HPL_reduce - Reduce operation.
#include "hpl.h"
int HPL_reduce( void * BUFFER,
const int COUNT, const HPL_T_TYPE DTYPE,
const HPL_T_OP OP, const int ROOT,
MPI_Comm COMM );
HPL_reduce performs a global reduce operation across all processes of a
group. Note that the input buffer is used as workarray and in all processes
but the accumulating process corrupting the original data.
- BUFFER (local input/output) void *
- On entry, BUFFER points to the buffer to be reduced. On exit, and in
process of rank ROOT this array contains the reduced data. This buffer is
also used as workspace during the operation in the other processes of the
group.
- COUNT (global input) const int
- On entry, COUNT indicates the number of entries in BUFFER. COUNT must be
at least zero.
- DTYPE (global input) const HPL_T_TYPE
- On entry, DTYPE specifies the type of the buffers operands.
- OP (global input) const HPL_T_OP
- On entry, OP is a pointer to the local combine function.
- ROOT (global input) const int
- On entry, ROOT is the coordinate of the accumulating process.
- COMM (global/local input) MPI_Comm
- The MPI communicator identifying the process collection.
HPL_broadcast (3), HPL_all_reduce (3),
HPL_barrier (3), HPL_min (3),
HPL_max (3), HPL_sum (3).