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

6       HPL_reduce - Reduce operation.
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SYNOPSIS

9       #include "hpl.h"
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11       int HPL_reduce( void * BUFFER, const int COUNT, const HPL_T_TYPE DTYPE,
12       const HPL_T_OP OP, const int ROOT, MPI_Comm COMM );
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DESCRIPTION

15       HPL_reduce performs a global reduce operation across all processes of a
16       group.   Note  that  the  input buffer is  used as workarray and in all
17       processes but the accumulating process corrupting the original data.
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ARGUMENTS

20       BUFFER  (local input/output)    void *
21               On entry,  BUFFER  points to  the  buffer to be   reduced.   On
22               exit,   and   in process of rank  ROOT  this array contains the
23               reduced data.  This  buffer  is also used as  workspace  during
24               the operation in the other processes of the group.
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26       COUNT   (global input)          const int
27               On  entry,   COUNT  indicates the number of entries in  BUFFER.
28               COUNT must be at least zero.
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30       DTYPE   (global input)          const HPL_T_TYPE
31               On entry,  DTYPE  specifies the type of the buffers operands.
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33       OP      (global input)          const HPL_T_OP
34               On entry, OP is a pointer to the local combine function.
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36       ROOT    (global input)          const int
37               On entry, ROOT is the coordinate of the accumulating process.
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39       COMM    (global/local input)    MPI_Comm
40               The MPI communicator identifying the process collection.
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SEE ALSO

43       HPL_broadcast (3),  HPL_all_reduce (3),  HPL_barrier (3),  HPL_min (3),
44       HPL_max (3), HPL_sum (3).
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48HPL 2.1                        October 26, 2012                  HPL_reduce(3)
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