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MPI_Buffer_detach(3)                  MPI                 MPI_Buffer_detach(3)

NAME
       MPI_Buffer_detach -  Removes an existing buffer (for use in MPI_Bsend
       etc)

SYNOPSIS
       int MPI_Buffer_detach(void *buffer, int *size)

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

NOTES
       The reason that MPI_Buffer_detach returns the address and size of the
       buffer being detached is to allow nested libraries to replace and
       restore the buffer.  For example, consider

       int size, mysize, idummy;
       void *ptr, *myptr, *dummy;
       MPI_Buffer_detach( &ptr, &size );
       MPI_Buffer_attach( myptr, mysize );
       .
       .
       .
       .
       .
       .
       library code ...
       .
       .
       .
       MPI_Buffer_detach( &dummy, &idummy );
       MPI_Buffer_attach( ptr, size );

       This is much like the action of the Unix signal routine and has the
       same strengths (it is simple) and weaknesses (it only works for nested
       usages).

       Note that for this approach to work, MPI_Buffer_detach must return
       MPI_SUCCESS even when there is no buffer to detach.  In that case, it
       returns a size of zero.  The MPI 1.1 standard for MPI_BUFFER_DETACH
       contains the text

       The statements made in this section describe the behavior of MPI for
       buffered-mode sends. When no buffer is currently associated, MPI behaves
       as if a zero-sized buffer is associated with the process.

       This could be read as applying only to the various Bsend routines.
       This implementation takes the position that this applies to
       MPI_BUFFER_DETACH as well.

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_attach .

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.

       The Fortran binding for this routine is different.  Because Fortran
       does not have pointers, it is impossible to provide a way to use the
       output of this routine to exchange buffers.  In this case, only the
       size field is set.

NOTES FOR C
       Even though the bufferptr argument is declared as void * , it is really
       the address of a void pointer.  See the rationale in the standard for
       more details.

SEE ALSO
       MPI_Buffer_attach

LOCATION
       src/mpi/pt2pt/buffree.c

                                   9/20/2012              MPI_Buffer_detach(3)