MPI_COMM_FREE(3)

MPI_Comm_free — Mark a communicator object for deallocation.

SYNTAX

  C Syntax

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

  Fortran Syntax

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

  Fortran 2008 Syntax

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

INPUT PARAMETER

•   comm: Communicator to be destroyed (handle).

OUTPUT PARAMETER

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

DESCRIPTION

This operation marks the communicator object for deallocation. The handle is set to MPI_COMM_NULL. Any pending operations that use this communicator will complete normally; the object is actually deallocated only if there are no other active references to it. This call applies to intracommunicators and intercommunicators. Upon actual deallocation, the delete callback functions for all cached attributes (see the “Caching” section in the “Groups, Contexts, and Communicators” chapter in the MPI Standard) are called in arbitrary order.

NOTES

Note that it is not defined by the MPI standard what happens if the delete_fn callback invokes other MPI functions. In Open MPI, it is not valid for delete_fn callbacks (or any of their children) to add or delete attributes on the same object on which the delete_fn callback is being invoked.

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_delete_attr

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