1MPI_Buffer_detach(3) LAM/MPI MPI_Buffer_detach(3)
2
6 MPI_Buffer_detach - Removes an existing buffer (for use in MPI_Bsend
7 etc)
8
10 #include <mpi.h>
11 int MPI_Buffer_detach(void *pbuf, int *psize)
12
14 pbuf - initial buffer address (choice)
15 psize - buffer size, in bytes (integer)
16
19 The reason that MPI_Buffer_detach returns the address and size of the
20 buffer being detached is to allow nested libraries to replace and
21 restore the buffer. For example, consider
22 int size, mysize, idummy;
24 void *ptr, *myptr, *dummy;
25 MPI_Buffer_detach(&ptr, &size);
26 MPI_Buffer_attach(myptr, mysize);
27 // ...library code...
28 MPI_Buffer_detach(&dummy, &idummy);
29 MPI_Buffer_attach(ptr, size);
30 This is much like the action of the Unix signal routine and has the
33 same strengths (it is simple) and weaknesses (it only works for nested
34 usages).
35 Note that for this approach to work, MPI_Buffer_detach must return
37 MPI_SUCCESS even when there is no buffer to detach. In that case, it
38 returns a size of zero. The MPI 1.1 standard for MPI_BUFFER_DETACH
39 contains the text
40 The statements made in this section describe the behavior of MPI
42 for buffered-mode sends. When no buffer is currently associated,
43 MPI behaves as if a zero-sized buffer is associated with the
44 process.
45 This could be read as applying only to the various Bsend routines.
48 This implementation takes the position that this applies to MPI_BUF‐
49 FER_DETACH as well.
50
53 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
54 an additional argument ierr at the end of the argument list. ierr is
55 an integer and has the same meaning as the return value of the routine
56 in C. In Fortran, MPI routines are subroutines, and are invoked with
57 the call statement.
58 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
60 Fortran.
61 The Fortran binding for this routine is different. Because Fortran
63 does not have pointers, it is impossible to provide a way to use the
64 output of this routine to exchange buffers. In this case, only the
65 size field is set.
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69 Even though the pbuf argument is declared as void * , it is really the
70 address of a void pointer (i.e., void ** ). See the rationale in the
71 MPI Standard for more details.
72
75 For more information, please see the official MPI Forum web site, which
76 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
77 ments contain detailed information about each MPI function (most of
78 which is not duplicated in these man pages).
79 http://www.mpi-forum.org/
81
85 The LAM Team would like the thank the MPICH Team for the handy program
86 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
87 ing/sowing.tar.gz ), the initial formatting, and some initial text for
88 most of the MPI-1 man pages.
89
91 bufdetach.c
92LAM/MPI 7.1.2 2/23/2006 MPI_Buffer_detach(3)