1MPI_Comm_compare(3) LAM/MPI MPI_Comm_compare(3)
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6 MPI_Comm_compare - Compares two communicators
7
9 #include <mpi.h>
10 int MPI_Comm_compare(MPI_Comm c1, MPI_Comm c2,
11 int *result)
12
14 c1 - comm1 (handle)
15 c2 - comm2 (handle)
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19 result - integer which is MPI_IDENT if the contexts and groups are the
20 same, MPI_CONGRUENT if different contexts but identical groups,
21 MPI_SIMILAR if different contexts but similar groups, and
22 MPI_UNEQUAL otherwise
23
26 It is an error to use MPI_COMM_NULL as one of the arguments to
27 MPI_Comm_compare . The relevant sections of the MPI standard are
28 (2.4.1 Opaque Objects) A null handle argument is an erroneous IN argu‐
30 ment in MPI calls, unless an exception is explicitly stated in the text
31 that defines the function.
32 (5.4.1. Communicator Accessors) <no text in MPI_COMM_COMPARE allowing a
34 null handle>
35
38 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
39 an additional argument ierr at the end of the argument list. ierr is
40 an integer and has the same meaning as the return value of the routine
41 in C. In Fortran, MPI routines are subroutines, and are invoked with
42 the call statement.
43 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
45 Fortran.
46
49 If an error occurs in an MPI function, the current MPI error handler is
50 called to handle it. By default, this error handler aborts the MPI
51 job. The error handler may be changed with MPI_Errhandler_set ; the
52 predefined error handler MPI_ERRORS_RETURN may be used to cause error
53 values to be returned (in C and Fortran; this error handler is less
54 useful in with the C++ MPI bindings. The predefined error handler
55 MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
56 needs to be recovered). Note that MPI does not guarantee that an MPI
57 program can continue past an error.
58 All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
60 value; C routines as the value of the function and Fortran routines in
61 the last argument. The C++ bindings for MPI do not return error val‐
62 ues; instead, error values are communicated by throwing exceptions of
63 type MPI::Exception (but not by default). Exceptions are only thrown
64 if the error value is not MPI::SUCCESS .
65 Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
68 functions will return upon an error, there will be no way to recover
69 what the actual error value was.
70 MPI_SUCCESS
71 - No error; MPI routine completed successfully.
72 MPI_ERR_COMM
73 - Invalid communicator. A common error is to use a null commu‐
74 nicator in a call (not even allowed in MPI_Comm_rank ).
75 MPI_ERR_ARG
76 - Invalid argument. Some argument is invalid and is not identi‐
77 fied by a specific error class. This is typically a NULL
78 pointer or other such error.
79
82 For more information, please see the official MPI Forum web site, which
83 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
84 ments contain detailed information about each MPI function (most of
85 which is not duplicated in these man pages).
86 http://www.mpi-forum.org/
88
92 The LAM Team would like the thank the MPICH Team for the handy program
93 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
94 ing/sowing.tar.gz ), the initial formatting, and some initial text for
95 most of the MPI-1 man pages.
96
98 ccmp.c
99LAM/MPI 7.1.2 2/23/2006 MPI_Comm_compare(3)