1MPI_Bcast(3) LAM/MPI MPI_Bcast(3)
2
6 MPI_Bcast - Broadcasts a message from the process with rank "root" to
7 all other processes of the group.
8
10 #include <mpi.h>
11 int MPI_Bcast(void *buff, int count, MPI_Datatype datatype,
12 int root, MPI_Comm comm)
13
15 buff - starting address of buffer (choice)
16 count - number of entries in buffer (integer)
17 datatype
18 - data type of buffer (handle)
19 root - rank of broadcast root (integer)
20 comm - communicator (handle)
21
24 This function has had the IMPI extensions implemented. It is legal to
25 call this function on IMPI communicators.
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29 For 4 or less ranks, a linear algorithm is used, where rank 0 loops
30 over sending the message to each other rank.
31 If more than 4 ranks are involved, a tree-based algorithm is used to
33 send the messages from rank 0.
34
37 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
38 an additional argument ierr at the end of the argument list. ierr is
39 an integer and has the same meaning as the return value of the routine
40 in C. In Fortran, MPI routines are subroutines, and are invoked with
41 the call statement.
42 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
44 Fortran.
45
48 If an error occurs in an MPI function, the current MPI error handler is
49 called to handle it. By default, this error handler aborts the MPI
50 job. The error handler may be changed with MPI_Errhandler_set ; the
51 predefined error handler MPI_ERRORS_RETURN may be used to cause error
52 values to be returned (in C and Fortran; this error handler is less
53 useful in with the C++ MPI bindings. The predefined error handler
54 MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
55 needs to be recovered). Note that MPI does not guarantee that an MPI
56 program can continue past an error.
57 All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
59 value; C routines as the value of the function and Fortran routines in
60 the last argument. The C++ bindings for MPI do not return error val‐
61 ues; instead, error values are communicated by throwing exceptions of
62 type MPI::Exception (but not by default). Exceptions are only thrown
63 if the error value is not MPI::SUCCESS .
64 Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
67 functions will return upon an error, there will be no way to recover
68 what the actual error value was.
69 MPI_SUCCESS
70 - No error; MPI routine completed successfully.
71 MPI_ERR_COMM
72 - Invalid communicator. A common error is to use a null commu‐
73 nicator in a call (not even allowed in MPI_Comm_rank ).
74 MPI_ERR_OTHER
75 - A collective implementation was not able to be located at run-
76 time for this communicator.
77 MPI_ERR_COUNT
78 - Invalid count argument. Count arguments must be non-negative;
79 a count of zero is often valid.
80 MPI_ERR_TYPE
81 - Invalid datatype argument. May be an uncommitted MPI_Datatype
82 (see MPI_Type_commit ).
83 MPI_ERR_BUFFER
84 - Invalid buffer pointer. Usually a null buffer where one is
85 not valid.
86 MPI_ERR_ROOT
87 - Invalid root. The root must be specified as a rank in the
88 communicator. Ranks must be between zero and the size of the
89 communicator minus one.
90
93 For more information, please see the official MPI Forum web site, which
94 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
95 ments contain detailed information about each MPI function (most of
96 which is not duplicated in these man pages).
97 http://www.mpi-forum.org/
99
103 The LAM Team would like the thank the MPICH Team for the handy program
104 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
105 ing/sowing.tar.gz ), the initial formatting, and some initial text for
106 most of the MPI-1 man pages.
107
109 bcast.c
110LAM/MPI 7.1.2 2/23/2006 MPI_Bcast(3)