MPI_Group_union(3) Open MPI MPI_Group_union(3)
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
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_GROUP_UNION(GROUP1, GROUP2, NEWGROUP, IERROR)
INTEGER GROUP1, GROUP2, NEWGROUP, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Group_union(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::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++ 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
4.1.2 Nov 24, 2021 MPI_Group_union(3)
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