SYNTAX

   C Syntax
          #include <mpi.h>
          #include <mpi-ext.h>

          int MPIX_Comm_get_failed(MPI_Comm comm, MPI_Group *failedgrp)

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

          MPIX_COMM_GET_FAILED(COMM, FAILEDGRP, IERROR)
               INTEGER COMM, FAILEDGRP, IERROR

   Fortran 2008 Syntax
          USE mpi_f08
          USE mpi_ext_f08

          MPIX_Comm_get_failed(comm, failedgrp, ierror)
               TYPE(MPI_Comm), INTENT(IN) :: comm
               TYPE(MPI_Group), INTENT(OUT) :: failedgrp
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

       • comm: Communicator (handle).

OUTPUT PARAMETERS

       • failedgrp: Group (handle).

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

DESCRIPTION

       This local operation returns the group failedgrp of processes from the communicator comm that are locally
       known to have failed.  The failedgrp can be empty, that is, equal to MPI_GROUP_EMPTY.

       For  any  two groups obtained from calls to that routine at the same MPI process, with the same comm, the
       intersection of the largest group with the smallest group is MPI_IDENT to the smallest  group,  that  is,
       the same processes have the same ranks in the two groups, up to the size of the smallest group.

PROCESS FAILURES

       MPI makes no assumption about asynchronous progress of the failure detection.  A valid MPI implementation
       may  choose to update the group of locally known failed MPI processes only when it enters a function that
       must raise a fault tolerance error.

       It is possible that only the calling MPI process has detected the reported failure. If  global  knowledge
       is  necessary, MPI processes detecting failures should call MPIX_Comm_revoke to enforce an error at other
       ranks.

WHEN COMMUNICATOR IS AN INTER-COMMUNICATOR

       When the communicator is an inter-communicator, the value of failedgrp contains the members known to have
       failed in both the local and the remote groups of comm.

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:

          • MPIX_Comm_revoke

          • MPIX_Comm_ack_failed

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                           MPIX_COMM_GET_FAILED(3)