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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 re-
       store 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_BUF-
       FER_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)

NAME | SYNOPSIS | OUTPUT PARAMETERS | NOTES | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | NOTES FOR C | SEE ALSO | LOCATION

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