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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