dynamically to current network characteristcs. This bound is most useful for high availabilities, which tend to be obtainable with modern networks and their constituent components. } } @TechReport{Dartmouth:PCS-TR90-155, author = {Donald B. Johnson and Larry Raab }, title = {{Effects of Replication on Data Availability}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-155}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/52/TR90-155.pdf}, abstract = { In this paper we examine the effects of replication on the availability of data in a large network. This analysis differs from previous analyses in that it compares the performance of a dynamic consistency control protocol not only to that of other consistency control protocols, but also to the performance of non-replication and to an upper bound on data availability. This analysis also differes in that we gather extensive simulations on large networks subject to partitions at realistically high component reliabilities. We examine the dynamic consistency protocol presented by Jajodia and Mutchler [9, 12] and by Long and Paris[18] along with two proposed enhancements to this protocol[10,11]. We study networks of 101 sites and up to 5050 links (fully-connected) in which all components, although highly reliable, are subject to failure. We demonstrate the importance in this realistic environment of an oft neglected parameter of the system model, the ratio of transaction submissions to component failures. We also show the impact of the number of copies on both the protocol performance and the potential of replicaion as measured by the upper bound. Our simulations show that the majority of current protocol performs optimally for topologies that yield availabilities of at least 65%. On the other hand, the availability provided by non-replicaion is inferior to that of the majority of current protocol by a most 5.9 percentage points for these same topologies. At this point of maximum difference, theprimary copy protocol yields availability 59.1% and the majority of current protocol yields availability 65.0%. We discuss the characteristics of the model limiting the performance of replication. } } @TechReport{Dartmouth:PCS-TR90-153, author = {Matt Bishop }, title = {{Administrator's Guide to the Digital Signature Facility "Rover"}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-153}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/51/TR90-153.pdf}, abstract = { This document describes the installation and maintenance of the rover utility, which provides a digital signature capability for internet messages. } } @TechReport{Dartmouth:PCS-TR90-152, author = {Matt Bishop }, title = {{A Proactive Password Checker}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-152}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/50/TR90-152.pdf}, abstract = { Password selection has long been a difficult issue; traditionally, passwords are either assigned by the computer or chosen by the user. When the computer does the assignments, the passwords are often hard to remember; when the User makes the selection, the passwords are often easy to guess. This paper describes a technique, and a mechanism, to allow users to select passwords which to them are easy to remember but to others would be very difficult to guess. The technique is site, user, and group configurable, and allows rapid changing of constraints impossed upon the passwords. Although experience with this technique has been limited, it appears to have much promise. } } @TechReport{Dartmouth:PCS-TR90-151, author = {Matt Bishop }, title = {{Applying the Take-Grant Protection Model}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-151}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/49/TR90-151.pdf}, abstract = { The Take-Grant Protection Model has in the past been used to model multilevel security hierarchies and simple protection systems. The models are extended to include theft of rights and sharing of information, and additional security policies are examined. The analysis suggests that in some cases the basic rules of the Take-Grant Protection Model should be augmented to represent the policy properly; when appropriate, such modifications are made and their effects with respect to the policy and its Take-Grant representations are discussed } } @TechReport{Dartmouth:PCS-TR90-149, author = {L. Paul Chew }, title = {{Term Reduction Using Directed Congruence Closure}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-149}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/48/TR90-149.pdf}, abstract = { Many problems in computer science can be described in terms of reduction rules that tell how to transform terms. Problems that can be handled in this way include interpreting programs, implementing abstract data types, and proving certain kinds of theorems. A terms is said to have a normal form if it can be transformed, using the reduction rules, into a term to which no further reduction rules apply. In this paper, we extend the Congruence Closure Algorithm, an algorithm for finding the consequences of a finite set of equations, to develop Directed Congruence Closure, a technique for finding the normal form of a term provided the reduction rules satisfy the conditions for a regular term rewriting system. This technique is particularly efficient because it inherits, from the Congruence Closure Algorithm, the ability to remember all objects that have already been proved equivalent. } } @TechReport{Dartmouth:PCS-TR90-148, author = {L. Paul Chew }, title = {{There is a Planar Graph Almost as Good as the Complete Graph}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-148}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/47/TR90-148.pdf}, abstract = { Given a set S of points in the plane, there is a triangulation of S such that a path found within this triangulation has length bounded