BIB-VERSION:: CS-TR-v2.0
ID:: ncstrl.dartmouthcs//TR2003-445
ENTRY:: April 11, 2003
ORGANIZATION:: Dartmouth College, Computer Science
TITLE:: Relaxing the Problem-Size Bound for Out-of-Core Columnsort
TYPE:: Technical Report (paper)
REVISION:: 1
AUTHOR:: Chaudhry, Geeta
AUTHOR:: Hamon, Elizabeth A. 
AUTHOR:: Cormen, Thomas H. 
DATE:: April 2003
RETRIEVAL:: For a paper copy, email <reports@cs.dartmouth.edu>
RETRIEVAL:: For a paper copy, write to
       Technical Report Librarian
       Department of Computer Science
       Dartmouth College
       6211 Sudikoff Laboratory
       Hanover, NH 03755-3510
       USA
RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2003-445.ps.Z
RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/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.
END:: ncstrl.dartmouthcs//TR2003-445