MPI_Buffer_attach(3OpenMPI)											       MPI_Buffer_attach(3OpenMPI)

NAME

       MPI_Buffer_attach - Attaches a user-defined buffer for sending.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Buffer_attach(void *buf, int size)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_BUFFER_ATTACH(BUF, SIZE, IERROR)
	    <type>    BUF(*)
	    INTEGER   SIZE, IERROR

C++ Syntax
       #include <mpi.h>
       void Attach_buffer(void* buffer, int size)

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 MPI_Pack_size. In other words, in the code

	   MPI_Buffer_attach( buf, size );
	   MPI_Bsend( ..., count=20, datatype=type1, ... );
	   ...
	   MPI_Bsend( ..., count=40, datatype=type2, ... );

       the value of size in the MPI_Buffer_attach call should be greater than the value computed by

	   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

       Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func-
       tions  do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       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 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.

SEE ALSO

       MPI_Buffer_detach

Open MPI 1.2							  September 2006				       MPI_Buffer_attach(3OpenMPI)