by a constant times the straight-line distance between the endpoints of the path. Specifically, for any two points a and b of S there is a path along edges of the triangulation with length less that 10 times [ab], where [ab] is the straight-line Euclidean distance between a and b. The triangulation that has this property is the L1 metric Delauney triangulation for the set S. This result can be applied to motion planning in the plane. Given a source, a destination, and a set of polygonal obstacles of size n, an O(n) size data structure can be used to find a reasonable approximation to the shortest path between the source and the destination in O (n log n) time. } } @TechReport{Dartmouth:PCS-TR90-147, author = {L. Paul Chew }, title = {{Building Voronoi Diagrams for Convex Polygons in Linear Expected Time}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-147}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/46/TR90-147.pdf}, abstract = { Let P be a list of points in the plane such that the points of P taken in order form the vertices of a convex polygon. We introduce a simple, linear expected-time algorithm for finding the Voronoi diagram of the points in P. Unlike previous results on expected-time algorithms for Voronoi diagrams, this method does not require any assumptions about the distribution of points. With minor modifications, this method can be used to design fast algorithms for certain problems involving unrestricted sets of points. For example, fast expected-time algorithms can be designed to delete a point from a Voronoi diagram, to build an order k Voronoi diagram for an arbitrary set of points, and to determine the smallest enclosing circle for points at the vertices of a convex hull. } } @TechReport{Dartmouth:PCS-TR90-146, author = {L. Paul Chew }, title = {{Planar Graphs and Sparse Graphs from Efficient Motion Planning in the Plane}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-146}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/45/TR90-146.pdf}, abstract = { Given a source, a destination, and a number of obstacles in the plane, the Motion Planning Program is to determine the best path to move an object (a robot) from the source to the destination without colliding with any of the obstacles. For us, motion is restricted to the plane, the robot is represented by a point, and the obstacles are represented by a set of polygons with a total of n vertices among all the polygonal obstacles. } } @TechReport{Dartmouth:PCS-TR90-145, author = {Michael Goldweber and Donald B. Johnson }, title = {{A Bound of Data Availability when Networks Partition}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-145}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/44/TR90-145.pdf}, abstract = { Many consistency or replication control schemes that increase data availability in distributed systems exist, and the search for improvements continues, though there have been no good nontrivial upper bound demonstrating how much improvement is possible. We present a new upper bound for data availability under replication for general networks. In addition we also describe a new technique that yields near optimal levels of data availability with respect to this bound. } } @TechReport{Dartmouth:PCS-TR90-143, author = {Samuel W. Bent }, title = {{Matching Multiple Patterns From Right to Left}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR90-143}, year = {1990}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/43/TR90-143.pdf}, abstract = { We address the problem of matching multiple pattern strings against a text string. Just as the Aho-Corasick algorithm generalizes the Knuth-Morris-Pratt single-pattern algorithm to handle multiple patterns, we exhibit two generalizations of the Boyer-Moore algorithm to handle multiple patterns. In order to obtain worst-case time bounds better than quadratic, our algorithms remember some of the previous history of the matching. } } @TechReport{Dartmouth:PCS-TR89-142, author = {Michael Goldweber and Donald B. Johnson and Larry Raab }, title = {{A Comparison of Consistency Control Protocols}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR89-142}, year = {1989}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/42/TR89-142.pdf}, abstract = { In this paper we analyze three protocols for maintaining the mutual consistency of replicated objects in a distributed computing environment and compare their performance with that of an oracle protocol whose performance is optimal. We examine these protocols, two dynamic protocols and the majority consensus protocol, via simulations using two measures of availability. The analysis shows that the dynamic protocols, under realistic assumptions, do not perform significantly better than the static voting scheme. Finally we demonstrate that none of these approaches perform as well as our oracle protocol which is shown to be an upper bound on availability. } } @TechReport{Dartmouth:PCS-TR89-141, author = {James R. Driscoll and Dennis M. Healy }, title = {{Asymptotically Fast Algorithms for Spherical and Related Transforms}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR89-141}, year = {1989}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/41/TR89-141.pdf}, abstract = { This paper considers the problem of computing the harmonic expansion of functions defined on the sphere. We begin by proving convolution theorems that relate the convolution of two functions on the sphere to a "multiplication" in the sprectral domain, as well as the multiplication of two functions on the sphere to a "convolution" in the spectral domain. These convolution theorems are then used to develop a sampling theorem on the sphere. } } @TechReport{Dartmouth:PCS-TR89-140, author = {Jeffrey Shallit }, title = {{On the Worst Case of Three Algorithms for Computing the Jacobi Symbol}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR89-140}, year = {1989}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/40/TR89-140.pdf}, abstract = { We study the worst-case behavior of three iterative algorithms- Eisenstein's algorithm, Lebesgue's algorithm, and the "ordinary" Jacobi symbol algorithm - for computing the Jacobi symbol. Each algorithm is similar in format to the Euclidean algorithm for computing gcd (u,v). } } @TechReport{Dartmouth:PCS-TR88-139, author = {Peter A. Sandon }, title = {{Learning Object-Centered Representations}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR88-139}, year = {1988}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/39/TR88-139.pdf}, abstract = { When we look at a familiar object from a novel viewpoint, we are usually able to recognize it. In this thesis, we address the problem of learning to recognize objects under transformations associated with viewpoint. Our vision model combines a hierarchical representation of shape features with an explicit representation of the transformation. Shape features are represented in a layered pyramid-shaped subnetwork, while the transformation is explicitly represented in an auxiliary subnetwork. The two connectionist networks are conjunctively combined to allow object- centered shape features to be computed in the upper layers of the network. A simulation of a 2-D translation subnetwork demonstrates the ability to learn to recognize shapes in different locations in an image, such that those same shapes can be recognized in novel locations. Two new learning methods are presented, which provide improved behavior over previous backpropagation methods. Both methods involve ciompetitive interactions among clusters of nodes. The new learning methods demonstrate improved learning over the generalized delta rule when applied to a number of network tasks. In the first method, called error modification, competition is based on the error signals computed from the gradient of the output error. The result of this competition is a set of midified error signals representing a contrast enhanced version of the original errors. The error modification method reduces the occurrence of network configurations that correspond to local error minima. In the second method, called error augmentation, competition is based on that activations of the nodes in the cluster. Network changes resulting from this competition augment those specified by the error gradient computation. This competition is implemented by the trace comparison rule, a new self-organizing mechanism that is effective in developing highly discriminating features within the cluster. The error augmentation method improves learning in the lower network layers when backpropagged error is weak. } } @TechReport{Dartmouth:PCS-TR88-138, author = {Matt Bishop }, title = {{An Application of a Fast Data Encryption Standard Implementation}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR88-138}, year = {1988}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/38/TR88-138.pdf}, abstract = { The Data Encryption Standard is used as the basis for the UNIX password encryption scheme. Some of the security of that scheme depends on the speed of the implementation. This paper presents a mathematical formulation of a fast implementation of the DES in software, discusses how the mathematics can be translated into code, and then analyzes the UNIX password scheme to show how these results can be used to implement it. Experimental results are provided for several computers to show that the given method speeds up the computation of a password by roughly 20 times (depending on the specific computer). } } @TechReport{Dartmouth:PCS-TR88-137, author = {Matt Bishop }, title = {{Theft of Information in the Take-Grant Protection Model}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR88-137}, year = {1988}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/37/TR88-137.pdf}, abstract = { (Revised 5/90). Questions of information flow are in many ways more important than questions of access control, because the goal of many security policies is to thwart the unauthorized release of information, not merely the illicit obtaining of access rights to that information. The Take-Grant Protection Model is an excellent theoretical tool for examining such issues because conditions necessary and sufficienct for information to flow between tow objects, and for rights to object to be obtained or stolen, are known. In this paper we extend these results by examinig the question of information flow from an object the owner of which is unwilling to release that information. Necessary and sufficient conditions for such "theft of information" to occur are derived, and bounds on the number of subjects that must take action for the theft to occur are presented. To emphasize the usefulness of these results, the security policies of complete isolation,transfer of rights with the cooperation of an owner, and transfer of information (but not rights) with the cooperation of the owner are presented; the last is usedto model a simple reference monitor guarding a resource. } } @TechReport{Dartmouth:PCS-TR88-136, author = {Matt Bishop }, title = {{The Sharing of Rights and Information in a Capability-Based Protection System}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR88-136}, year = {1988}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/36/TR88-136.pdf}, abstract = { The paper examines the question of sharing of rights and information in the Take-Grant Protection Model by concentrating on the similarities between the two; in order to do this, we state and prove new theorems for each that specifically show the similarities. The proof for one of the original theorems is also provided. These statements of necessary and sufficient conditions are contrasted to illustrate the proposition that transferring rights and transferring information are