.. _mpi_comm_idup_with_info:


MPI_Comm_idup_with_info
=======================

.. include_body

:ref:`MPI_Comm_idup_with_info` |mdash| Start the nonblocking duplication of an
existing communicator with all its cached information.


SYNTAX
------


C Syntax
^^^^^^^^

.. code-block:: c

   #include <mpi.h>

   int MPI_Comm_idup_with_info(MPI_Comm comm, MPI_Info info, MPI_Comm *newcomm, MPI_Request *request)


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

.. code-block:: fortran

   USE MPI
   ! or the older form: INCLUDE 'mpif.h'
   MPI_COMM_IDUP_WITH_INFO(COMM, INFO, NEWCOMM, REQUEST, IERROR)
       INTEGER    COMM, INFO, NEWCOMM, REQUEST, IERROR


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

.. code-block:: fortran

   USE mpi_f08
   MPI_Comm_idup_with_info(comm, info, newcomm, request, ierror)
       TYPE(MPI_Comm), INTENT(IN) :: comm
       TYPE(MPI_Info), INTENT(IN) :: info
       TYPE(MPI_Comm), INTENT(OUT) :: newcomm
       TYPE(MPI_Request), INTENT(OUT) :: request
       INTEGER, OPTIONAL, INTENT(OUT) :: ierror


INPUT PARAMETER
---------------
* ``comm``: Communicator (handle). info Info object (handle).

OUTPUT PARAMETERS
-----------------
* ``newcomm``: Copy of comm (handle).
* ``request``: Communication request (handle).
* ``ierror``: Fortran only: Error status (integer).

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

:ref:`MPI_Comm_idup_with_info` starts the nonblocking duplication of an
existing communicator comm with associated key values. For each key
value, the respective copy callback function determines the attribute
value associated with this key in the new communicator; one particular
action that a copy callback may take is to delete the attribute from the
new communicator. Returns in newcomm a new communicator with the same
group, any copied cached information, but a new context
(see the "Functionality" subsection of the "Caching"
section in the "Groups, Contexts, and Communicators" chapter in the
`MPI Standard <https://www.mpi-forum.org/docs/>`_).  The communicator returned
in *newcomm* will not be available until the request is complete. The
hints provided by the supplied *info* argument are associated with the
output communicator.

The completion of a communicator duplication request can be determined
by calling any of :ref:`MPI_Wait`, :ref:`MPI_Waitany`, :ref:`MPI_Test`, or :ref:`MPI_Testany` with
the request returned by this function.


NOTES
-----

This operation is used to provide a parallel library call with a
duplicate communication space that has the same properties as the
original communicator. This includes any attributes (see below) and
topologies (see the "Process Topologies" chapter in the `MPI Standard
<https://www.mpi-forum.org/docs/>`_).
This call is valid even if there are pending point-to-point
communications involving the communicator comm. A typical call might
involve an :ref:`MPI_Comm_idup_with_info` at the beginning of the parallel
call, and an :ref:`MPI_Comm_free` of that duplicated communicator at the end of
the call. Other models of communicator management are also possible.

This call applies to both intra- and intercommunicators.

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


ERRORS
------

.. include:: ./ERRORS.rst

.. seealso::
   * :ref:`MPI_Comm_dup`
   * :ref:`MPI_Comm_idup`
   * :ref:`MPI_Comm_dup_with_info`
