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.. _mpi_pack:
MPI_Pack
========
.. include_body
:ref:`MPI_Pack` |mdash| Packs data of a given datatype into contiguous memory.
SYNTAX
------
C Syntax
^^^^^^^^
.. code-block:: c
#include <mpi.h>
int MPI_Pack(const void *inbuf, int incount, MPI_Datatype datatype,
void *outbuf, int outsize, int *position, MPI_Comm comm)
Fortran Syntax
^^^^^^^^^^^^^^
.. code-block:: fortran
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_PACK(INBUF, INCOUNT, DATATYPE, OUTBUF,OUTSIZE, POSITION,
COMM, IERROR)
<type> INBUF(*), OUTBUF(*)
INTEGER INCOUNT, DATATYPE, OUTSIZE, POSITION, COMM, IERROR
Fortran 2008 Syntax
^^^^^^^^^^^^^^^^^^^
.. code-block:: fortran
USE mpi_f08
MPI_Pack(inbuf, incount, datatype, outbuf, outsize, position, comm, ierror)
TYPE(*), DIMENSION(..), INTENT(IN) :: inbuf
TYPE(*), DIMENSION(..) :: outbuf
INTEGER, INTENT(IN) :: incount, outsize
TYPE(MPI_Datatype), INTENT(IN) :: datatype
INTEGER, INTENT(INOUT) :: position
TYPE(MPI_Comm), INTENT(IN) :: comm
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
INPUT PARAMETERS
----------------
* ``inbuf``: Input buffer start (choice).
* ``incount``: Number of input data items (integer).
* ``datatype``: Datatype of each input data item (handle).
* ``outsize``: Output buffer size, in bytes (integer).
* ``comm``: Communicator for packed message (handle).
INPUT/OUTPUT PARAMETER
----------------------
* ``position``: Current position in buffer, in bytes (integer).
OUTPUT PARAMETERS
-----------------
* ``outbuf``: Output buffer start (choice).
* ``ierror``: Fortran only: Error status (integer).
DESCRIPTION
-----------
Packs the message in the send buffer specified by *inbuf*, *incount*,
*datatype* into the buffer space specified by *outbuf* and *outsize*.
The input buffer can be any communication buffer allowed in :ref:`MPI_Send`.
The output buffer is a contiguous storage area containing *outsize*
bytes, starting at the address *outbuf* (length is counted in bytes, not
elements, as if it were a communication buffer for a message of type
MPI_Packed).
The input value of *position* is the first location in the output buffer
to be used for packing. *position* is incremented by the size of the
packed message, and the output value of *position* is the first location
in the output buffer following the locations occupied by the packed
message. The *comm* argument is the communicator that will be
subsequently used for sending the packed message.
**Example:** An example using :ref:`MPI_Pack`:
.. code-block:: c
int myrank, position, i, j, a[2];
char buff[1000];
// ...
MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
if (myrank == 0) {
/* SENDER CODE */
position = 0;
MPI_Pack(&i, 1, MPI_INT, buff, 1000, &position, MPI_COMM_WORLD);
MPI_Pack(&j, 1, MPI_INT, buff, 1000, &position, MPI_COMM_WORLD);
MPI_Send(buff, position, MPI_PACKED, 1, 0, MPI_COMM_WORLD);
} else {
/* RECEIVER CODE */
MPI_Recv(a, 2, MPI_INT, 0, 0, MPI_COMM_WORLD);
}
ERRORS
------
.. include:: ./ERRORS.rst
.. seealso::
* :ref:`MPI_Unpack`
* :ref:`MPI_Pack_size`
|