fundamentally the same, as one would expect in a capability-based system. We then discuss directions for future research in light of these results. } } @TechReport{Dartmouth:PCS-TR87-139, author = {Peter A. Sandon }, title = {{Learning Object-Centered Representations}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR87-139}, year = {1987}, month = {January}, comment = { This TR number is incorrect. Please see TR88-139. } } @TechReport{Dartmouth:PCS-TR86-135, author = {John R. Meier }, title = {{Making Mail Friendlier: Adding Macintosh features and multimedia documents in UNIX mail}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-135}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/34/TR86-135.pdf}, abstract = { This paper describes a Macintosh application which acts as a front-end to Unix mail. Features of the Macintosh interface such as icons, menus, and windows replace the command driven interface. Complicated editing commands are replaced with mouse selection and cut, copy, and paste. Message can be composed of text, pictures, and any Macintosh file, because they are encoded into plain text, sent through the mail system,and then unencoded by the receiving end. The designs of the mail server and communications interface are such that mail servers and communications other than Unix mail and a serial line may be easily implemented. } } @TechReport{Dartmouth:PCS-TR86-134, author = {Mark Sherman and Robert L. Scot Drysdale }, title = {{Producing Software Using Tools in a Workstation Environment}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-134}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/33/TR86-134.pdf}, abstract = { We discuss how we taught students to build and use translation, interpretive, editing and monitoring tools in an undergraduate software engineering course. Students used the tools on low-cost workstations (Macintoshes) to build large, group projects. The students' projects used all available features of workstation environments, including graphics, windows, fonts, mice, networks, and sound generators. We found that 1) the use of tools increased student productivity, 2) a shift in a data structure and algorithm topics is needed to cover material relevant for workstation environments, 3) new topics in system design are required for a workstation environment, 4) traditional material can be easily illustrated with a workstation environment and 5) students enjoyed being able to manipulate the advanced features of workstations in their work, which in turn increased their motivation for and concentration on the course material. } } @TechReport{Dartmouth:PCS-TR86-132, author = {L. Paul Chew and Robert L. Scot Drysdale }, title = {{Voronoi Diagrams Based on Convex Distance Functions}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-132}, year = {1986}, month = {January}, abstract = { We present an "expanding waves" view of Voronoi diagrams that allows such diagrams to be defined for very general metrics and for distance measures that do not qualify as matrics. If a pebble is dropped into a still pond, circular waves move out from the point of impact. If n pebbles are dropped simultaneously, the paces where wave fronts meet define the Voronoi diagram on the n points of impact. The Voronoi diagram for any normed matric, including the Lp metrics, can be obtained by changing the shape of the wave front from a circle to the shape of the "circle" in that metric. (For example, the "circle" in the L1 metric is diamond shaped.) For any convex wave shape there is a corresponding convex distance function. Even if the shape is not symmetric about its center (a triangle, for example), although the resulting distance function is not a metric, it can still be used to define a Voronoi diagram. Like Voronoi diagrams based on the Euclidean metric, the Voronoi diagrams based on other nomed metrics can be used to solve various closest-point problems (all-nearest-neighbors, minimum spanning trees, etc.). Some of these problems also make sense for convex distance functions which are not metrics. In particular, the "largest empty circle" problem becomes the "largest empty convex shape" problem, and "motion planning for a disc" becomes "motion planning for a convex shape". These problems can both be solved quickly given the Voronoi diagram. We present an asymptotically optimal algorithm for computing Voronoi diagrams based on convex distance functions. } comment = { This TR appears to have been lost. (April 2008) } } @TechReport{Dartmouth:PCS-TR86-131, author = {David B. Levine }, title = {{The Pairwise Intersection Problem for Monotone Polygons}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-131}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/31/TR86-131.pdf}, abstract = { Geometric intersection problems arise in a number of areas of computer science including graphics and VLSI design rule checking. Previous work has concentrated on solving the pairwise intersection problem for line segments and iso-oriented rectangles. This thesis extends that work by presenting efficient algorithms to solve the pairwise intersection problem for monotone polygons. For general segments, the problem has been solved in O(N+I)*logN) time using a sweeping line technique, where N is the number of segments and I is the number of intersections reported. We combine this technique with approaches taken to solve the iso-oriented rectangle problem to yield an algorithm which solves the pairwise intersection problem for monotone polygons in the same asymptotic time. In addition, there are certain classes of line segments for which the pairwise intersection problem may be solved in O(N*logN + I) time, the best possible. We generalize each such class of line segments to a class of polygons and present algorithms to solve the associated polygon problem. Finally, we discuss the impacts which possible