---
name: "MPI_Finalize.openmpi"
section: "3"
platform: "linux"
package: "openmpi-doc"
version: "5.0.7-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/MPI_Finalize.openmpi"
---

# MPI\_Finalize.openmpi(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*

## COPYRIGHT

2003-2025, The Open MPI Community