17.2.184. MPI_Group_difference

MPI_Group_difference - Makes a group from the difference of two groups.

17.2.184.1. Syntax

17.2.184.1.1. C Syntax

#include <mpi.h>

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

17.2.184.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_GROUP_DIFFERENCE(GROUP1, GROUP2, NEWGROUP, IERROR)
    INTEGER GROUP1, GROUP2, NEWGROUP, IERROR

17.2.184.1.3. Fortran 2008 Syntax

USE mpi_f08

MPI_Group_difference(group1, group2, newgroup, ierror)
    TYPE(MPI_Group), INTENT(IN) :: group1, group2
    TYPE(MPI_Group), INTENT(OUT) :: newgroup
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.184.2. Input Parameters

group1 : First group (handle).
group2 : Second group (handle).

17.2.184.3. Output Parameters

newgroup : Difference group (handle).
IERROR : Fortran only: Error status (integer).

17.2.184.4. Description

The set-like operations are defined as follows:

union – All elements of the first group (group1), followed by all elements of second group (group2) that are not in the first group
intersect – all elements of the first group that are also in the second group, ordered as in first group
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.

17.2.184.5. 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.