improvements to the line segment problem would have on our results. } } @TechReport{Dartmouth:PCS-TR86-130, author = {L. Paul Chew and Robert L. Scot Drysdale }, title = {{Finding Largest Empty Circles with Location Constraints}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-130}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/30/TR86-130.pdf}, abstract = { Let S be a set of n points in the plane and let CH(S) represent the convex hull of S. The Largest Empty Circle (LEC) problem is the problem of finding the largest circle centered with CH(S) such that no point of S lies within the circle. Shamos and Hoey (SH75) outlined an algorithm for solving this problem in time O(n log n) by first computing the Voronoi diagram, V(S), in time O(n log n), then using V(S) and CH(S) to compute the largest empty circle in time O(n). In a recent paper [Tou83], Toussaint pointed out some problems with the algorithm as outlined by Shamos and presented an algorithm which, given V(S) and CH(S), solves the LEC problem in time O(n log n). In this note we show that Shamos' original claim was correct: given V(S) and CH(S), the LEC problem can be solved in time O(n). More generally, given V(S) and a convex k-gon P, the LEC centered within P can be found in time O(k+n). We also improve on an algorithm given by Toussaint for computing the LEC when the center is constrained to lie within an arbitrary simple polygon. Given a set S of n points and an arbitrary simple k-gon P, the largest empty circle centered within P can be found in time O(kn + n log n). This becomes O(kn) if the Voronoi diagram of S is already given. } } @TechReport{Dartmouth:PCS-TR86-129, author = {Ann Marks }, title = {{An Algorithm for Resource Allocation Requiring Low Overhead Communication}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-129}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/29/TR86-129.pdf}, abstract = { A heuristic algorithm for allocating resource units to sites in a distributed system is presented. Starting with a given allocation of sites, the algorithm performs a series of optimizations involving pairs of sites in an attempt to improve the worst pair-wise imbalance present in the system; termination occurs when no further improvement is possible. After outlining the general form of the algorithm, which effectively defines an entire family of algorithms, we present theoretical results that speak to the performance of the algorithm as measured in the number of optimizations that can be done, the amount of control communication required and the worst case imbalance of the resulting allocation. Subsequently, two particular algorithms in the family are given and the results of a simulation study of their performance is presented. } } @TechReport{Dartmouth:PCS-TR86-128, author = {William J. Murray }, title = {{An Image Processing Software Package for the Laser Scanning Phase Modulation Microscope}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-128}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/28/TR86-128.pdf}, abstract = { This thesis documents the most recent effort to develop a user-friendly image processing software package for the Laser Scanning Phase Modulation Microscope (LSPMM). The LSPMM is composed of three integrated subsystems, the Laser Scanning (LS) system, the Phase Modulation (PM) system, and Digital Image Acquisition (DIA) system. Under the control of the image processing software, the DIA system can receive and store the digital image data, display the image on a monochrome monitor, and process the image to provide the microscopist with quantitative information regarding the image. The implementation of this image processing software package required the specification of a four level software hierarchy to serve as an organizational framework, with the highest level interacting with the LSPM microscopist, and the lowest level performing hardware control. This framework should prove useful for the development and implementation of additional software in the future. The programs that were developed accept command line arguments; however, most will interactively query the user if the command line arguments are not known. This software provides the microscopist with the capability to scan, save, and display a 512 by 512 pixel image. The image may be scanned to, saved from, or displayed in either of the two DeAnza image display memory planes. Considerable effort has been made to incorporate all of the devices useful for image processing into a single operating system kernel. This alleviates the problem of taking down one operating system and bringing up another version in order to dump image files on magnetic tape. } } @TechReport{Dartmouth:DCS-TR86-127, author = {John Glenn }, title = {{Binary Trees (v. 2.1 -- September 25, 1985)}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-127}, year = {1986}, month = {January}, abstract = { Binary Tree is a program that uses animation to illustrate insertion, deletion and searching of nodes in a binary search tree. Pre-order, in-order, and post-order tree walks are supported. Binary Tree can also perform a recursive descent parse of arithmetic expressions and show the resulting abstract syntax tree. Lisa Pascal source and application available on a single-sided, MFS format microdisk. } comment = { You may download this disk as a Zip archive. } } @TechReport{Dartmouth:PCS-TR86-126, author = {Mark Sherman and Ann Marks }, title = {{Using Low-Cost Workstations to Investigate Computer Networks and Distributed Systems}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-126}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/26/TR86-126.pdf}, abstract = { A quality education in contemporary computer science requires that students gain experience with realistic systems. Many efforts at bringing empirical computer science to undergraduates focus on rather