def heuristic()

in gym/gym/envs/box2d/lunar_lander.py [0:0]

• 19 lines of code
• 10 McCabe index (conditional complexity)

def heuristic(env, s):
    # Heuristic for:
    # 1. Testing. 
    # 2. Demonstration rollout.
    angle_targ = s[0]*0.5 + s[2]*1.0         # angle should point towards center (s[0] is horizontal coordinate, s[2] hor speed)
    if angle_targ >  0.4: angle_targ =  0.4  # more than 0.4 radians (22 degrees) is bad
    if angle_targ < -0.4: angle_targ = -0.4
    hover_targ = 0.55*np.abs(s[0])           # target y should be proporional to horizontal offset

    # PID controller: s[4] angle, s[5] angularSpeed
    angle_todo = (angle_targ - s[4])*0.5 - (s[5])*1.0
    #print("angle_targ=%0.2f, angle_todo=%0.2f" % (angle_targ, angle_todo))

    # PID controller: s[1] vertical coordinate s[3] vertical speed
    hover_todo = (hover_targ - s[1])*0.5 - (s[3])*0.5
    #print("hover_targ=%0.2f, hover_todo=%0.2f" % (hover_targ, hover_todo))

    if s[6] or s[7]: # legs have contact
        angle_todo = 0
        hover_todo = -(s[3])*0.5  # override to reduce fall speed, that's all we need after contact

    if env.continuous:
        a = np.array( [hover_todo*20 - 1, -angle_todo*20] )
        a = np.clip(a, -1, +1)
    else:
        a = 0
        if hover_todo > np.abs(angle_todo) and hover_todo > 0.05: a = 2
        elif angle_todo < -0.05: a = 3
        elif angle_todo > +0.05: a = 1
    return a