NAME

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

SYNOPSIS

       int MPI_Buffer_detach(void *buffer_addr, int *size)

OUTPUT PARAMETERS

       buffer_addr
              - 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

                                            11/12/2016                       MPI_Buffer_detach(3)