MPI_Comm_test_inter(3)             Open MPI             MPI_Comm_test_inter(3)



NAME
       MPI_Comm_test_inter  - Tests to see if a comm is an intercommunicator.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Comm_test_inter(MPI_Comm comm, int *flag)


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_COMM_TEST_INTER(COMM, FLAG, IERROR)
            INTEGER   COMM, IERROR
            LOGICAL   FLAG


C++ Syntax
       #include <mpi.h>
       bool Comm::Is_inter() const


INPUT PARAMETER
       comm      Communicator (handle).


OUTPUT PARAMETERS
       flag     (Logical.)

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       This local routine allows the calling process to determine the type of
       a communicator. It returns true for an intercommunicator, false for an
       intracommunicator.

       The type of communicator also affects the value returned by three other
       functions.  When dealing with an intracommunicator (enables
       communication within a single group), the functions listed below return
       the expected values, group size, group, and rank.  When dealing with an
       inter-communicator, however, they return the following values:

       MPI_Comm_size  Returns the size of the local group.
       MPI_Comm_group Returns the local group.
       MPI_Comm_rank  Returns the rank in the local group.

       To return the remote group and remote group size of an inter-
       communicator, use the MPI_Comm_remote_group and MPI_Comm_remote_size
       functions.

       The operation MPI_Comm_compare is valid for intercommunicators. Both
       communicators must be either intra- or intercommunicators, or else
       MPI_UNEQUAL results. Both corresponding local and remote groups must
       compare correctly to get the results MPI_CONGRUENT and MPI_SIMILAR. In
       particular, it is possible for MPI_SIMILAR to result because either the
       local or remote groups were similar but not identical.

       The following accessors provide consistent access to the remote group
       of an intercommunicator: MPI_Comm_remote_size, MPI_Comm_remote_group.

       The intercommunicator accessors (MPI_Comm_test_inter,
       MPI_Comm_remote_size, MPI_Comm_remote_group) are all local operations.


ERRORS
       Almost all MPI routines return an error value; C routines as the value
       of the function and Fortran routines in the last argument. C++
       functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       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.


SEE ALSO
       MPI_Comm_remote_group
       MPI_Comm_remote_size
       MPI_Intercomm_create
       MPI_Intercomm_merge




1.4.1                            Jan 14, 2010           MPI_Comm_test_inter(3)
