MPI_Reduce(3)

NAME
     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 (choice)

     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.