1HPL_logsort(3)               HPL Library Functions              HPL_logsort(3)
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NAME

6       HPL_logsort - Sort the processes in logarithmic order.
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SYNOPSIS

9       #include "hpl.h"
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11       void HPL_logsort( const int NPROCS, const int ICURROC, int * IPLEN, int
12       * IPMAP, int * IPMAPM1 );
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DESCRIPTION

15       HPL_logsort computes an array  IPMAP  and  its inverse   IPMAPM1   that
16       contain   the  logarithmic sorted processes id with repect to the local
17       number of rows of  U  that they own. This is necessary to  ensure  that
18       the  logarithmic  spreading of U is optimal in terms of number of steps
19       and communication volume as well.  In other words,  the  larget  pieces
20       of U will be sent a minimal number of times.
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ARGUMENTS

23       NPROCS  (global input)          const int
24               On  entry,  NPROCS  specifies the number of process rows in the
25               process grid. NPROCS is at least one.
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27       ICURROC (global input)          const int
28               On entry, ICURROC is the source process row.
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30       IPLEN   (global input/output)   int *
31               On entry, IPLEN is an array of dimension NPROCS+1,   such  that
32               IPLEN[0]  is  0, and IPLEN[i] contains the number of rows of U,
33               that process i-1 has.  On exit,  IPLEN[i]  is  the  number   of
34               rows  of  U  in the processes before process IPMAP[i] after the
35               sort,  with  the convention that  IPLEN[NPROCS] is   the  total
36               number   of  rows  of the panel.  In other words,  IPLEN[i+1] -
37               IPLEN[i] is  the  number of rows of A that should be  moved  to
38               the  process  IPMAP[i].  IPLEN  is such that the number of rows
39               of  the  source process  row is IPLEN[1] - IPLEN[0],   and  the
40               remaining   entries   of  this  array  are  sorted  so that the
41               quantities IPLEN[i+1]-IPLEN[i] are logarithmically sorted.
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43       IPMAP   (global output)         int *
44               On entry,  IPMAP  is an array of dimension  NPROCS.   On  exit,
45               array  contains   the logarithmic mapping of the processes.  In
46               other words, IPMAP[myroc] is the corresponding  sorted  process
47               coordinate.
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49       IPMAPM1 (global output)         int *
50               On  entry,  IPMAPM1  is an array of dimension NPROCS.  On exit,
51               this  array  contains  the inverse of the  logarithmic  mapping
52               contained   in   IPMAP:  IPMAPM1[ IPMAP[i] ] = i,  for all i in
53               [0.. NPROCS)
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SEE ALSO

56       HPL_plindx1 (3),         HPL_plindx10 (3),          HPL_pdlaswp01N (3),
57       HPL_pdlaswp01T (3).
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61HPL 2.1                        October 26, 2012                 HPL_logsort(3)
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