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import numpy as np
from gym import utils
from gym.envs.mujoco import mujoco_env
class AntEnv(mujoco_env.MujocoEnv, utils.EzPickle):
def __init__(self):
mujoco_env.MujocoEnv.__init__(self, 'ant.xml', 5)
utils.EzPickle.__init__(self)
def step(self, a):
xposbefore = self.get_body_com("torso")[0]
self.do_simulation(a, self.frame_skip)
xposafter = self.get_body_com("torso")[0]
forward_reward = (xposafter - xposbefore)/self.dt
ctrl_cost = .5 * np.square(a).sum()
contact_cost = 0.5 * 1e-3 * np.sum(
np.square(np.clip(self.sim.data.cfrc_ext, -1, 1)))
survive_reward = 1.0
reward = forward_reward - ctrl_cost - contact_cost + survive_reward
state = self.state_vector()
notdone = np.isfinite(state).all() \
and state[2] >= 0.2 and state[2] <= 1.0
done = not notdone
ob = self._get_obs()
return ob, reward, done, dict(
reward_forward=forward_reward,
reward_ctrl=-ctrl_cost,
reward_contact=-contact_cost,
reward_survive=survive_reward)
def _get_obs(self):
return np.concatenate([
self.sim.data.qpos.flat[2:],
self.sim.data.qvel.flat,
np.clip(self.sim.data.cfrc_ext, -1, 1).flat,
])
def reset_model(self):
qpos = self.init_qpos + self.np_random.uniform(size=self.model.nq, low=-.1, high=.1)
qvel = self.init_qvel + self.np_random.randn(self.model.nv) * .1
self.set_state(qpos, qvel)
return self._get_obs()
def viewer_setup(self):
self.viewer.cam.distance = self.model.stat.extent * 0.5