MPI_Buffer_attach(3)               Open MPI               MPI_Buffer_attach(3)



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++
       functions 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




1.4.1                            Jan 14, 2010             MPI_Buffer_attach(3)
