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MPI_Buffer_detach(3)			     LAM/MPI			     MPI_Buffer_detach(3)

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

       #include <mpi.h>
       int MPI_Buffer_detach(void *pbuf, int *psize)

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

       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,

       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 stan-
       dard 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

       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.

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argu-
       ment 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  point-
       ers,  it is impossible to provide a way to use the output of this routine to exchange buf-
       fers.  In this case, only the size field is set.

       Even though the pbuf argument is declared as void * , it is really the address of  a  void
       pointer (i.e., void ** ).  See the rationale in the MPI Standard for more details.

       For  more information, please see the official MPI Forum web site, which contains the text
       of both the MPI-1 and MPI-2 standards.  These documents contain detailed information about
       each MPI function (most of which is not duplicated in these man pages).


       The  LAM  Team  would  like the thank the MPICH Team for the handy program to generate man
       pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz ), the  initial  for-
       matting, and some initial text for most of the MPI-1 man pages.


LAM/MPI 6.5.8				    11/10/2002			     MPI_Buffer_detach(3)
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