old technologies, for example, building a compiler or simulating a disk scheduler. Although efforts are being made to use some newer technologies, the efforts are concentrating on teaching traditional material in a new medium. However, the medium itself -- networked workstations in a server environment -- is worthy of exploration by undergraduate students in a laboratory setting. At Dartmouth, we developed a Computer Network Laboratory to let students experiment with computer networks, protocols and distributed systems. Through this article, we wish to share our experiences in the design of the laboratory and give an example of how the laboratory was used in a computer network course. } } @TechReport{Dartmouth:PCS-TR86-125, author = {Mark Sherman and Andy Hisgen and Jonathan Rosenberg and David Alex Lamb }, title = {{Functions Returning Values of Dynamic Size}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-125}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/25/TR86-125.pdf}, abstract = { Modern programming languages, such as Ada (Ichbiah 80), permit the definition of functions that return values whose size can not be determined until the function returns. This paper discusses five implementation techniques that can be used to implement this capability. Comparisons of the techniques are provided and guidelines for selecting a particular technique for a compiler are given. } } @TechReport{Dartmouth:PCS-TR86-124, author = {Mark Sherman }, title = {{A Network Package for the Macintosh Using the DoD Internet Protocols}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-124}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/24/TR86-124.pdf}, abstract = { This memo describes the design, implementation and use of the MacIP libraries and programs for running DoD Internet Protocols on the Macintosh over Apple Talk. It is preliminary documentation and out of date, but it is all that exists. } } @TechReport{Dartmouth:PCS-TR86-123, author = {Keith Vetter and Christopher Roche }, title = {{BRUCE: A Graphics System with Hidden Line and Hidden Surface Algorithms}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-123}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/23/TR86-123.pdf}, abstract = { Accurately representing the physical world by computer is a topic which has direct benefits to fields like chemistry and architecture, and is a source of much research in computer science. This paper examines the steps necessary to develop and implement a graphical system that will allow for the modeling of physical world objects. In particular, this is a description of BRUCE: a graphical system that will describe a world of three dimensional polyhedra, implementing algorithms for hidden line and hidden surface removal. This paper also deals with the problems incurred along the way and suggestions for further improvement of BRUCE. } } @TechReport{Dartmouth:DCS-TR86-122, author = {David Cohn and Stephen Madancy }, title = {{Havoc V.85 Software}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-122}, year = {1986}, month = {January}, abstract = { This disk contains alpha release 85 of the HAVOC system, with examples. It is written in C and 68000 assembler. } comment = { You may download this disk as a Zip archive. } } @TechReport{Dartmouth:PCS-TR86-121, author = {David Cohn and Stephen Madancy }, title = {{Creating Havoc: Havoc Development Program}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-121}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/21/TR86-121.pdf}, abstract = { One area where use of the computer is essential is in the modern scientific laboratory. High speed computation, data storage and data analysis enable scientists to perform experiments that would otherwise be impractical. A problem inherent to the effective use of special purpose laboratory computers, however, is the fact that this equipment has generally been developed for highly specific uses, and has either tried to cope with existing high-level languages or has abandoned the attempt and required the user to program in a low-level assembly or machine language. Our idea was to design, develop and implement a programming language that is suited to the needs of a laboratory scientist. Our results have led us to believe that the best way to achieve our goals was using an interpretive/compiled programming environment (similar in spirit to FORTH) in which large programs could be built in small, coherent pieces, that could easily be tested on as high or low a level as the programmer desired. Our language, Havoc, adheres to these principles while providing many of the more widespread and useful language features not found in FORTH. Besides giving it motivation, this preliminary report describes the current design and implementation status of the HAVOC system. The current version of the HAVOC system is available for the Macintosh. } } @TechReport{Dartmouth:PCS-TR86-120, author = {Ann Kratzer }, title = {{View 3: A Programming Environment for Distributed Programming}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-120}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/20/TR86-120.pdf}, abstract = { View 3 is an experimental programming environment to support the development and use of distributed programs. It builds upon three major concepts. First, distributed programs and distributed processes are basic objects. Second, the port mechanism allows a process to exchange information with another process, a file or an I/O device without concern for the type of the object on the other end of the port. Third, test and use of distributed programs are facilitated by the user interface program screen format that allows the user to control both the format and contents of the physical terminal. } } @TechReport{Dartmouth:PCS-TR86-119, author = {Ann Kratzer }, title = {{Task Queues: A General Model for the Implementation of