def twiddle(tol=0.2):
    """Twiddle algorithm implementation according to Lesson 15, quiz 20 of "Artificial Intelligence for Robotics" course"""

    def get_err(p, i=None, p_i=None):
        if i is not None:
            p = deepcopy(p)
            p[i] = p_i
        robot = make_robot()                # robot-class doesn't presented here
        _, _, err = run(robot, p)
        return err

    p = [0.0, 0.0, 0.0]             # PID components
    dp = [1.0, 1.0, 1.0]
    best_err = get_err(p)

    while sum(dp) > tol:
        for i in range(len(p)):
            for change_direction in (1, -1):
                new_p_i = p[i] + change_direction * dp[i]
                err = get_err(p, i, new_p_i)
                if err < best_err:
                    best_err = err
                    p[i] = new_p_i
                    dp[i] *= 1.1
                    break
            else:
                dp[i] *= 0.9

    # p and error values for lesson example
    # p = [2.9331227688652457, 10.326589894591526, 0.49316041639454505]
    # error = 6.48624850687e-16

    return p, best_err