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NAME

MPI_Group_compare - Compares two groups

SYNOPSIS

#include <mpi.h> int MPI_Group_compare(MPI_Group g1 , MPI_Group g2 , int *result );

#include <pmpi.h> int PMPI_Group_compare(MPI_Group g1 , MPI_Group g2 , int *result );

#include <mpi.h> static int MPI::Group::Compare(const MPI::Group &g1 , const MPI::Group &g2 );

INCLUDE 'mpif.h' MPI_GROUP_COMPARE(g1 , g2 , result , ierr ) INTEGER g1 , g2 , result , ierr

INPUT PARAMETERS

g1 - group (handle)

g2 - group (handle)

OUTPUT PARAMETER

result - the result of the comparison (integer).

DESCRIPTION

The MPI_Group_compare() function is used to compare two groups g1 and g2 . If the two groups are identical, then MPI_IDENT is returned in result . If they contain the same processes, but with a different order of ranks, then MPI_SIMILAR is returned. Otherwise MPI_UNEQUAL is returned in result .

In the C++ version of this function, the result is passed as the return value.

Note that the groups must be valid (not MPI_GROUP_NULL). PMPI_Group_compare() is the profiling version of this function.

ERRORS

All MPI routines except for MPI_Wtime and MPI_Wtick return an error code. The the current MPI error handler is invoked if the return value is not MPI_SUCCESS. The default error handler aborts, but this may be changed with by using the MPI_Errhandler_set() function. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead. Note that MPI does not guarentee that an MPI program can continue past an error. In this implementation, all errors except MPI_ERR_INTERN or MPI_ERR_OTHER should always be recoverable.

In C, the error code is passed as the return value. In FORTRAN, all functions have an parameter ierr which returns the error code. MPI C++ functions do not directly return an error code. However, C++ users may want to use the MPI::ERRORS_THROW_EXCEPTIONS handler. This will throw an MPI::Exception with the corresponding error code. To prevent exceptions from being raised from within C and Fortran code, they will see all error return values as MPI_ERR_PENDING when this handler is chosen. In this implementation, call MPI::throw_exception() to throw the correct exception if this occurs.

MPI_SUCCESS - No error;

MPI_ERR_PENDING - Pending exception;

MPI_ERR_GROUP - Invalid group;

MPI_ERR_ARG - Invalid output pointer.

SEE ALSO

MPI_Comm_compare (3) MPI_Group_rank (3) MPI_Group_size (3) MPI_Group_free (3)

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