MPI_Buffer_detach - Removes an existing buffer (for use in MPI_Bsend
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, consider
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
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
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 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
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 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
formatting, and some initial text for most of the MPI-1 man pages.