plucky (3) MPI_Comm_test_inter.openmpi.3.gz

SYNTAX

   C Syntax
          #include <mpi.h>

          int MPI_Comm_test_inter(MPI_Comm comm, int *flag)

   Fortran Syntax
          USE MPI
          ! or the older form: INCLUDE 'mpif.h'
          MPI_COMM_TEST_INTER(COMM, FLAG, IERROR)
               INTEGER COMM, IERROR
               LOGICAL FLAG

   Fortran 2008 Syntax
          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:

       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 return result of the function and
       Fortran routines in the last argument.

       Before the error value is returned, the current MPI  error  handler  associated  with  the  communication
       object  (e.g.,  communicator, window, file) is called.  If no communication object is associated with the
       MPI call, then the call is considered attached to MPI_COMM_SELF and will call the  associated  MPI  error
       handler.   When   MPI_COMM_SELF   is   not  initialized  (i.e.,  before  MPI_Init/MPI_Init_thread,  after
       MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial  error  handler.
       The  initial  error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using
       the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info  key  to  MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.   If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
       error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is  called  for  all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called on a communicator, it acts as if MPI_Abort was called on  that  communicator.  If  called  on  a
         window  or file, acts as if MPI_Abort was called on a communicator containing the group of processes in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more information.

       SEE ALSO:

          • MPI_Comm_remote_group

          • MPI_Comm_remote_size

          • MPI_Intercomm_create

          • MPI_Intercomm_merge

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                            MPI_COMM_TEST_INTER(3)