MPI_Comm_compare

MPI_Comm_compare(3)                   MPI                  MPI_Comm_compare(3)



NAME
       MPI_Comm_compare -  Compares two communicators

SYNOPSIS
       int MPI_Comm_compare(MPI_Comm comm1, MPI_Comm comm2, int *result)

INPUT PARAMETERS
       comm1  - comm1 (handle)
       comm2  - comm2 (handle)


OUTPUT PARAMETERS
       result - integer which is MPI_IDENT if the contexts and groups are the
              same, MPI_CONGRUENT if different contexts but identical groups,
              MPI_SIMILAR if different contexts but similar groups, and
              MPI_UNEQUAL otherwise


USING 'MPI_COMM_NULL' WITH 'MPI_COMM_COMPARE'
       It is an error to use MPI_COMM_NULL as one of the arguments to
       MPI_Comm_compare .  The relevant sections of the MPI standard are

       .  (2.4.1 Opaque Objects) 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.

       .  (5.4.1. Communicator Accessors) where there is no text in
       MPI_COMM_COMPARE allowing a null 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.  (To perform the communicator comparisions, this routine may need
       to allocate some memory.  Memory allocation is not interrupt-safe, and
       hence this routine is only thread-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 ).

LOCATION
       src/mpi/comm/comm_compare.c



                                   4/24/2013               MPI_Comm_compare(3)