1MPI_Comm_size(3) LAM/MPI MPI_Comm_size(3)
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6 MPI_Comm_size - Determines the size of the group associated with a
7 communictor
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10 #include <mpi.h>
11 int MPI_Comm_size(MPI_Comm comm, int *psize)
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14 comm - communicator (handle - must be intracommunicator)
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18 psize - number of processes in the group of comm (integer)
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22 MPI_COMM_NULL is not considered a valid argument to this function.
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26 All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
27 an additional argument ierr at the end of the argument list. ierr is
28 an integer and has the same meaning as the return value of the routine
29 in C. In Fortran, MPI routines are subroutines, and are invoked with
30 the call statement.
31 All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
33 Fortran.
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37 If an error occurs in an MPI function, the current MPI error handler is
38 called to handle it. By default, this error handler aborts the MPI
39 job. The error handler may be changed with MPI_Errhandler_set ; the
40 predefined error handler MPI_ERRORS_RETURN may be used to cause error
41 values to be returned (in C and Fortran; this error handler is less
42 useful in with the C++ MPI bindings. The predefined error handler
43 MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
44 needs to be recovered). Note that MPI does not guarantee that an MPI
45 program can continue past an error.
46 All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
48 value; C routines as the value of the function and Fortran routines in
49 the last argument. The C++ bindings for MPI do not return error val‐
50 ues; instead, error values are communicated by throwing exceptions of
51 type MPI::Exception (but not by default). Exceptions are only thrown
52 if the error value is not MPI::SUCCESS .
53 Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
56 functions will return upon an error, there will be no way to recover
57 what the actual error value was.
58 MPI_SUCCESS
59 - No error; MPI routine completed successfully.
60 MPI_ERR_COMM
61 - Invalid communicator. A common error is to use a null commu‐
62 nicator in a call (not even allowed in MPI_Comm_rank ).
63 MPI_ERR_ARG
64 - Invalid argument. Some argument is invalid and is not identi‐
65 fied by a specific error class. This is typically a NULL
66 pointer or other such error.
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70 For more information, please see the official MPI Forum web site, which
71 contains the text of both the MPI-1 and MPI-2 standards. These docu‐
72 ments contain detailed information about each MPI function (most of
73 which is not duplicated in these man pages).
74 http://www.mpi-forum.org/
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80 The LAM Team would like the thank the MPICH Team for the handy program
81 to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow‐
82 ing/sowing.tar.gz ), the initial formatting, and some initial text for
83 most of the MPI-1 man pages.
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86 csize.c
87LAM/MPI 7.1.2 2/23/2006 MPI_Comm_size(3)