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HPL_reduce(3)		      HPL Library Functions		   HPL_reduce(3)

NAME
     HPL_reduce - Reduce operation.

SYNOPSIS
     #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 );

DESCRIPTION
     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.

ARGUMENTS
     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.

SEE ALSO
     HPL_broadcast (3),   HPL_all_reduce (3),	HPL_barrier (3),    HPL_min (3),
     HPL_max (3), HPL_sum (3).

HPL 2.3 			December 2, 2018		   HPL_reduce(3)

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