.. _mpi_win_attach:


MPI_Win_attach
==============

.. include_body

:ref:`MPI_Win_attach`, :ref:`MPI_Win_detach` - One-sided MPI call that attaches /
detaches a memory region to / from a window object for RMA operations.


SYNTAX
------


C Syntax
^^^^^^^^

.. code-block:: c

   #include <mpi.h>

   MPI_Win_attach(MPI_Win win, void *base, MPI_Aint size)

   MPI_Win_detach(MPI_Win win, void *base)


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

.. code-block:: fortran

   USE MPI
   ! or the older form: INCLUDE 'mpif.h'
   MPI_WIN_ATTACH(WIN, BASE, SIZE, IERROR)
   	<type> BASE(*)
   	INTEGER(KIND=MPI_ADDRESS_KIND) SIZE
   	INTEGER WIN, IERROR

   MPI_WIN_DETACH(WIN, BASE, IERROR)
   	<type> BASE(*)
   	INTEGER WIN, IERROR


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

.. code-block:: fortran

   USE mpi_f08
   MPI_Win_attach(win, base, size, ierror)
   	TYPE(MPI_Win), INTENT(IN) :: win
   	TYPE(*), DIMENSION(..), INTENT(IN) :: base
   	INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: size
   	INTEGER, OPTIONAL, INTENT(OUT) :: ierror

   MPI_Win_detach(win, base, ierror)
   	TYPE(MPI_Win), INTENT(IN) :: win
   	TYPE(*), DIMENSION(..), INTENT(IN) :: base
   	INTEGER, OPTIONAL, INTENT(OUT) :: ierror


INPUT PARAMETERS
----------------
* ``win``: A window that was created with *MPI_Win_create_dynamic*
* ``base``: Initial address of window (choice).
* ``size``: Size of window in bytes (nonnegative integer).

OUTPUT PARAMETERS
-----------------
* ``win``: Window object returned by the call (handle).
* ``IERROR``: Fortran only: Error status (integer).

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

:ref:`MPI_Win_attach` is a one-sided MPI communication call used to attach a
memory region of *size* bytes starting at address *base* to a window for
RMA access. The window *win* must have been created using
:ref:`MPI_Win_create_dynamic`. Multiple non-overlapping memory regions may be
attached to the same dynamic window. Attaching overlapping memory
regions to the same dynamic window is erroneous.

If the *base* value used by :ref:`MPI_Win_attach` was allocated by
:ref:`MPI_Alloc_mem`, the size of the window can be no larger than the value
set by the :ref:`MPI_ALLOC_MEM` function.

:ref:`MPI_Win_detach` can be used to detach a previously attached memory region
from *win*. The memory address *base* and *win* must match arguments
passed to a previous call to :ref:`MPI_Win_attach`.


NOTES
-----

Use memory allocated by :ref:`MPI_Alloc_mem` to guarantee properly aligned
window boundaries (such as word, double-word, cache line, page frame,
and so on).


ERRORS
------

Almost all MPI routines return an error value; C routines as the value
of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with
:ref:`MPI_Comm_set_errhandler`; the predefined error handler MPI_ERRORS_RETURN
may be used to cause error values to be returned. Note that MPI does not
guarantee that an MPI program can continue past an error.
