1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
|
.\" Man page generated from reStructuredText.
.
.TH "MPI_BUFFER_DETACH" "3" "May 30, 2025" "" "Open MPI"
.
.nr rst2man-indent-level 0
.
.de1 rstReportMargin
\\$1 \\n[an-margin]
level \\n[rst2man-indent-level]
level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
-
\\n[rst2man-indent0]
\\n[rst2man-indent1]
\\n[rst2man-indent2]
..
.de1 INDENT
.\" .rstReportMargin pre:
. RS \\$1
. nr rst2man-indent\\n[rst2man-indent-level] \\n[an-margin]
. nr rst2man-indent-level +1
.\" .rstReportMargin post:
..
.de UNINDENT
. RE
.\" indent \\n[an-margin]
.\" old: \\n[rst2man-indent\\n[rst2man-indent-level]]
.nr rst2man-indent-level -1
.\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
.in \\n[rst2man-indent\\n[rst2man-indent-level]]u
..
.sp
\fI\%MPI_Buffer_detach\fP — Removes an existing buffer (for use in in \fI\%MPI_Bsend\fP,
etc.)
.SH SYNTAX
.SS C Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#include <mpi.h>
int MPI_Buffer_detach(void *buf, int *size)
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
USE MPI
! or the older form: INCLUDE \(aqmpif.h\(aq
MPI_BUFFER_DETACH(BUF, SIZE, IERROR)
<type> BUF(*)
INTEGER SIZE, IERROR
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran 2008 Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
USE mpi_f08
MPI_Buffer_detach(buffer_addr, size, ierror)
USE, INTRINSIC :: ISO_C_BINDING, ONLY
TYPE(C_PTR), INTENT(OUT) :: buffer_addr
INTEGER, INTENT(OUT) :: size
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
.ft P
.fi
.UNINDENT
.UNINDENT
.SH OUTPUT PARAMETERS
.INDENT 0.0
.IP \(bu 2
\fBbuf\fP : Initial buffer address (choice).
.IP \(bu 2
\fBsize\fP : Buffer size, in bytes (integer).
.IP \(bu 2
\fBierror\fP : Fortran only: Error status (integer).
.UNINDENT
.SH DESCRIPTION
.sp
Detach the buffer currently associated with MPI. The call returns the
address and the size of the detached buffer. This operation will block
until all messages currently in the buffer have been transmitted. Upon
return of this function, the user may reuse or deallocate the space
taken by the buffer.
.sp
Example: Calls to attach and detach buffers.
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#define BUFFSIZE 10000
int size char *buff;
MPI_Buffer_attach( malloc(BUFFSIZE), BUFFSIZE);
// a buffer of 10000 bytes can now be used by MPI_Bsend
MPI_Buffer_detach( &buff, &size); // Buffer size reduced to zero
MPI_Buffer_attach( buff, size); // Buffer of 10000 bytes available again
.ft P
.fi
.UNINDENT
.UNINDENT
.SH NOTES
.sp
The reason that \fI\%MPI_Buffer_detach\fP returns the address and size of the
buffer being detached is to allow nested libraries to replace and
restore the buffer. For example, consider
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
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 );
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
This is much like the action of the UNIX signal routine and has the same
strengths (it’s simple) and weak‐nesses (it only works for nested
usages).
.sp
For 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.
.sp
For C: Even though the buf argument is declared as void, it is really
the address of a void pointer. See Rationale, below, for more details.
.sp
Even though the C functions \fI\%MPI_Buffer_attach\fP and \fI\%MPI_Buffer_detach\fP both
have a first argument of type void*, these arguments are used
differently: A pointer to the buffer is passed to \fI\%MPI_Buffer_attach\fP; the
address of the pointer is passed to \fI\%MPI_Buffer_detach\fP, so that this call
can return the pointer value.
.SH ERRORS
.sp
Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.
.sp
Before the error value is returned, the current MPI error handler associated
with the communication object (e.g., communicator, window, file) is called.
If no communication object is associated with the MPI call, then the call is
considered attached to MPI_COMM_SELF and will call the associated MPI error
handler. When MPI_COMM_SELF is not initialized (i.e., before
\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error
handler is called for all other MPI functions.
.sp
Open MPI includes three predefined error handlers that can be used:
.INDENT 0.0
.IP \(bu 2
\fBMPI_ERRORS_ARE_FATAL\fP
Causes the program to abort all connected MPI processes.
.IP \(bu 2
\fBMPI_ERRORS_ABORT\fP
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if \fI\%MPI_Abort\fP was called on that communicator. If
called on a window or file, acts as if \fI\%MPI_Abort\fP was called
on a communicator containing the group of processes in the
corresponding window or file. If called on a session,
aborts only the local process.
.IP \(bu 2
\fBMPI_ERRORS_RETURN\fP
Returns an error code to the application.
.UNINDENT
.sp
MPI applications can also implement their own error handlers by calling:
.INDENT 0.0
.IP \(bu 2
\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
.IP \(bu 2
\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
.UNINDENT
.sp
Note that MPI does not guarantee that an MPI program can continue past
an error.
.sp
See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
.sp
See the Error Handling section of the MPI\-3.1 standard for
more information.
.sp
\fBSEE ALSO:\fP
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.IP \(bu 2
\fI\%MPI_Buffer_attach\fP
.UNINDENT
.UNINDENT
.UNINDENT
.SH COPYRIGHT
2003-2025, The Open MPI Community
.\" Generated by docutils manpage writer.
.
|
