NAME

       MPI_Buffer_attach -  Attaches a user-provided buffer for sending

SYNOPSIS

       int MPI_Buffer_attach(void *buffer, int size)

INPUT PARAMETERS

       buffer - initial buffer address (choice)
       size   - buffer size, in bytes (integer)

NOTES

       The  size  given  should  be the sum of the sizes of all outstanding Bsends that you intend to have, plus
       MPI_BSEND_OVERHEAD 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( buffer, 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;

       The  MPI_BSEND_OVERHEAD  gives  the maximum amount of space that may be used in the buffer for use by the
       BSEND routines in using the buffer.  This value is in mpi.h (for C) and mpif.h (for Fortran).

THREAD AND INTERRUPT SAFETY

       The user is responsible for ensuring that multiple threads do not try to update the same MPI object  from
       different threads.  This routine should not be used from within a signal handler.

       The  MPI  standard defined a thread-safe interface but this does not mean that all routines may be called
       without any thread locks.  For example, two threads must not attempt to change the contents of  the  same
       MPI_Info  object  concurrently.   The  user is responsible in this case for using some mechanism, such as
       thread locks, to ensure that only one thread at a time makes use of this routine.  Because the buffer for
       buffered  sends  (e.g.,  MPI_Bsend  )  is shared by all threads in a process, the user is responsible for
       ensuring that only one thread at a time calls this routine or MPI_Buffer_detach .

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the
       end of the argument list.  ierr is an integer and has the same meaning as the return value of the routine
       in C.  In Fortran, MPI routines are subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of  the
       function  and Fortran routines in the last argument.  Before the value is returned, the current MPI error
       handler is called.  By default, this error handler aborts the MPI job.  The error handler may be  changed
       with    MPI_Comm_set_errhandler   (for   communicators),   MPI_File_set_errhandler   (for   files),   and
       MPI_Win_set_errhandler (for RMA windows).  The MPI-1 routine MPI_Errhandler_set may be used but  its  use
       is  deprecated.   The  predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be
       returned.  Note that MPI does not guarentee that an MPI program can continue past an error; however,  MPI
       implementations will attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_BUFFER
              - Invalid buffer pointer.  Usually a null buffer where one is not valid.
       MPI_ERR_INTERN
              -  An  internal  error  has  been  detected.   This  is  fatal.   Please send a bug report to mpi-
              bugs@mcs.anl.gov .

SEE ALSO

       MPI_Buffer_detach, MPI_Bsend

LOCATION

       src/mpi/pt2pt/bufattach.c

                                                    4/24/2013                               MPI_Buffer_attach(3)