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MPI_Comm_test_inter(3OpenMPI)                                                  MPI_Comm_test_inter(3OpenMPI)



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  possi-ble possible
       ble  for MPI_SIMILAR to result because either the local or remote groups were similar but not identi-cal. identical.
       cal.

       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




Open MPI 1.2                                   September 2006                  MPI_Comm_test_inter(3OpenMPI)