doc: Add MPI-4.0 partial compliance features

Signed-off-by: William Zhang <[email protected]>

Author: wckzhang

docs/release-notes/mpi.rst

@@ -31,6 +31,36 @@ For historical reference:
    * - MPI-3.1
      - Open MPI v2.0
 
+MPI-4.0 partial compliance
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In the Open MPI |ompi_series| series, only partial MPI-4.0 functionality is
+supported. This section contains a list of features added for the release.
+
+* Added support for MPI Sessions.
+* Added partitioned communication using persistent sends and persistent receives.
+* Added persistent collectives to the ``MPI_`` namespace (they were previously
+  available via the ``MPIX_ prefix``).
+* Added support for :ref:`MPI_Isendrecv()<mpi_isendrecv>` and its variants.
+* Added support for :ref:`MPI_Comm_idup_with_info()<mpi_comm_idup_with_info>`.
+* Added support for :ref:`MPI_Info_get_string()<mpi_info_get_string>`.
+* Added support for ``initial_error_handler`` and the :doc:`ERRORS_ABORT</man-openmpi/man3/ERRORS>`
+  infrastructure.
+* Added support for mpi_minimum_alignment info key
+* Added support for ``MPI_COMM_TYPE_HW_GUIDED`` and
+  ``MPI_COMM_TYPE_HW_UNGUIDED`` added.
+* Added support for :ref:`MPI_Info_create_env()<mpi_info_create_env>`.
+* Added error handling for “unbound” errors to ``MPI_COMM_SELF``.
+* Added ``MPI_F_STATUS_SIZE``, ``MPI_F_SOURCE``, ``MPI_F_TAG``, and ``MPI_F_ERROR``
+* Made :ref:`MPI_Comm_get_info()<mpi_comm_get_info>`,
+  :ref:`MPI_File_get_info()<mpi_file_get_info>`, and
+  :ref:`MPI_Win_get_info()<mpi_win_get_info>` MPI 4.0 compliant
+* Info keys that are not understood by Open MPI will be silently ignored and
+  dropped on communicators, files, and windows.
+* Deprecated :ref:`MPI_Sizeof()<mpi_sizeof>`.
+* Deprecated :ref:`MPI_Cancel()<mpi_cancel>` on send requests.
+* Deprecated :ref:`MPI_Info_get()<mpi_info_get>` and :ref:`MPI_Info_get_valuelen()<mpi_info_get_valuelen>`
+
 Removed MPI APIs
 ----------------