1MPI_Intercomm_create(3) LAM/MPI MPI_Intercomm_create(3)
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6 MPI_Intercomm_create - Creates an intercommuncator from two intracom‐
7 municators
8
10 #include <mpi.h>
11 int MPI_Intercomm_create(MPI_Comm lcomm, int lleader,
12 MPI_Comm pcomm, int pleader, int tag,
13 MPI_Comm *newcomm)
14
16 lcomm - Local (intra)communicator
17 lleader
18 - Rank in local_comm of leader (often 0)
19 pcomm - Remote communicator
20 pleader
21 - Rank in peer_comm of remote leader (often 0)
22 tag - Message tag to use in constructing intercommunicator; if mul‐
23 tiple MPI_Intercomm_creates are being made, they should use dif‐
24 ferent tags (more precisely, ensure that the local and remote
25 leaders are using different tags for each MPI_intercomm_create
26 ).
27
30 newcomm
31 - Created intercommunicator
32
35 The MPI 1.1 Standard contains two mutually exclusive comments on the
36 input intracommunicators. One says that their repective groups must be
37 disjoint; the other that the leaders can be the same process. After
38 some discussion by the MPI Forum, it has been decided that the groups
39 must be disjoint. Note that the reason given for this in the standard
40 is not the reason for this choice; rather, the other operations on
41 intercommunicators (like MPI_Intercomm_merge ) do not make sense if the
42 groups are not disjoint.
43
46 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
47 an additional argument ierr at the end of the argument list. ierr is
48 an integer and has the same meaning as the return value of the routine
49 in C. In Fortran, MPI routines are subroutines, and are invoked with
50 the call statement.
51 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
53 Fortran.
54
57 If an error occurs in an MPI function, the current MPI error handler is
58 called to handle it. By default, this error handler aborts the MPI
59 job. The error handler may be changed with MPI_Errhandler_set ; the
60 predefined error handler MPI_ERRORS_RETURN may be used to cause error
61 values to be returned (in C and Fortran; this error handler is less
62 useful in with the C++ MPI bindings. The predefined error handler
63 MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
64 needs to be recovered). Note that MPI does not guarantee that an MPI
65 program can continue past an error.
66 All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
68 value; C routines as the value of the function and Fortran routines in
69 the last argument. The C++ bindings for MPI do not return error val‐
70 ues; instead, error values are communicated by throwing exceptions of
71 type MPI::Exception (but not by default). Exceptions are only thrown
72 if the error value is not MPI::SUCCESS .
73 Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
76 functions will return upon an error, there will be no way to recover
77 what the actual error value was.
78 MPI_SUCCESS
79 - No error; MPI routine completed successfully.
80 MPI_ERR_COMM
81 - Invalid communicator. A common error is to use a null commu‐
82 nicator in a call (not even allowed in MPI_Comm_rank ).
83 MPI_ERR_TAG
84 - Invalid tag argument. Tags must be non-negative; tags in a
85 receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also
86 be MPI_ANY_TAG . The largest tag value is available through the
87 the attribute MPI_TAG_UB .
88 MPI_ERR_ARG
90 - Invalid argument. Some argument is invalid and is not identi‐
91 fied by a specific error class. This is typically a NULL
92 pointer or other such error.
93 MPI_ERR_OTHER
94 - This error is returned when some part of the LAM/MPI implemen‐
95 tation is unable to acquire memory.
96 MPI_ERR_RANK
97 - Invalid source or destination rank. Ranks must be between
98 zero and the size of the communicator minus one; ranks in a
99 receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also
100 be MPI_ANY_SOURCE .
101
105 MPI_Intercomm_merge, MPI_Comm_free, MPI_Comm_remote_group,
106 MPI_Comm_remote_size
107
110 For more information, please see the official MPI Forum web site, which
111 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
112 ments contain detailed information about each MPI function (most of
113 which is not duplicated in these man pages).
114 http://www.mpi-forum.org/
116
120 The LAM Team would like the thank the MPICH Team for the handy program
121 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
122 ing/sowing.tar.gz ), the initial formatting, and some initial text for
123 most of the MPI-1 man pages.
124
126 iccreate.c
127LAM/MPI 7.1.2 2/23/2006 MPI_Intercomm_create(3)