MPI_Comm_compare - Compares two communicators
int MPI_Comm_compare(MPI_Comm comm1, MPI_Comm comm2, int *result)
- - comm1 (handle)
- - comm2 (handle)
- - 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
It is an error to use MPI_COMM_NULL
as one of the arguments to
. 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
allowing a null handle.
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.)
All MPI routines in Fortran (except for MPI_WTIME
have an additional argument ierr
at the end of the argument list.
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
All MPI objects (e.g., MPI_Datatype
) are of type
All MPI routines (except MPI_Wtime
) 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 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
guarentee that an MPI program can continue past an error; however,
MPI implementations will attempt to continue whenever possible.
- - No error; MPI routine completed successfully.
- - Invalid argument. Some argument is invalid and is not identified by a
specific error class (e.g., MPI_ERR_RANK ).