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MPI_Group_union(3OpenMPI)                                                          MPI_Group_union(3OpenMPI)



NAME
       MPI_Group_union  - Produces a group by combining two groups.


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


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


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


INPUT PARAMETERS
       group1    First group (handle).

       group2    Second group (handle).


OUTPUT PARAMETERS
       newgroup  Union 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) not in first.

         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




Open MPI 1.2                                   September 2006                      MPI_Group_union(3OpenMPI)