import numpy as np
from mushroom_rl.algorithms.policy_search.policy_gradient import PolicyGradient
[docs]class eNAC(PolicyGradient):
"""
Episodic Natural Actor Critic algorithm.
"A Survey on Policy Search for Robotics", Deisenroth M. P., Neumann G.,
Peters J. 2013.
"""
[docs] def __init__(self, mdp_info, policy, optimizer, features=None,
critic_features=None):
"""
Constructor.
Args:
critic_features (Features, None): features used by the critic.
"""
super().__init__(mdp_info, policy, optimizer, features)
self.phi_c = critic_features
self.sum_grad_log = None
self.psi_ext = None
self.sum_grad_log_list = list()
self._add_save_attr(
phi_c='pickle',
sum_grad_log='numpy',
psi_ext='pickle',
sum_grad_log_list='pickle'
)
[docs] def _compute_gradient(self, J):
R = np.array(J)
PSI = np.array(self.sum_grad_log_list)
w_and_v = np.linalg.pinv(PSI).dot(R)
nat_grad = w_and_v[:self.policy.weights_size]
self.sum_grad_log_list = list()
return nat_grad
[docs] def _step_update(self, x, u, r):
self.sum_grad_log += self.df*self.policy.diff_log(x, u)
if self.psi_ext is None:
if self.phi_c is None:
self.psi_ext = np.ones(1)
else:
self.psi_ext = self.phi_c(x)
[docs] def _episode_end_update(self):
psi = np.concatenate((self.sum_grad_log, self.psi_ext))
self.sum_grad_log_list.append(psi)
[docs] def _init_update(self):
self.psi_ext = None
self.sum_grad_log = np.zeros(self.policy.weights_size)