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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++ 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




Open MPI 1.2                                   September 2006                    MPI_Buffer_attach(3OpenMPI)