oracular (3) MPI_Buffer_attach.openmpi.3.gz

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

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_BUFFER_ATTACH(BUF, SIZE, IERROR)
            <type>    BUF(*)
            INTEGER   SIZE, IERROR

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Buffer_attach(buffer, size, ierror)
            TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buffer
            INTEGER, INTENT(IN) :: size
            INTEGER, OPTIONAL, INTENT(OUT) :: 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