---
name: "MPI_Comm_disconnect"
section: "3"
platform: "linux"
package: "openmpi"
version: "5.0.11-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/MPI_Comm_disconnect"
---

# MPI\_Comm\_disconnect(3)

*MPI\_Comm\_disconnect* — Deallocates communicator object and sets handle to MPI\_COMM\_NULL.

## SYNTAX

### C Syntax

```
#include <mpi.h>
int MPI_Comm_disconnect(MPI_Comm *comm)
```

### Fortran Syntax

```
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_DISCONNECT(COMM, IERROR)
    INTEGER COMM, IERROR
```

### Fortran 2008 Syntax

```
USE mpi_f08
MPI_Comm_disconnect(comm, ierror)
    TYPE(MPI_Comm), INTENT(INOUT) :: comm
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror
```

### INPUT/OUTPUT PARAMETER

- •

  **comm** : Communicator (handle).

## OUTPUT PARAMETER

- •

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

## DESCRIPTION

*MPI\_Comm\_disconnect* waits for all pending communication on comm to complete internally, deallocates the communicator object, and sets the handle to MPI\_COMM\_NULL. It is a collective operation. It may not be called with the communicator MPI\_COMM\_WORLD or MPI\_COMM\_SELF. *MPI\_Comm\_disconnect* may be called only if all communication is complete and matched, so that buffered data can be delivered to its destination. This requirement is the same as for *MPI\_Finalize*. *MPI\_Comm\_disconnect* has the same action as *MPI\_Comm\_free*, except that it waits for pending communication to finish internally and enables the guarantee about the behavior of disconnected processes.

## NOTES

To disconnect two processes you may need to call *MPI\_Comm\_disconnect*, *MPI\_Win\_free*, and *MPI\_File\_close* to remove all communication paths between the two processes. Note that it may be necessary to disconnect several communicators (or to free several windows or files) before two processes are completely independent.

## 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\_Comm\_connect*

## COPYRIGHT

2003-2026, The Open MPI Community