1MPI_Bsend(3) LAM/MPI MPI_Bsend(3)
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6 MPI_Bsend - Basic send with user-specified buffering
7
9 #include <mpi.h>
10 int MPI_Bsend(void *buf, int count, MPI_Datatype dtype,
11 int dest, int tag, MPI_Comm comm)
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14 buf - initial address of send buffer (choice)
15 count - number of elements in send buffer (nonnegative integer)
16 dtype - datatype of each send buffer element (handle)
17 dest - rank of destination (integer)
18 tag - message tag (integer)
19 comm - communicator (handle)
20
23 This send is provided as a convenience function; it allows the user to
24 send messages without worring about where they are buffered (because
25 the user must have provided buffer space with MPI_Buffer_attach ).
26 In deciding how much buffer space to allocate, remember that the buffer
28 space is not available for reuse by subsequent MPI_Bsend s unless you
29 are certain that the message has been received (not just that it should
30 have been received). For example, this code does not allocate enough
31 buffer space
32 MPI_Buffer_attach(b, n*sizeof(double) + MPI_BSEND_OVERHEAD);
34 for (i = 0; i < m; i++) {
35 MPI_Bsend(buf, n, MPI_DOUBLE, ...);
36 }
37 because only enough buffer space is provided for a single send, and the
39 loop may start a second MPI_Bsend before the first is done making use
40 of the buffer.
41 In C, you can force the messages to be delivered by
43 MPI_Buffer_detach(&b, &n);
44 MPI_Buffer_attach(b, n);
45 (The MPI_Buffer_detach will not complete until all buffered messages
47 are delivered.)
48 It is generally a bad idea to use the MPI_Bsend function, as it guaran‐
50 tees that the entire message will suffer the overhead of an additional
51 memory copy. For large messages, or when shared memory message trans‐
52 ports are being used, this overhead can be quite expensive.
53
56 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
57 an additional argument ierr at the end of the argument list. ierr is
58 an integer and has the same meaning as the return value of the routine
59 in C. In Fortran, MPI routines are subroutines, and are invoked with
60 the call statement.
61 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
63 Fortran.
64
67 If an error occurs in an MPI function, the current MPI error handler is
68 called to handle it. By default, this error handler aborts the MPI
69 job. The error handler may be changed with MPI_Errhandler_set ; the
70 predefined error handler MPI_ERRORS_RETURN may be used to cause error
71 values to be returned (in C and Fortran; this error handler is less
72 useful in with the C++ MPI bindings. The predefined error handler
73 MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
74 needs to be recovered). Note that MPI does not guarantee that an MPI
75 program can continue past an error.
76 All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
78 value; C routines as the value of the function and Fortran routines in
79 the last argument. The C++ bindings for MPI do not return error val‐
80 ues; instead, error values are communicated by throwing exceptions of
81 type MPI::Exception (but not by default). Exceptions are only thrown
82 if the error value is not MPI::SUCCESS .
83 Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
86 functions will return upon an error, there will be no way to recover
87 what the actual error value was.
88 MPI_SUCCESS
89 - No error; MPI routine completed successfully.
90 MPI_ERR_COMM
91 - Invalid communicator. A common error is to use a null commu‐
92 nicator in a call (not even allowed in MPI_Comm_rank ).
93 MPI_ERR_COUNT
94 - Invalid count argument. Count arguments must be non-negative;
95 a count of zero is often valid.
96 MPI_ERR_TYPE
97 - Invalid datatype argument. May be an uncommitted MPI_Datatype
98 (see MPI_Type_commit ).
99 MPI_ERR_RANK
100 - Invalid source or destination rank. Ranks must be between
101 zero and the size of the communicator minus one; ranks in a
102 receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also
103 be MPI_ANY_SOURCE .
104 MPI_ERR_TAG
106 - Invalid tag argument. Tags must be non-negative; tags in a
107 receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also
108 be MPI_ANY_TAG . The largest tag value is available through the
109 the attribute MPI_TAG_UB .
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114 MPI_Buffer_attach, MPI_Buffer_detach, MPI_Ibsend, MPI_Bsend_init
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118 For more information, please see the official MPI Forum web site, which
119 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
120 ments contain detailed information about each MPI function (most of
121 which is not duplicated in these man pages).
122 http://www.mpi-forum.org/
124
128 The LAM Team would like the thank the MPICH Team for the handy program
129 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
130 ing/sowing.tar.gz ), the initial formatting, and some initial text for
131 most of the MPI-1 man pages.
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134 bsend.c
135LAM/MPI 7.1.2 2/23/2006 MPI_Bsend(3)