MPI\_SESSION\_FINALIZE(3) Open MPI MPI\_SESSION\_FINALIZE(3) MPI\_Session\_finalize — releases all MPI state associated with a session # [SYNTAX](#SYNTAX) ## [C Syntax](#C_Syntax) ``` #include int MPI_Session_finalize(MPI_Session *session) ``` ## [Fortran Syntax](#Fortran_Syntax) ``` USE MPI ! or the older form: INCLUDE 'mpif.h' MPI_SESSION_FINALIZE(SESSION, IERROR) INTEGER SESSION, IERROR ``` ## [Fortran 2008 Syntax](#Fortran_2008_Syntax) ``` USE mpi_f08 MPI_Session_finalize(session, ierror) TYPE(MPI_Session), INTENT(IN) :: session INTEGER, OPTIONAL, INTENT(OUT) :: ierror ``` # [INPUT PARAMETERS](#INPUT_PARAMETERS) • **session** : session to be finalized (handle) # [OUTPUT PARAMETERS](#OUTPUT_PARAMETERS) • **ierror** : Fortran only: Error status (integer). # [DESCRIPTION](#DESCRIPTION) MPI\_Session\_finalize releases all MPI state associated with the supplied session. Every instantiated session must be finalized using MPI\_Session\_finalize. The handle session is set to **MPI\_SESSION\_NULL** by the call. Multiple sessions can be created and destroyed during the lifetime of an MPI process. This is different than MPI world model, which can be initialized at most exactly once (and then subsequently finalized) during the lifetime of an MPI process. # [NOTES](#NOTES) Before an MPI process invokes MPI\_Session\_finalize, the process must perform all MPI calls needed to complete its involvement in MPI communications: it must locally complete all MPI operations that it initiated and it must execute matching calls needed to complete MPI communications initiated by other processes. The call to MPI\_Session\_finalize does not free objects created by MPI calls; these objects are freed using MPI\_XXX\_FREE calls. MPI\_Session\_finalize may be synchronizing on any or all of the groups associated with communicators, windows, or files derived from the session and not disconnected, freed, or closed, respectively, before the call to MPI\_Session\_finalize procedure. MPI\_Session\_finalize behaves as if all such synchronizations occur concurrently. As MPI\_Comm\_free <#mpi-comm-free> may mark a communicator for freeing later, MPI\_Session\_finalize may be synchronizing on the group associated with a communicator that is only freed (with MPI\_Comm\_free) rather than disconnected (with MPI\_Comm\_disconnect). # [ERRORS](#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 <#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\_Init <#mpi-init> - MPI\_Initialized <#mpi-initialized> - MPI\_Init\_thread <#mpi-init-thread> - MPI\_Finalize <#mpi-finalize> - MPI\_Finalized <#mpi-finalized> - MPI\_Session\_init <#mpi-session-init> # [Copyright](#Copyright) 2003-2026, The Open MPI Community September 16, 2026 --- Document: MPI_Session_finalize(3) from openmpi-cuda-12.8 5.0.11-r1 (Chainguard OS) Source: https://github.com/open-mpi/ompi