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MPI_FINALIZE(3) Open MPI MPI_FINALIZE(3)

MPI_Finalize — 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 MPI_Get_version, MPI_Initialized, and MPI_Finalized. Unless there has been a call to MPI_Abort, you must ensure that all pending communications involving a process are complete before the process calls 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 MPI_Finalize, all pending sends must be matched by a receive, and all pending receives must be matched by a send.

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. MPI_Finalize guarantees that all local actions required by communications the user has completed will, in fact, occur before it returns. However, MPI_Finalize guarantees nothing about pending communications that have not been completed; completion is ensured only by MPI_Wait, MPI_Test, or MPI_Request_free combined with some other verification of completion.

For example, a successful return from a blocking communication operation or from MPI_Wait or 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 MPI_Request_free with a request handle generated by an MPI_Isend nullifies the handle but does not guarantee that the operation has completed. The 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 MPI_Finalize is called, it will first execute the equivalent of an 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 MPI_Finalized will thus return “false” in any of these callback functions. Once you have done this with MPI_COMM_SELF, the results of MPI_Finalize are not specified.

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_Init


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December 2, 2024