1MPI_Alltoall(3) LAM/MPI MPI_Alltoall(3)
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6 MPI_Alltoall - Sends data from all to all processes
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9 #include <mpi.h>
10 int MPI_Alltoall(void *sbuf, int scount, MPI_Datatype sdtype,
11 void* rbuf, int rcount, MPI_Datatype rdtype,
12 MPI_Comm comm)
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15 sbuf - starting address of send buffer (choice)
16 scount - number of elements to send to each process (integer)
17 sdtype - data type of send buffer elements (handle)
18 rcount - number of elements received from any process (integer)
19 rdtype - data type of receive buffer elements (handle)
20 comm - communicator (handle)
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24 rbuf - address of receive buffer (choice)
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28 The rcount parameter is the value to be expected from each process, not
29 the total that is expected from all processes. The receive buffer rbuf
30 , however, needs to be large enough to hold the data that will be
31 received from all processes, however.
32 For example, scount and sdtype and typically the same as rcount and
34 rdtype .
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39 LAM/MPI does not yet support invoking this function on a communicator
40 that contains ranks that are non-local IMPI procs.
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44 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
45 an additional argument ierr at the end of the argument list. ierr is
46 an integer and has the same meaning as the return value of the routine
47 in C. In Fortran, MPI routines are subroutines, and are invoked with
48 the call statement.
49 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
51 Fortran.
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55 If an error occurs in an MPI function, the current MPI error handler is
56 called to handle it. By default, this error handler aborts the MPI
57 job. The error handler may be changed with MPI_Errhandler_set ; the
58 predefined error handler MPI_ERRORS_RETURN may be used to cause error
59 values to be returned (in C and Fortran; this error handler is less
60 useful in with the C++ MPI bindings. The predefined error handler
61 MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
62 needs to be recovered). Note that MPI does not guarantee that an MPI
63 program can continue past an error.
64 All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
66 value; C routines as the value of the function and Fortran routines in
67 the last argument. The C++ bindings for MPI do not return error val‐
68 ues; instead, error values are communicated by throwing exceptions of
69 type MPI::Exception (but not by default). Exceptions are only thrown
70 if the error value is not MPI::SUCCESS .
71 Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
74 functions will return upon an error, there will be no way to recover
75 what the actual error value was.
76 MPI_ERR_COMM
77 - Invalid communicator. A common error is to use a null commu‐
78 nicator in a call (not even allowed in MPI_Comm_rank ).
79 MPI_ERR_OTHER
80 - A collective implementation was not able to be located at run-
81 time for this communicator.
82 MPI_ERR_OTHER
83 - A communicator that contains some non-local IMPI procs was
84 used for some function which has not yet had the IMPI extensions
85 implemented yet. For example, most collectives on IMPI communi‐
86 cators have not been implemented yet.
87 MPI_ERR_COUNT
88 - Invalid count argument. Count arguments must be non-negative;
89 a count of zero is often valid.
90 MPI_ERR_TYPE
91 - Invalid datatype argument. May be an uncommitted MPI_Datatype
92 (see MPI_Type_commit ).
93 MPI_ERR_BUFFER
94 - Invalid buffer pointer. Usually a null buffer where one is
95 not valid.
96
99 For more information, please see the official MPI Forum web site, which
100 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
101 ments contain detailed information about each MPI function (most of
102 which is not duplicated in these man pages).
103 http://www.mpi-forum.org/
105
109 The LAM Team would like the thank the MPICH Team for the handy program
110 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
111 ing/sowing.tar.gz ), the initial formatting, and some initial text for
112 most of the MPI-1 man pages.
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115 alltoall.c
116LAM/MPI 7.1.2 2/23/2006 MPI_Alltoall(3)