1MPI_Gather(3) LAM/MPI MPI_Gather(3)
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6 MPI_Gather - Gathers together values from a group of processes
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9 #include <mpi.h>
10 int MPI_Gather(void *sbuf, int scount, MPI_Datatype sdtype,
11 void *rbuf, int rcount, MPI_Datatype rdtype,
12 int root, MPI_Comm comm)
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15 sbuf - starting address of send buffer (choice)
16 scount - number of elements in send buffer (integer)
17 sdtype - data type of send buffer elements (handle)
18 rcount - number of elements for any single receive (integer, signifi‐
19 cant only at root)
20 rdtype - data type of recv buffer elements (significant only at root)
21 (handle)
22 root - rank of receiving process (integer)
23 comm - communicator (handle)
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27 rbuf - address of receive buffer (choice, significant only at root )
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31 LAM/MPI does not yet support invoking this function on a communicator
32 that contains ranks that are non-local IMPI procs.
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36 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
37 an additional argument ierr at the end of the argument list. ierr is
38 an integer and has the same meaning as the return value of the routine
39 in C. In Fortran, MPI routines are subroutines, and are invoked with
40 the call statement.
41 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
43 Fortran.
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47 If an error occurs in an MPI function, the current MPI error handler is
48 called to handle it. By default, this error handler aborts the MPI
49 job. The error handler may be changed with MPI_Errhandler_set ; the
50 predefined error handler MPI_ERRORS_RETURN may be used to cause error
51 values to be returned (in C and Fortran; this error handler is less
52 useful in with the C++ MPI bindings. The predefined error handler
53 MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
54 needs to be recovered). Note that MPI does not guarantee that an MPI
55 program can continue past an error.
56 All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
58 value; C routines as the value of the function and Fortran routines in
59 the last argument. The C++ bindings for MPI do not return error val‐
60 ues; instead, error values are communicated by throwing exceptions of
61 type MPI::Exception (but not by default). Exceptions are only thrown
62 if the error value is not MPI::SUCCESS .
63 Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
66 functions will return upon an error, there will be no way to recover
67 what the actual error value was.
68 MPI_SUCCESS
69 - No error; MPI routine completed successfully.
70 MPI_ERR_COMM
71 - Invalid communicator. A common error is to use a null commu‐
72 nicator in a call (not even allowed in MPI_Comm_rank ).
73 MPI_ERR_OTHER
74 - A collective implementation was not able to be located at run-
75 time for this communicator.
76 MPI_ERR_COUNT
77 - Invalid count argument. Count arguments must be non-negative;
78 a count of zero is often valid.
79 MPI_ERR_TYPE
80 - Invalid datatype argument. May be an uncommitted MPI_Datatype
81 (see MPI_Type_commit ).
82 MPI_ERR_BUFFER
83 - Invalid buffer pointer. Usually a null buffer where one is
84 not valid.
85 MPI_ERR_ROOT
86 - Invalid root. The root must be specified as a rank in the
87 communicator. Ranks must be between zero and the size of the
88 communicator minus one.
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92 For more information, please see the official MPI Forum web site, which
93 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
94 ments contain detailed information about each MPI function (most of
95 which is not duplicated in these man pages).
96 http://www.mpi-forum.org/
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102 The LAM Team would like the thank the MPICH Team for the handy program
103 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
104 ing/sowing.tar.gz ), the initial formatting, and some initial text for
105 most of the MPI-1 man pages.
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108 gather.c
109LAM/MPI 7.1.2 2/23/2006 MPI_Gather(3)