NAME

       MPI_Group_intersection  - Produces a group at the intersection of two existing groups.

SYNTAX

C Syntax

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

Fortran Syntax

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_GROUP_INTERSECTION(GROUP1, GROUP2, NEWGROUP, IERROR)
            INTEGER   GROUP1, GROUP2, NEWGROUP, IERROR

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Group_intersection(group1, group2, newgroup, ierror)
            TYPE(MPI_Group), INTENT(IN) :: group1, group2
            TYPE(MPI_Group), INTENT(OUT) :: newgroup
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax

       #include <mpi.h>
       static Group Group::Intersect(const Group& group1, const Group& group2)

INPUT PARAMETERS

       group1    First group (handle).

       group2    Second group (handle).

OUTPUT PARAMETERS

       newgroup  Intersection 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

4.1.6                                             Sep 30, 2023                         MPI_Group_intersection(3)