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NAME

       MPI_Op_commute   -    Queries   an  MPI  reduction  operation  for  its
       commutativity.

SYNOPSIS

       int MPI_Op_commutative(MPI_Op op, int *commute)

INPUT PARAMETERS

       op     - operation (handle)

OUTPUT PARAMETERS

       commute
              - Flag is true if op is a commutative operation. (logical)

NULL HANDLES

       The MPI 1.1 specification, in the section on opaque objects, explicitly
       disallows freeing a null communicator.  The text from the standard is:
       A null handle argument is an erroneous IN argument in MPI calls, unless an
       exception is explicitly stated in the text that defines the function. Such
       exception is allowed for handles to request objects in Wait and Test calls
       (sections Communication Completion and Multiple Completions ). Otherwise, a
       null handle can only be passed to a function that allocates a new object and
       returns a reference to it in the handle.

THREAD AND INTERRUPT SAFETY

       This  routine  is  thread-safe.   This  means  that this routine may be
       safely used by multiple threads without the need for any  user-provided
       thread  locks.  However, the routine is not interrupt safe.  Typically,
       this is due to the use of memory allocation routines such as malloc  or
       other  non-MPICH  runtime  routines  that are themselves not interrupt-
       safe.

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_Comm_set_errhandler (for
       communicators),    MPI_File_set_errhandler     (for     files),     and
       MPI_Win_set_errhandler   (for   RMA   windows).    The   MPI-1  routine
       MPI_Errhandler_set  may  be  used  but  its  use  is  deprecated.   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; however, MPI implementations will
       attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_ARG
              - Invalid  argument.   Some  argument  is  invalid  and  is  not
              identified by a specific error class (e.g., MPI_ERR_RANK ).

SEE ALSO

       MPI_Op_create

LOCATION

       /tmp/gyCYfBi4J6/mpich-3.1/src/mpi/coll/op_commutative.c

                                   2/20/2014                 MPI_Op_commute(3)



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