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.. _mpi_buffer_attach:
MPI_Buffer_attach
=================
.. include_body
:ref:`MPI_Buffer_attach` |mdash| Attaches a user-defined buffer for sending.
SYNTAX
------
C Syntax
^^^^^^^^
.. code-block:: C
#include <mpi.h>
int MPI_Buffer_attach(void *buf, int size)
Fortran Syntax
^^^^^^^^^^^^^^
.. code-block:: Fortran
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_BUFFER_ATTACH(BUF, SIZE, IERROR)
<type> BUF(*)
INTEGER SIZE, IERROR
Fortran 2008 Syntax
^^^^^^^^^^^^^^^^^^^
.. code-block:: Fortran
USE mpi_f08
MPI_Buffer_attach(buffer, size, ierror)
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buffer
INTEGER, INTENT(IN) :: size
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
INPUT PARAMETERS
----------------
* ``buf`` : Initial buffer address (choice).
* ``size`` : Buffer size, in bytes (integer).
OUTPUT PARAMETER
----------------
* ``ierror`` : Fortran only: Error status (integer).
DESCRIPTION
-----------
Provides to MPI a buffer in the user's memory to be used for buffering
outgoing messages. The buffer is used only by messages sent in buffered
mode. Only one buffer can be attached to a process at a time.
NOTES
-----
The size given should be the sum of the sizes of all outstanding Bsends
that you intend to have, plus MPI_BSEND_OVERHEAD bytes for each Bsend
that you do. For the purposes of calculating size, you should use
:ref:`MPI_Pack_size`. In other words, in the code
.. code-block:: c
MPI_Buffer_attach( buf, size )
MPI_Bsend( ..., count=20, datatype=type1, ... );
MPI_Bsend( ..., count=40, datatype=type2, ... );
the value of size in the :ref:`MPI_Buffer_attach` call should be greater than
the value computed by
.. code-block:: c
MPI_Pack_size( 20, type1, comm, &s1 );
MPI_Pack_size( 40, type2, comm, &s2 );
size = s1 + s2 + 2 * MPI_BSEND_OVERHEAD;
MPI_BSEND_OVERHEAD gives the maximum amount of buffer space that may be
used by the Bsend routines. This value is in mpi.h for C and mpif.h for
Fortran.
ERRORS
------
.. include:: ./ERRORS.rst
.. seealso::
* :ref:`MPI_Buffer_detach`
|
