MPI_FINALIZE(3)					     Open MPI					   MPI_FINALIZE(3)

MPI_Finalize — Terminates MPI world model.

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 finalizes the MPI world model.  If the MPI world model has been initialized in an MPI process,
       it  must	 be finalized exactly once by invoking this routine during the lifetime of that MPI process.  This
       is different than the MPI session model, which can be initialized and finalized multiple times  in  an  MPI
       process.	 See MPI_Session_init <#mpi-session-init> and MPI_Session_finalize <#mpi-session-finalize>.

       Unless  there has been a call to MPI_Abort <#mpi-abort>, you must ensure that all pending communications in
       the MPI world model 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 in the MPI world model. At  the  moment  when	 the  last  process  calls
       MPI_Finalize,  all  pending  sends  in  the  MPI	 world model must be matched by a receive, and all pending
       receives in the MPI world model must be matched by a send.

       See MPI-5.0:11.4.1 <https://www.mpi-forum.org/> for a list of MPI functionality that  is	 available  (e.g.,
       even when the MPI world model has not yet initialized or has already been finalized).

       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
       The MPI session model is different than the MPI world model, and has different scopes of	 availability  for
       MPI    functionality.	 See	MPI_Session_init    <#mpi-session-init>	   and	 MPI_Session_finalize	<#
       mpi-session-finalize>.

       All processes that initialized the MPI world model must call this routine before	 exiting.   All	 processes
       will  still  exist  but	may not make any further MPI calls in the MPI world model. MPI_Finalize guarantees
       that all local actions required by communications in the MPI world model that the user has completed  will,
       in  fact, occur before it returns. However, MPI_Finalize guarantees nothing about pending communications in
       the MPI world model that have not been completed; completion is ensured only by	the  MPI_Wait  <#mpi-wait>
       and  MPI_Test  <#mpi-test>  variants,  or  MPI_Request_free  <#mpi-request-free>	 combined  with some other
       verification of completion.

       For example, a successful return from a blocking communication operation or from one  of	 the  MPI_Wait	<#
       mpi-wait>  or  MPI_Test	<#mpi-test> varients 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 <#mpi-request-free> with a request handle generated by an MPI_Isend
       <#mpi-isend> nullifies the handle but does not guarantee that the operation has completed. The MPI_Isend <#
       mpi-isend> is complete only when a matching receive has completed.

       If  you	would  like  to	 cause	actions	 to happen when a process finalizes the MPI world model, 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 <#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 the MPI world model are affected. Calling MPI_Finalized <#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>/MPI_Init_thread <#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	<#
       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>/MPI_Comm_spawn_multiple	<#
       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 <#mpi-abort> was called on that communicator. If called
	 on  a window or file, acts as if MPI_Abort <#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	<#mpi-comm-create-errhandler>	  then	   MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	 <#mpi-file-create-errhandler>	   then	    MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       See the Error Handling section of the MPI-3.1 standard for more information.

       See also:

	  • MPI_Finalized <#mpi-finalized>

	  • MPI_Init <#mpi-init>

	  • MPI_Initialized <#mpi-initialized>

	  • MPI_Session_init <#mpi-session-init>

	  • MPI_Session_finalize <#mpi-session-finalize>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					   MPI_FINALIZE(3)
