//create leader_communicator
for (i=0; i< leader_group_size;i++)
leaders_group->set_mapping(s4u::Actor::by_pid(leader_list[i]).get(), i);
//create leader_communicator
for (i=0; i< leader_group_size;i++)
leaders_group->set_mapping(s4u::Actor::by_pid(leader_list[i]).get(), i);