17.2.196. MPI_Group_union

MPI_Group_union - Produces a group by combining two groups.

17.2.196.1. SYNTAX

17.2.196.1.1. C Syntax

#include <mpi.h>

int MPI_Group_union(MPI_Group group1, MPI_Group group2,
     MPI_Group *newgroup)

17.2.196.1.2. Fortran Syntax

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

17.2.196.1.3. 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

17.2.196.2. INPUT PARAMETERS

  • group1: First group (handle).

  • group2: Second group (handle).

17.2.196.3. OUTPUT PARAMETERS

  • newgroup: Union group (handle).

  • IERROR: Fortran only: Error status (integer).

17.2.196.4. 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.

17.2.196.5. ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

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