NAME

       MPI_Comm_compare -  Compares two communicators

SYNOPSIS

       #include <mpi.h>
       int MPI_Comm_compare(MPI_Comm c1, MPI_Comm c2,
                           int *result)

INPUT PARAMETERS

       c1     - comm1 (handle)
       c2     - comm2 (handle)

OUTPUT PARAMETER

       result -  integer  which is MPI_IDENT if the contexts and groups are the same, MPI_CONGRUENT if different
              contexts but  identical  groups,  MPI_SIMILAR  if  different  contexts  but  similar  groups,  and
              MPI_UNEQUAL otherwise

USING 'MPI_COMM_NULL' WITH 'MPI_COMM_COMPARE'

       It  is an error to use MPI_COMM_NULL as one of the arguments to MPI_Comm_compare .  The relevant sections
       of the MPI standard are

       (2.4.1 Opaque Objects) A null handle argument is an  erroneous  IN  argument  in  MPI  calls,  unless  an
       exception is explicitly stated in the text that defines the function.

       (5.4.1. Communicator Accessors) <no text in MPI_COMM_COMPARE allowing a null handle>

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the
       end of the argument list.  ierr is an integer and has the same meaning as the return value of the routine
       in C.  In Fortran, MPI routines are subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       If an error occurs in an MPI function, the current MPI error handler is called to handle it.  By default,
       this  error  handler  aborts the MPI job.  The error handler may be changed with MPI_Errhandler_set ; the
       predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be  returned  (in  C  and
       Fortran;  this  error  handler is less useful in with the C++ MPI bindings.  The predefined error handler
       MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value needs to be recovered).  Note  that
       MPI does not guarantee that an MPI program can continue past an error.

       All  MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of the
       function and Fortran routines in the last argument.  The C++ bindings for MPI do not return error values;
       instead, error values are communicated  by  throwing  exceptions  of  type  MPI::Exception  (but  not  by
       default).  Exceptions are only thrown if the error value is not MPI::SUCCESS .

       Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return upon an error,
       there will be no way to recover what the actual error value was.
       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_COMM
              -  Invalid communicator.  A common error is to use a null communicator in a call (not even allowed
              in MPI_Comm_rank ).
       MPI_ERR_ARG
              - Invalid argument.  Some argument is invalid and is not identified by  a  specific  error  class.
              This is typically a NULL pointer or other such error.

MORE INFORMATION

       For  more  information,  please  see the official MPI Forum web site, which contains the text of both the
       MPI-1 and MPI-2 standards.  These documents contain detailed information about each MPI function (most of
       which is not duplicated in these man pages).

       http://www.mpi-forum.org/

ACKNOWLEDGEMENTS

       The LAM Team would like the thank the MPICH Team for the handy program to generate man  pages  ("doctext"
       from  ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz ), the initial formatting, and some initial text for
       most of the MPI-1 man pages.

LOCATION

       ccmp.c

LAM/MPI 7.1.4                                       6/24/2006                                MPI_Comm_compare(3)