Communications Protocols}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-119}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/19/TR86-119.pdf}, abstract = { When any computer communications network is built, its communications protocol must always be implemented. The protocol is implementetd on the switching nodes of the network. The node software must respond in real time to events generated external to the switching node. Thus, the software running on a switching node constitutes a concurrent program; this complicates the design, implementation and testing of the switching node software. The task queue model presented in this paper defines a structure for this software that facilitates the design, implementation and testing of communications protocols. } } @TechReport{Dartmouth:PCS-TR86-118, author = {Ann Kratzer }, title = {{A Distributed Strategy for Resource Allocation}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-118}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/18/TR86-118.pdf}, abstract = { In this paper, we present a decentralized algorithm for determining how resources should be allocated to sites. This algorithm is general in the sense that it can be used for allocating different kinds of resources. This algorithm can be applied either statically, used on a quiescent system, or used dynamically as the system runs. Throughout, we consider only systems in which a resource has a fixed cost associated with it regardless of where it may be located (i.e. the system is homogeneous). } } @TechReport{Dartmouth:PCS-TR86-117, author = {Ann Kratzer and Mark Sherman }, title = {{View-3 and Ada: Tools for Building Systems with Many Tasks}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-117}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/17/TR86-117.pdf}, abstract = { This paper discusses some useful features for tools that are intended to be used for developing systems with multiple tasks. We include a description of one tool that has been built, View-3. We also describe some problems that might be encountered when trying to fit this kind of tool into an APSE system. } } @TechReport{Dartmouth:PCS-TR86-116, author = {Mark Sherman and Ann Marks and Rob Collins and Heather Anderson and Jerry Godes and Denis Devlin and Leonid Spector and Vivian Sewelson }, title = {{A Practical, Distributed Environment for Macintosh Software Development}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-116}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/16/TR86-116.pdf}, abstract = { We describe a development environment we created for prototyping software for the Macintosh. The programs are developed and executed on a large time-shared computer but can use the full facilities of the Macintosh. By using this system, we combine the advantages of the large system, such as large amounts of disk storage and automatic file backups, with the advantages of the Macintosh, such as advanced graphics, mouse control and sound synthesis. We also describe several projects that used the distributed development system. We conclude with a description of our future plans for this environment. } } @TechReport{Dartmouth:DCS-TR86-115, author = {Ed Grosz }, title = {{KD Tree Simulator}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-115}, year = {1986}, month = {January}, abstract = { This MFS formatted disk contains an animation program for illustrating KD-Trees (D-dimensional search trees) (actually, only 2 dimensions are shown). Both the runnable application and the Lisa Object Pascal/MacApp sources are included. } comment = { This diskette appears to have been lost (April 2008). } } @TechReport{Dartmouth:DCS-TR86-114, author = {Ed Grosz }, title = {{Music Editor}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-114}, year = {1986}, month = {January}, abstract = { This disk contains a simple music editor that creates resources that can be used directly by the Macintosh Sound Driver. The MFS formatted disk contains both the runnable program and the Lisa Object Pascal/MacApp Sources. } comment = { You may download this disk as a Zip archive. } } @TechReport{Dartmouth:DCS-TR86-113, author = {Joe Bergin and Robert L. Scot Drysdale and Jerry Keough and Larry Gallagher and Vivian Sewelson and Mark Sherman }, title = {{A Collection of MDS Example Programs}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-113}, year = {1986}, month = {January}, abstract = { This MFS formatted disk contains a collection of example programs written for teaching machine architecture concepts using the Macintosh Development System. Sample programs illustrate how instructions can be treated as data, computer arithmetic, looping features, interrupt handling, coroutines, recursive subprograms and stack frames, traps and direct manipulation of the screen. In addition, a supervisor program is provided that implements basic, line-oriented input and output facilities for the 68000 assembly language programs on the Macintosh. } comment = { You may download this disk as a Zip archive. } } @TechReport{Dartmouth:TCS-TR86-112, author = {Mark Sherman and Ann Marks }, title = {{QDT (Quickdraw Terminal) Libraries}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {TCS-TR86-112}, year = {1986}, month = {January}, abstract = { This Unix tar-tape contains the C libraries used on Unix and the PL/1 Libraries used on DCTS for communicating with QDT. (No longer available.) } } @TechReport{Dartmouth:DCS-TR86-111, author = {Mark Sherman }, title = {{QDT (Quickdraw Terminal) Disks}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-111}, year = {1986}, month = {January}, abstract = { This disk set consists of one disk containing a running version of QDT over a serial line, one disk containing a running version of QDT over Apple Talk (using KSP), and one disk containing the Lisa Pascal sources for creating QDT (either