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MPIX_Comm_get_failed

:ref:`MPIX_Comm_get_failed` - Obtain a group that lists failed processes in a communicator.

This is part of the User Level Fault Mitigation :ref:`ULFM extension <ulfm-label>`.

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 :ref:`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

.. seealso::
   * :ref:`MPIX_Comm_revoke`
   * :ref:`MPIX_Comm_ack_failed`