1MPI_Alltoallw(3) LAM/MPI MPI_Alltoallw(3)
2
6 MPI_Alltoallw - Sends data from all to all processes, with a displace‐
7 ment
8
10 #include <mpi.h>
11 int MPI_Alltoallw(void *sbuf, int *scounts, int *sdisps,
12 MPI_Datatype *sdtypes, void *rbuf, int *rcounts,
13 int *rdisps, MPI_Datatype *rdtypes,
14 MPI_Comm comm)
15
17 sbuf - starting address of send buffer (choice)
18 scounts
19 - integer array equal to the group size specifying the number of
20 elements to send to each processor
21 sdisps - integer array (of length group size). Entry j specifies the
22 displacement (relative to sendbuf from which to take the outgo‐
23 ing data destined for process j
24 sdtype - data type of send buffer elements (handle)
26 rcounts
27 - integer array equal to the group size specifying the maximum
28 number of elements that can be received from each processor
29 rdisps - integer array (of length group size). Entry i specifies the
30 displacement (relative to recvbuf at which to place the incom‐
31 ing data from process i
32 rdtypes
34 - data types of receive buffer elements (handle)
35 comm - communicator (handle)
36
39 rbuf - address of receive buffer (choice)
40
43 The receive buffer rbuf needs to be large enough to hold the data that
44 will be received from all processes.
45
48 LAM/MPI does not yet support invoking this function on a communicator
49 that contains ranks that are non-local IMPI procs.
50
53 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
54 an additional argument ierr at the end of the argument list. ierr is
55 an integer and has the same meaning as the return value of the routine
56 in C. In Fortran, MPI routines are subroutines, and are invoked with
57 the call statement.
58 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
60 Fortran.
61
64 If an error occurs in an MPI function, the current MPI error handler is
65 called to handle it. By default, this error handler aborts the MPI
66 job. The error handler may be changed with MPI_Errhandler_set ; the
67 predefined error handler MPI_ERRORS_RETURN may be used to cause error
68 values to be returned (in C and Fortran; this error handler is less
69 useful in with the C++ MPI bindings. The predefined error handler
70 MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
71 needs to be recovered). Note that MPI does not guarantee that an MPI
72 program can continue past an error.
73 All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
75 value; C routines as the value of the function and Fortran routines in
76 the last argument. The C++ bindings for MPI do not return error val‐
77 ues; instead, error values are communicated by throwing exceptions of
78 type MPI::Exception (but not by default). Exceptions are only thrown
79 if the error value is not MPI::SUCCESS .
80 Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
83 functions will return upon an error, there will be no way to recover
84 what the actual error value was.
85 MPI_ERR_COMM
86 - Invalid communicator. A common error is to use a null commu‐
87 nicator in a call (not even allowed in MPI_Comm_rank ).
88 MPI_ERR_OTHER
89 - A collective implementation was not able to be located at run-
90 time for this communicator.
91 MPI_ERR_OTHER
92 - A communicator that contains some non-local IMPI procs was
93 used for some function which has not yet had the IMPI extensions
94 implemented yet. For example, most collectives on IMPI communi‐
95 cators have not been implemented yet.
96 MPI_ERR_COUNT
97 - Invalid count argument. Count arguments must be non-negative;
98 a count of zero is often valid.
99 MPI_ERR_TYPE
100 - Invalid datatype argument. May be an uncommitted MPI_Datatype
101 (see MPI_Type_commit ).
102 MPI_ERR_BUFFER
103 - Invalid buffer pointer. Usually a null buffer where one is
104 not valid.
105
108 For more information, please see the official MPI Forum web site, which
109 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
110 ments contain detailed information about each MPI function (most of
111 which is not duplicated in these man pages).
112 http://www.mpi-forum.org/
114
118 The LAM Team would like the thank the MPICH Team for the handy program
119 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
120 ing/sowing.tar.gz ), the initial formatting, and some initial text for
121 most of the MPI-1 man pages.
122
124 alltoallw.c
125LAM/MPI 7.1.2 2/23/2006 MPI_Alltoallw(3)