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"""
http://incompleteideas.net/sutton/MountainCar/MountainCar1.cp
permalink: https://perma.cc/6Z2N-PFWC
"""
import math
import numpy as np
import gym
from gym import spaces
from gym.utils import seeding
class MountainCarEnv(gym.Env):
metadata = {
'render.modes': ['human', 'rgb_array'],
'video.frames_per_second': 30
}
def __init__(self):
self.min_position = -1.2
self.max_position = 0.6
self.max_speed = 0.07
self.goal_position = 0.5
self.low = np.array([self.min_position, -self.max_speed])
self.high = np.array([self.max_position, self.max_speed])
self.viewer = None
self.action_space = spaces.Discrete(3)
self.observation_space = spaces.Box(self.low, self.high, dtype=np.float32)
self.seed()
self.reset()
def seed(self, seed=None):
self.np_random, seed = seeding.np_random(seed)
return [seed]
def step(self, action):
assert self.action_space.contains(action), "%r (%s) invalid" % (action, type(action))
position, velocity = self.state
velocity += (action-1)*0.001 + math.cos(3*position)*(-0.0025)
velocity = np.clip(velocity, -self.max_speed, self.max_speed)
position += velocity
position = np.clip(position, self.min_position, self.max_position)
if (position==self.min_position and velocity<0): velocity = 0
done = bool(position >= self.goal_position)
reward = -1.0
self.state = (position, velocity)
return np.array(self.state), reward, done, {}
def reset(self):
self.state = np.array([self.np_random.uniform(low=-0.6, high=-0.4), 0])
return np.array(self.state)
def _height(self, xs):
return np.sin(3 * xs)*.45+.55
def render(self, mode='human'):
screen_width = 600
screen_height = 400
world_width = self.max_position - self.min_position
scale = screen_width/world_width
carwidth=40
carheight=20
if self.viewer is None:
from gym.envs.classic_control import rendering
self.viewer = rendering.Viewer(screen_width, screen_height)
xs = np.linspace(self.min_position, self.max_position, 100)
ys = self._height(xs)
xys = list(zip((xs-self.min_position)*scale, ys*scale))
self.track = rendering.make_polyline(xys)
self.track.set_linewidth(4)
self.viewer.add_geom(self.track)
clearance = 10
l,r,t,b = -carwidth/2, carwidth/2, carheight, 0
car = rendering.FilledPolygon([(l,b), (l,t), (r,t), (r,b)])
car.add_attr(rendering.Transform(translation=(0, clearance)))
self.cartrans = rendering.Transform()
car.add_attr(self.cartrans)
self.viewer.add_geom(car)
frontwheel = rendering.make_circle(carheight/2.5)
frontwheel.set_color(.5, .5, .5)
frontwheel.add_attr(rendering.Transform(translation=(carwidth/4,clearance)))
frontwheel.add_attr(self.cartrans)
self.viewer.add_geom(frontwheel)
backwheel = rendering.make_circle(carheight/2.5)
backwheel.add_attr(rendering.Transform(translation=(-carwidth/4,clearance)))
backwheel.add_attr(self.cartrans)
backwheel.set_color(.5, .5, .5)
self.viewer.add_geom(backwheel)
flagx = (self.goal_position-self.min_position)*scale
flagy1 = self._height(self.goal_position)*scale
flagy2 = flagy1 + 50
flagpole = rendering.Line((flagx, flagy1), (flagx, flagy2))
self.viewer.add_geom(flagpole)
flag = rendering.FilledPolygon([(flagx, flagy2), (flagx, flagy2-10), (flagx+25, flagy2-5)])
flag.set_color(.8,.8,0)
self.viewer.add_geom(flag)
pos = self.state[0]
self.cartrans.set_translation((pos-self.min_position)*scale, self._height(pos)*scale)
self.cartrans.set_rotation(math.cos(3 * pos))
return self.viewer.render(return_rgb_array = mode=='rgb_array')
def close(self):
if self.viewer:
self.viewer.close()
self.viewer = None