"""
Classic cart-pole system with continuous action implemented by Rich Sutton et al.
Copied from http://incompleteideas.net/sutton/book/code/pole.c
permalink: https://perma.cc/C9ZM-652R
"""
import logging
import gym
from gym import spaces
from gym.utils import seeding
import autograd.numpy as np
logger = logging.getLogger(__name__)
class CartPoleContinuousEnv(gym.Env):
metadata = {
'render.modes': ['human', 'rgb_array'],
'video.frames_per_second' : 50
}
def __init__(self):
self.gravity = 9.8
self.masscart = 1.0
self.masspole = 0.1
self.total_mass = (self.masspole + self.masscart)
self.length = 0.5 # actually half the pole's length
self.polemass_length = (self.masspole * self.length)
self.max_force = 20.0
self.tau = 0.02 # seconds between state updates
# Angle at which to fail the episode
self.theta_threshold_radians = 12 * 2 * np.pi / 360
self.x_threshold = 2.4
# Angle limit set to 2 * theta_threshold_radians so failing observation is still within bounds
high = np.array([
self.x_threshold * 2,
np.finfo(np.float32).max,
self.theta_threshold_radians * 2,
np.finfo(np.float32).max])
self.action_space = spaces.Box(low=-self.max_force, high=self.max_force, shape=(1,))
self.observation_space = spaces.Box(-high, high)
self._seed()
self.viewer = None
self.state = None
self.steps_beyond_done = None
def _seed(self, seed=None):
self.np_random, seed = seeding.np_random(seed)
return [seed]
def _state_eq(self, st, u):
x, x_dot, theta, theta_dot = st
force = u[0]
costheta = np.cos(theta)
sintheta = np.sin(theta)
temp = (force + self.polemass_length * theta_dot * theta_dot * sintheta) / self.total_mass
thetaacc = (self.gravity * sintheta - costheta* temp) / (self.length * (4.0/3.0 - self.masspole * costheta * costheta / self.total_mass))
xacc = temp - self.polemass_length * thetaacc * costheta / self.total_mass
x = x + self.tau * x_dot
x_dot = x_dot + self.tau * xacc
theta = theta + self.tau * theta_dot
theta_dot = theta_dot + self.tau * thetaacc
return np.array([x, x_dot, theta, theta_dot])
def _step(self, action):
assert self.action_space.contains(action), "%r (%s) invalid"%(action, type(action))
state = self.state
self.state = self._state_eq(state, action)
x, x_dot, theta, theta_dot = self.state
done = x < -self.x_threshold \
or x > self.x_threshold \
or theta < -self.theta_threshold_radians \
or theta > self.theta_threshold_radians
done = bool(done)
if not done:
reward = 1.0
elif self.steps_beyond_done is None:
# Pole just fell!
self.steps_beyond_done = 0
reward = 1.0
else:
if self.steps_beyond_done == 0:
logger.warning("You are calling 'step()' even though this environment has already returned done = True. You should always call 'reset()' once you receive 'done = True' -- any further steps are undefined behavior.")
self.steps_beyond_done += 1
reward = 0.0
return self.state, reward, done, {}
def _reset(self):
self.state = np.array([0.0, 0.0, 0.5 * np.pi, 0.0])
self.steps_beyond_done = None
return np.array(self.state)
def _render(self, mode='human', close=False):
if close:
if self.viewer is not None:
self.viewer.close()
self.viewer = None
return
screen_width = 600
screen_height = 400
world_width = self.x_threshold*2
scale = screen_width/world_width
carty = 100 # TOP OF CART
polewidth = 10.0
polelen = scale * 1.0
cartwidth = 50.0
cartheight = 30.0
if self.viewer is None:
from gym.envs.classic_control import rendering
self.viewer = rendering.Viewer(screen_width, screen_height)
l,r,t,b = -cartwidth/2, cartwidth/2, cartheight/2, -cartheight/2
axleoffset =cartheight/4.0
cart = rendering.FilledPolygon([(l,b), (l,t), (r,t), (r,b)])
self.carttrans = rendering.Transform()
cart.add_attr(self.carttrans)
self.viewer.add_geom(cart)
l,r,t,b = -polewidth/2,polewidth/2,polelen-polewidth/2,-polewidth/2
pole = rendering.FilledPolygon([(l,b), (l,t), (r,t), (r,b)])
pole.set_color(.8,.6,.4)
self.poletrans = rendering.Transform(translation=(0, axleoffset))
pole.add_attr(self.poletrans)
pole.add_attr(self.carttrans)
self.viewer.add_geom(pole)
self.axle = rendering.make_circle(polewidth/2)
self.axle.add_attr(self.poletrans)
self.axle.add_attr(self.carttrans)
self.axle.set_color(.5,.5,.8)
self.viewer.add_geom(self.axle)
self.track = rendering.Line((0,carty), (screen_width,carty))
self.track.set_color(0,0,0)
self.viewer.add_geom(self.track)
if self.state is None: return None
x = self.state
cartx = x[0]*scale+screen_width/2.0 # MIDDLE OF CART
self.carttrans.set_translation(cartx, carty)
self.poletrans.set_rotation(-x[2])
return self.viewer.render(return_rgb_array = mode=='rgb_array')
