MPI_Allreduce - Combines values from all processes and
distributes the result back to all processes
SYNOPSIS
C:
#include <mpi.h>
int MPI_Allreduce ( sendbuf, recvbuf, count,
datatype, op, comm )
void *sendbuf;
void *recvbuf;
int count;
MPI_Datatype datatype;
MPI_Op op;
MPI_Comm comm;
C++:
#include <mpi.h>
void Intracomm::Allreduce(
const void* sendbuf,
void* recvbuf,
int count,
const Datatype& datatype,
const Op& op) const
Fortran:
INCLUDE "mpif.h" (or USE MPI)
<type> SENDBUF(*), RECVBUF(*)
INTEGER count, datatype, op,
comm, ierror,
CALL MPI_ALLREDUCE(sendbuf, recvbuf, count,
datatype, op, comm, ierror,)
STANDARDS
This release implements the MPI 1.2 standard, as
documented by the MPI Forum in the spring 1997 release of
MPI: A Message Passing Interface Standard.
DESCRIPTION
The MPI_Allreduce routine combines values from all
processes and distributes the result back to all
processes. This routine accepts the following parameters:
sendbuf Specifies the starting address of the send
count Specifies the number of elements in the send
buffer (integer)
datatype Specifies the data type of elements in the send
buffer (handle)
op Specifies the operation (handle)
comm Specifies the communicator (handle)
recvbuf Returns the starting address of the receive
buffer (choice)
ierror Specifies the return code value for successful
completion, which is in MPI_SUCCESS.
MPI_SUCCESS is defined in the mpif.h file.
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