def create_comms_and_role_node(comm, node_comm, node_root):
    """Approach: each node root builds, everyone waits on their node group."""
    copy_comm = None
    wait_comm = node_comm
    if node_comm.rank == 0:
        assert comm.rank == node_root
        role = 'builder'
    else:
        assert comm.rank != node_root
        role = 'waiter'
    return copy_comm, wait_comm, role
