17.2.46. MPI_Comm_compare

MPI_Comm_compare - Compares two communicators.

17.2.46.1. Syntax

17.2.46.1.1. C Syntax

#include <mpi.h>

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

17.2.46.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_COMM_COMPARE(COMM1, COMM2, RESULT, IERROR)
    INTEGER COMM1, COMM2, RESULT, IERROR

17.2.46.1.3. Fortran 2008 Syntax

USE mpi_f08

MPI_Comm_compare(comm1, comm2, result, ierror)
    TYPE(MPI_Comm), INTENT(IN) :: comm1, comm2
    INTEGER, INTENT(OUT) :: result
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.46.2. Input Parameters

  • comm1 : Comm1 (handle).

  • comm2 : Comm2 (handle).

17.2.46.3. Output Parameters

  • result : Result of comparison (integer).

  • IERROR : Fortran only: Error status (integer).

17.2.46.4. Description

MPI_IDENT results if and only if comm1 and comm2 are handles for the same object (identical groups and same contexts). MPI_CONGRUENT results if the underlying groups are identical in constituents and rank order; these communicators differ only by context. MPI_SIMILAR results of the group members of both communicators are the same but the rank order differs. MPI_UNEQUAL results otherwise.

17.2.46.5. Errors

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.