MPI_Reduce - Reduces values on all processes to a single
value
SYNOPSIS
C:
#include <mpi.h>
int MPI_Reduce ( sendbuf, recvbuf, count, datatype,
op, root, comm )
void *sendbuf;
void *recvbuf;
int count;
MPI_Datatype datatype;
MPI_Op op;
int root;
MPI_Comm comm;
C++:
#include <mpi.h>
void Intracomm::Reduce(
const void* sendbuf,
void* recvbuf,
int count,
const Datatype& datatype,
const Op& op,
int root) const
Fortran:
INCLUDE "mpif.h" (or USE MPI)
<type> SENDBUF(*), RECVBUF(*)
INTEGER count, datatype, op, root, comm, ierror
CALL MPI_REDUCE(sendbuf, recvbuf, count, datatype, op, root, 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_Reduce routine reduces values on all processes to
a single value. This routine accepts the following
parameters:
sendbuf Specifies the address of the send buffer
count Specifies the number of elements in the send
buffer (integer)
datatype Specifies the data type of elements of the send
buffer (handle)
op Specifies the reduce operation (handle)
root Specifies the rank of the root process (integer)
comm Specifies the communicator (handle)
recvbuf Returns the address of the receive buffer
(choice, significant only at root)
ierror Specifies the return code value for successful
completion, which is in MPI_SUCCESS.
MPI_SUCCESS is defined in the mpif.h file.
NOTES
This implementation currently uses a simple tree
algorithm.
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