1MPI_Sendrecv_replace(3) LAM/MPI MPI_Sendrecv_replace(3)
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6 MPI_Sendrecv_replace - Sends and receives using a single buffer
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9 #include <mpi.h>
10 int MPI_Sendrecv_replace(void *buf, int count,
11 MPI_Datatype dtype, int dest, int stag,
12 int src, int rtag, MPI_Comm comm,
13 MPI_Status *status)
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16 count - number of elements in send and receive buffer (integer)
17 dtype - type of elements in send and receive buffer (handle)
18 dest - rank of destination (integer)
19 stag - send message tag (integer)
20 src - rank of source (integer)
21 rtag - receive message tag (integer)
22 comm - communicator (handle)
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26 buf - initial address of send and receive buffer (choice)
27 status - status object (Status)
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31 To dispell a common misconception: src and dest do not have to be the
32 same. Additionally, a common mistake when using this function is to
33 mismatch the tags with the source and destination ranks, which can
34 result in deadlock.
35 This function is guaranteed not to deadlock in situations where pairs
37 of blocking sends and receives may deadlock. For example, the follow‐
38 ing code may deadlock if all ranks in MPI_COMM_WORLD execute it simul‐
39 taneously
40 int rank, size, to, from;
42 MPI_Comm_rank(MPI_COMM_WORLD, &rank);
43 MPI_Comm_size(MPI_COMM_WORLD, &size);
44 to = (rank + 1) % size;
45 from = (rank + size - 1) % size;
46 MPI_Send(send_buffer, ..., to, tag, MPI_COMM_WORLD);
47 MPI_Recv(recv_buffer, ..., from, tag, MPI_COMM_WORLD);
48 If even one rank's MPI_Send blocks and never completes, the entire
51 operation may deadlock. One alternative is to use MPI_Sendrecv in this
52 situation because it is guaranteed not to deadlock.
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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.
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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_TAG
100 - Invalid tag argument. Tags must be non-negative; tags in a
101 receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also
102 be MPI_ANY_TAG . The largest tag value is available through the
103 the attribute MPI_TAG_UB .
104 MPI_ERR_RANK
106 - Invalid source or destination rank. Ranks must be between
107 zero and the size of the communicator minus one; ranks in a
108 receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also
109 be MPI_ANY_SOURCE .
110 MPI_ERR_TRUNCATE
112 - Message truncated on receive. The buffer size specified was
113 too small for the received message. This is a recoverable error
114 in the LAM/MPI implementation.
115 MPI_ERR_OTHER
116 - This error is returned when some part of the LAM/MPI implemen‐
117 tation is unable to acquire memory.
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121 MPI_Sendrecv
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125 For more information, please see the official MPI Forum web site, which
126 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
127 ments contain detailed information about each MPI function (most of
128 which is not duplicated in these man pages).
129 http://www.mpi-forum.org/
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135 The LAM Team would like the thank the MPICH Team for the handy program
136 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
137 ing/sowing.tar.gz ), the initial formatting, and some initial text for
138 most of the MPI-1 man pages.
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141 sendrecvrep.c
142LAM/MPI 7.1.2 2/23/2006 MPI_Sendrecv_replace(3)