def trigger_reordering(bdd):
    """Add several nodes to the manager.

    Dynamic reordering is triggered when the total number
    of nodes that are in the manager reaches a certain threshold.
    We add nodes in order to reach that that threshold,
    and thus trigger reordering.

    To witness the reordering happen,
    look at the logging messages.
    """
    nodes = list()
    for i in range(25):
        expr = ('(x{i1} /\\ x{i2}) \\/ (x{i3} /\\ x{i4}) \\/ (x{i5} /\\ x{i6})'
            .format(i1=i, i2=i + 6, i3=i + 7, i4=i + 8, i5=i + 9, i6=i + 10))
        u = bdd.add_expr(expr)
        nodes.append(u)
    return nodes
