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++ functions 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