Safe Policy Learning from Observations
Authors: Elad Sarafian, Aviv Tamar, Sarit Kraus
Keywords: learning from observations, safe reinforcement learning, deep reinforcement learning
TL;DR: An algorithm for learning to improve upon the behavior demonstrated by multiple unknown policies, by combining imitation learning and a novel safe policy improvement step that is resilient to value estimation errors.
Abstract: In this paper, we consider the problem of learning a policy by observing numerous non-expert agents. Our goal is to extract a policy that, with high-confidence, acts better than the agents' average performance. Such a setting is important for real-world problems where expert data is scarce but non-expert data can easily be obtained, e.g. by crowdsourcing. Our approach is to pose this problem as safe policy improvement in reinforcement learning. First, we evaluate an average behavior policy and approximate its value function. Then, we develop a stochastic policy improvement algorithm that safely improves the average behavior. The primary advantages of our approach, termed Rerouted Behavior Improvement (RBI), over other safe learning methods are its stability in the presence of value estimation errors and the elimination of a policy search process.  We demonstrate these advantages in the Taxi grid-world domain and in four games from the Atari learning environment.