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MPI_Finalize.3.rst

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MPI_Finalize

:ref:`MPI_Finalize` |mdash| Terminates MPI execution environment.

SYNTAX

C Syntax

#include <mpi.h>

int MPI_Finalize()

Fortran Syntax

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

MPI_FINALIZE(IERROR)
    INTEGER IERROR

Fortran 2008 Syntax

USE mpi_f08

MPI_Finalize(ierror)
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

OUTPUT PARAMETER

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

DESCRIPTION

This routine cleans up all MPI states. Once this routine is called, no MPI routine (not even MPI_Init) may be called, except for :ref:`MPI_Get_version`, :ref:`MPI_Initialized`, and :ref:`MPI_Finalized`. Unless there has been a call to :ref:`MPI_Abort`, you must ensure that all pending communications involving a process are complete before the process calls :ref:`MPI_Finalize`. If the call returns, each process may either continue local computations or exit without participating in further communication with other processes. At the moment when the last process calls :ref:`MPI_Finalize`, all pending sends must be matched by a receive, and all pending receives must be matched by a send.

:ref:`MPI_Finalize` is collective over all connected processes. If no processes were spawned, accepted, or connected, then this means it is collective over MPI_COMM_WORLD. Otherwise, it is collective over the union of all processes that have been and continue to be connected.

NOTES

All processes must call this routine before exiting. All processes will still exist but may not make any further MPI calls. :ref:`MPI_Finalize` guarantees that all local actions required by communications the user has completed will, in fact, occur before it returns. However, :ref:`MPI_Finalize` guarantees nothing about pending communications that have not been completed; completion is ensured only by :ref:`MPI_Wait`, :ref:`MPI_Test`, or :ref:`MPI_Request_free` combined with some other verification of completion.

For example, a successful return from a blocking communication operation or from :ref:`MPI_Wait` or :ref:`MPI_Test` means that the communication is completed by the user and the buffer can be reused, but does not guarantee that the local process has no more work to do. Similarly, a successful return from :ref:`MPI_Request_free` with a request handle generated by an :ref:`MPI_Isend` nullifies the handle but does not guarantee that the operation has completed. The :ref:`MPI_Isend` is complete only when a matching receive has completed.

If you would like to cause actions to happen when a process finishes, attach an attribute to MPI_COMM_SELF with a callback function. Then, when :ref:`MPI_Finalize` is called, it will first execute the equivalent of an :ref:`MPI_Comm_free` on MPI_COMM_SELF. This will cause the delete callback function to be executed on all keys associated with MPI_COMM_SELF in an arbitrary order. If no key has been attached to MPI_COMM_SELF, then no callback is invoked. This freeing of MPI_COMM_SELF happens before any other parts of MPI are affected. Calling :ref:`MPI_Finalized` will thus return "false" in any of these callback functions. Once you have done this with MPI_COMM_SELF, the results of :ref:`MPI_Finalize` are not specified.

ERRORS

.. seealso:: :ref:`MPI_Init`