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.. _mpi_comm_test_inter:
MPI_Comm_test_inter
===================
.. include_body
:ref:`MPI_Comm_test_inter` |mdash| Tests to see if a comm is an
intercommunicator.
SYNTAX
------
C Syntax
^^^^^^^^
.. code-block:: c
#include <mpi.h>
int MPI_Comm_test_inter(MPI_Comm comm, int *flag)
Fortran Syntax
^^^^^^^^^^^^^^
.. code-block:: fortran
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_TEST_INTER(COMM, FLAG, IERROR)
INTEGER COMM, IERROR
LOGICAL FLAG
Fortran 2008 Syntax
^^^^^^^^^^^^^^^^^^^
.. code-block:: fortran
USE mpi_f08
MPI_Comm_test_inter(comm, flag, ierror)
TYPE(MPI_Comm), INTENT(IN) :: comm
LOGICAL, INTENT(OUT) :: flag
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
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:
:ref:`MPI_Comm_size`
Returns the size of the local group.
:ref:`MPI_Comm_group`
Returns the local group.
:ref:`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 :ref:`MPI_Comm_remote_group` and
:ref:`MPI_Comm_remote_size` functions.
The operation :ref:`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: :ref:`MPI_Comm_remote_size`, :ref:`MPI_Comm_remote_group`.
The intercommunicator accessors (:ref:`MPI_Comm_test_inter`,
:ref:`MPI_Comm_remote_size`, MPI_Comm_remote_group) are all local operations.
ERRORS
------
.. include:: ./ERRORS.rst
.. seealso::
* :ref:`MPI_Comm_remote_group`
* :ref:`MPI_Comm_remote_size`
* :ref:`MPI_Intercomm_create`
* :ref:`MPI_Intercomm_merge`
|
