newGroup = new simgrid::SMPI::Group(newSize);
for (int i = 0 ; i < newSize ; i++) {
newGroup->set_mapping(oldGroup->index(i), i);
newGroup = new simgrid::SMPI::Group(newSize);
for (int i = 0 ; i < newSize ; i++) {
newGroup->set_mapping(oldGroup->index(i), i);