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NAME

       MPI_Gather -  Gathers together values from a group of processes

SYNOPSIS

       #include "mpi.h"
       int MPI_Gather ( void *sendbuf, int sendcnt, MPI_Datatype sendtype,
                       void *recvbuf, int recvcount, MPI_Datatype recvtype,
                       int root, MPI_Comm comm )

INPUT PARAMETERS

       sendbuf
              - starting address of send buffer (choice)
       sendcount
              - number of elements in send buffer (integer)
       sendtype
              - data type of send buffer elements (handle)
       recvcount
              - number of elements for any single receive (integer, significant only at root)
       recvtype
              - data type of recv buffer elements (significant only at root) (handle)
       root   - rank of receiving process (integer)
       comm   - communicator (handle)

OUTPUT PARAMETER

       recvbuf
              - address of receive buffer (choice, significant only at root )

NOTES FOR FORTRAN

       All  MPI  routines  in  Fortran  (except  for MPI_WTIME and MPI_WTICK ) have an additional
       argument ierr at the end of the argument list.  ierr  is  an  integer  and  has  the  same
       meaning  as  the  return  value  of  the  routine  in  C.   In  Fortran,  MPI routines are
       subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value;  C  routines  as
       the  value of the function and Fortran routines in the last argument.  Before the value is
       returned, the current MPI error handler is called.  By default, this error handler  aborts
       the  MPI  job.   The error handler may be changed with MPI_Errhandler_set ; the predefined
       error handler MPI_ERRORS_RETURN may be used to cause error values to  be  returned.   Note
       that MPI does not guarentee that an MPI program can continue past an error.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_COMM
              -  Invalid  communicator.   A  common error is to use a null communicator in a call
              (not even allowed in MPI_Comm_rank ).
       MPI_ERR_COUNT
              - Invalid count argument.  Count arguments must be non-negative; a count of zero is
              often valid.
       MPI_ERR_TYPE
              -   Invalid   datatype   argument.    May   be  an  uncommitted  MPI_Datatype  (see
              MPI_Type_commit ).
       MPI_ERR_BUFFER
              - Invalid buffer pointer.  Usually a null buffer where one is not valid.

LOCATION

       gather.c

                                            11/14/2001                              MPI_Gather(3)