.. _mpi_comm_delete_attr:

MPI_Comm_delete_attr
====================

.. include_body

:ref:`MPI_Comm_delete_attr` |mdash| Deletes attribute value associated with a
key.

SYNTAX
------

C Syntax
^^^^^^^^

.. code-block:: c

   #include <mpi.h>

   int MPI_Comm_delete_attr(MPI_Comm comm, int comm_keyval)

Fortran Syntax
^^^^^^^^^^^^^^

.. code-block:: fortran

   USE MPI
   ! or the older form: INCLUDE 'mpif.h'

   MPI_COMM_DELETE_ATTR(COMM, COMM_KEYVAL, IERROR)
       INTEGER COMM, COMM_KEYVAL, IERROR

Fortran 2008 Syntax
^^^^^^^^^^^^^^^^^^^

.. code-block:: fortran

   USE mpi_f08

   MPI_Comm_delete_attr(comm, comm_keyval, ierror)
       TYPE(MPI_Comm), INTENT(IN) :: comm
       INTEGER, INTENT(IN) :: comm_keyval
       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT/OUTPUT PARAMETER
^^^^^^^^^^^^^^^^^^^^^^

* ``comm`` : Communicator from which the attribute is deleted (handle).

INPUT PARAMETER
---------------

* ``comm_keyval`` : Key value (integer).

OUTPUT PARAMETER
----------------

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

DESCRIPTION
-----------

:ref:`MPI_Comm_delete_attr` deletes an attribute from cache by key. This
function invokes the attribute delete function ``delete_fn`` specified
when the ``comm_keyval`` was created. The call will fail if the
``delete_fn`` function returns an error code other than ``MPI_SUCCESS``.

Whenever a communicator is replicated using the function
:ref:`MPI_Comm_dup`, all callback copy functions for attributes that are
currently set are invoked (in arbitrary order). Whenever a communicator
is deleted using the function :ref:`MPI_Comm_free`, all callback delete
functions for attributes that are currently set are invoked. This
function is the same as :ref:`MPI_Attr_delete` but is needed to match the
``comm``\ unicator-specific functions introduced in the MPI-2 standard.
The use of :ref:`MPI_Attr_delete` is deprecated.

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
------

.. include:: ./ERRORS.rst