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.TH HPL_logsort 3 "September 10, 2008" "HPL 2.0" "HPL Library Functions"
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.SH NAME
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HPL_logsort \- Sort the processes in logarithmic order.
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.SH SYNOPSIS
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\fB\&#include "hpl.h"\fR
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\fB\&void\fR
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\fB\&HPL_logsort(\fR
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\fB\&const int\fR
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\fI\&NPROCS\fR,
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\fB\&const int\fR
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\fI\&ICURROC\fR,
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\fB\&int *\fR
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\fI\&IPLEN\fR,
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\fB\&int *\fR
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\fI\&IPMAP\fR,
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\fB\&int *\fR
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\fI\&IPMAPM1\fR
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\fB\&);\fR
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.SH DESCRIPTION
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\fB\&HPL_logsort\fR
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computes an array  IPMAP  and  its inverse  IPMAPM1  that
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contain  the logarithmic sorted processes id with repect to the local
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number of rows of  U  that they own. This is necessary to ensure that
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the logarithmic spreading of U is optimal in terms of number of steps
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and communication volume as well.  In other words,  the larget pieces
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of U will be sent a minimal number of times.
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.SH ARGUMENTS
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.TP 8
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NPROCS  (global input)          const int
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On entry, NPROCS  specifies the number of process rows in the
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process grid. NPROCS is at least one.
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.TP 8
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ICURROC (global input)          const int
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On entry, ICURROC is the source process row.
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.TP 8
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IPLEN   (global input/output)   int *
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On entry, IPLEN is an array of dimension NPROCS+1,  such that
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IPLEN[0] is 0, and IPLEN[i] contains the number of rows of U,
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that process i-1 has.  On exit,  IPLEN[i]  is  the number  of
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rows of U  in the processes before process IPMAP[i] after the
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sort,  with  the convention that  IPLEN[NPROCS] is  the total
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number  of rows  of the panel.  In other words,  IPLEN[i+1] -
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IPLEN[i] is  the  number of rows of A that should be moved to
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the process IPMAP[i].  IPLEN  is such that the number of rows
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of  the  source process  row is IPLEN[1] - IPLEN[0],  and the
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remaining  entries  of  this  array  are  sorted  so that the
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quantities IPLEN[i+1]-IPLEN[i] are logarithmically sorted.
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.TP 8
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IPMAP   (global output)         int *
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On entry,  IPMAP  is an array of dimension  NPROCS.  On exit,
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array contains  the logarithmic mapping of the processes.  In
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other words, IPMAP[myroc] is the corresponding sorted process
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coordinate.
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.TP 8
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IPMAPM1 (global output)         int *
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On entry, IPMAPM1  is an array of dimension NPROCS.  On exit,
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this  array  contains  the inverse of the logarithmic mapping
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contained  in  IPMAP:  IPMAPM1[ IPMAP[i] ] = i,  for all i in
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[0.. NPROCS)
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.SH SEE ALSO
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.BR HPL_plindx1 \ (3),
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.BR HPL_plindx10 \ (3),
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.BR HPL_pdlaswp01N \ (3),
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.BR HPL_pdlaswp01T \ (3).