MPI_Buffer_detach(3) LAM/MPI MPI_Buffer_detach(3)
MPI_Buffer_detach - Removes an existing buffer (for use in MPI_Bsend etc)
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;
// ...library code...
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.
NOTES FOR FORTRAN
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.
NOTES FOR C
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)