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MPI_Comm_compare(3) MPI MPI_Comm_compare(3)
MPI_Comm_compare - Compares two communicators
int MPI_Comm_compare(MPI_Comm comm1, MPI_Comm comm2, int *result)
comm1 - comm1 (handle)
comm2 - comm2 (handle)
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
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
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.
- 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 ).