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Updated Calculation Order #1019

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merged 4 commits into from
Sep 21, 2018
Merged

Updated Calculation Order #1019

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95556e8
Updated order Calculation
Rampagy Apr 24, 2018
efb28c0
Added semi-implicit euler option
Rampagy May 1, 2018
1500292
Got implicit and standard euler mixed up
Rampagy May 1, 2018
c54dc72
switched default option
Rampagy May 1, 2018
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15 changes: 11 additions & 4 deletions gym/envs/classic_control/cartpole.py
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@ def __init__(self):
self.polemass_length = (self.masspole * self.length)
self.force_mag = 10.0
self.tau = 0.02 # seconds between state updates
self.kinematics_integrator = 'euler'

# Angle at which to fail the episode
self.theta_threshold_radians = 12 * 2 * math.pi / 360
Expand Down Expand Up @@ -60,10 +61,16 @@ def step(self, action):
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
if self.kinematics_integrator == 'euler':
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looks good to me, but I think the if and else blocks need to be swapped. In this context euler is the method when we update position first (using old velocity), then velocity, and semi-implicit euler - when we first update velocity, then position using new velocity

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
else: # semi-implicit euler
x_dot = x_dot + self.tau * xacc
x = x + self.tau * x_dot
theta_dot = theta_dot + self.tau * thetaacc
theta = theta + self.tau * theta_dot
self.state = (x,x_dot,theta,theta_dot)
done = x < -self.x_threshold \
or x > self.x_threshold \
Expand Down