MPI_Group_difference(3OpenMPI)											    MPI_Group_difference(3OpenMPI)

NAME

       MPI_Group_difference  - Makes a group from the difference of two groups.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Group_difference(MPI_Group group1, MPI_Group group2,
	    MPI_Group *newgroup)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_GROUP_DIFFERENCE(GROUP1, GROUP2, NEWGROUP, IERROR)
	    INTEGER   GROUP1, GROUP2, NEWGROUP, IERROR

C++ Syntax
       #include <mpi.h>
       static Group Group::Difference(const Group& group1, const Group& group2)

INPUT PARAMETERS

       group1	 First group (handle).

       group2	 Second group (handle).

OUTPUT PARAMETERS

       newgroup  Difference group (handle).

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       The set-like operations are defined as follows:

	 o    union -- All elements of the first group (group1), followed by all elements of second group (group2) that are not in the first group

	 o    intersect -- all elements of the first group that are also in the second group, ordered as in first group

	 o    difference -- all elements of the first group that are not in the second group, ordered as in the first group

       Note that for these operations the order of processes in the output group is determined primarily by order in the first group (if possible)
       and then, if necessary, by order in the second group. Neither union nor intersection are commutative, but both are associative.

       The new group can be empty, that is, equal to MPI_GROUP_EMPTY.

ERRORS

       Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func-
       tions  do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except  for
       I/O  function  errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be
       used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

SEE ALSO

       MPI_Group_free

Open MPI 1.2							  September 2006				    MPI_Group_difference(3OpenMPI)