version). } comment = { You may download this disk as a Zip archive. } } @TechReport{Dartmouth:DCS-TR86-110, author = {Mark Sherman }, title = {{Stack Package Implementing Tasks and Coroutines for TML Pascal on the Macintosh}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-110}, year = {1986}, month = {January}, abstract = { This disk contains the necessary TML Pascal and MDS Assembler files for implementing tasking and coroutines in TML Pascal Programs. Two example programs and brief documentation are provided. MDS format disk. } comment = { You may download this disk as a Zip archive. } } @TechReport{Dartmouth:DCS-TR86-109, author = {Mark Sherman and Tim Maroney }, title = {{MacIP Sources and Applications}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-109}, year = {1986}, month = {January}, abstract = { The MacIP set consists of three disks, all single-sided, MFS formatted. Two disks contain the Lisa Pascal/Lisa Assembler sources for the network libraries and application programs; the third disk contains the runnable applications along with an AppleTalk configured system. The current version by Tim Maroney fixes all reported bugs mentioned in the MacIP Technical Report and includes the TCP library and Telnet program. } comment = { You may download this disk as a Zip archive. } } @TechReport{Dartmouth:PCS-TR86-108, author = {Joon Sup Lee }, title = {{Dartmouth-Smalltalk: An Exercise in Implementation}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-108}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/8/TR86-108.pdf}, abstract = { This report discusses a preliminary implementation of the Smalltalk-80 virtual machine for Vax/Unix. } } @TechReport{Dartmouth:PCS-TR86-107, author = {Kenneth P. Bogart }, title = {{What Should a Discrete Mathematics Course Be?}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-107}, year = {1986}, month = {January}, abstract = { This paper presents the results of a survey of mathematics and computer science departments on their needs and intentions for survey courses in discrete mathematics. The paper then presents an idealized syllabus for such a course, recognizing that many topics in the syllabus should be regarded as optional. The paper concludes with a brief summary of the experience at Dartmouth in teaching such a course. } comment = { This TR appears to have been lost. (April 2008) } } @TechReport{Dartmouth:PCS-TR86-106, author = {Shinji Nakamura }, title = {{Algorithms for Iterative Array Multiplication}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-106}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/6/TR86-106.pdf}, abstract = { Algorithms for the parallel multiplication of two n bit binary numbers by an iterative array of logic cells are discussed. The regular interconnection structures of the multiplier array cell elements, which are ideal for VLSI implementation, are described. The speed and hardware complexity of two new iterative array algorithms, both of which require n cell delays for one n by n bit multiplication, are compared with a straight-forward iterative array algorithm having a 2n cell delay and its higher radix version having an n cell delay. } } @TechReport{Dartmouth:PCS-TR86-105, author = {Shinji Nakamura }, title = {{Parallel Accessible Memory}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-105}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/5/TR86-105.pdf}, abstract = { A new design of a memory device which allows simultaneous access to more than one location is proposed. The unique feature of this multiple accessibility of the memory is realized by applying a binomial concentrator, a type of sparse crossbar interconnection network, to content-addressable memory. The organization of the memory system and the concentration network structure as well as the network characteristics are described along with a distributive control algorithm. Applications of the memory system to parallel processing environments are also included. } } @TechReport{Dartmouth:PCS-TR86-104, author = {Mark Sherman }, title = {{Uses of Generics in Ada}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-104}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/4/TR86-104.pdf}, abstract = { This paper discusses how Ada generic procedures and packages can be used in novel ways to provide general initialization of records, expressions using discriminants, record field hiding and explicit control of parameter binding. } } @TechReport{Dartmouth:DCS-TR86-103, author = {John W. Scott }, title = {{Digital Logic Simulator}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-103}, year = {1986}, month = {January}, abstract = { Logic is a Macintosh program that simulates discrete, digital logic circuits. The two disks contain an executable version of the program, MacApp sources and brief documentation (which is also available separately in hardcopy). } comment = { You may download this disk as a Zip archive. } } @TechReport{Dartmouth:PCS-TR86-102, author = {John W. Scott }, title = {{Instructions for Using Logic}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {PCS-TR86-102}, year = {1986}, month = {January}, URL = {http://www.cs.dartmouth.edu/cms_file/SYS_techReport/2/TR86-102.pdf}, abstract = { This document provides instructions on the use of "Logic", a digital logic simulator for the Macintosh written for Dartmouth students in the Machine Architecture and Digital Electronics courses. } } @TechReport{Dartmouth:DCS-TR86-101, author = {Mark Sherman }, title = {{Maze Game for the Macintosh}}, institution = {Dartmouth College, Computer Science, address = {Hanover, NH}, number = {DCS-TR86-101}, year = {1986}, month = {January}, abstract = { Maze is a multiperson game using a broadcast protocol on the Macintosh. This disk contains the sources (in TML Pascal) for a Maze game. } comment = { You may download this disk as a Zip archive. } }