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.. _mpix_comm_get_failed:
MPIX_Comm_get_failed
====================
.. include_body
: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
^^^^^^^^
.. code-block:: c
#include <mpi.h>
#include <mpi-ext.h>
int MPIX_Comm_get_failed(MPI_Comm comm, MPI_Group *failedgrp)
Fortran Syntax
^^^^^^^^^^^^^^
.. code-block:: fortran
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
^^^^^^^^^^^^^^^^^^^
.. code-block:: fortran
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
------
.. include:: ./ERRORS.rst
.. seealso::
* :ref:`MPIX_Comm_revoke`
* :ref:`MPIX_Comm_ack_failed`
|
