MPI_OP_CREATE, MPI_Op_create

Purpose

Binds a user-defined reduction operation to an op handle.

C synopsis

#include <mpi.h>
int MPI_Op_create(MPI_User_function *function,int commute,MPI_Op *op);

C++ synopsis

#include mpi.h
void MPI::Op::Init(MPI::User_function *func, bool commute);

FORTRAN synopsis

include 'mpif.h' or use mpi
MPI_OP_CREATE(EXTERNAL FUNCTION,INTEGER COMMUTE,INTEGER OP,INTEGER IERROR)

Parameters

function
     is the user-defined reduction function (function) (IN)

commute
     is true if commutative; otherwise it is false (IN)

op
     is the reduction operation (handle) (OUT)

IERROR
     is the FORTRAN return code. It is always the last argument.

Description

This subroutine binds a user-defined reduction operation to an op handle
which you can then use in MPI_REDUCE, MPI_ALLREDUCE, MPI_REDUCE_SCATTER and
MPI_SCAN and their nonblocking equivalents.

The user-defined operation is assumed to be associative. If commute = true,
then the operation must be both commutative and associative. If commute =
false, then the order of the operation is fixed. The order is defined in
ascending, task rank order and begins with task zero.

function is a user-defined function. It must have the following four
arguments: invec, inoutvec, len, and datatype.

The following is the ANSI-C prototype for the function:

typedef void MPI_User_function(void *invec, void *inoutvec,
    int *len, MPI_Datatype *datatype);

The following is the FORTRAN declaration for the function:

SUBROUTINE USER_FUNCTION(INVEC(*), INOUTVEC(*), LEN, TYPE)
<type> INVEC(LEN), INOUTVEC(LEN)
 INTEGER LEN, TYPE

Notes

See IBM Parallel Environment for AIX: MPI Programming Guide for information
about reduction functions.

Errors

Null function

MPI not initialized

MPI already finalized

Related information

     MPI_ALLREDUCE
     MPI_OP_FREE
     MPI_REDUCE
     MPI_REDUCE_SCATTER