Mastering Strategy Card Game (Legends of Code and Magic) via End-to-End Policy and Optimistic Smooth Fictitious Play

Deep Reinforcement Learning combined with Fictitious Play shows impressive results on many benchmark games, most of which are, however, single-stage. In contrast, real-world decision making problems may consist of multiple stages, where the observation spaces and the action spaces can be completely different across stages. We study a two-stage strategy card game Legends of Code and Magic and propose an end-to-end policy to address the difficulties that arise in multi-stage game. We also propose an optimistic smooth fictitious play algorithm to find the Nash Equilibrium for the two-player game. Our approach wins double championships of COG2022 competition. Extensive studies verify and show the advancement of our approach.

An Entropy Regularization Free Mechanism for Policy-based Reinforcement Learning

Policy-based reinforcement learning methods suffer from the policy collapse problem. We find valued-based reinforcement learning methods with {\epsilon}-greedy mechanism are capable of enjoying three characteristics, Closed-form Diversity, Objective-invariant Exploration and Adaptive Trade-off, which help value-based methods avoid the policy collapse problem. However, there does not exist a parallel mechanism for policy-based methods that achieves all three characteristics. In this paper, we propose an entropy regularization free mechanism that is designed for policy-based methods, which achieves Closed-form Diversity, Objective-invariant Exploration and Adaptive Trade-off. Our experiments show that our mechanism is super sample-efficient for policy-based methods and boosts a policy-based baseline to a new State-Of-The-Art on Arcade Learning Environment.

CASA: A Bridge Between Gradient of Policy Improvement and Policy Evaluation

This paper introduces a novel design of model-free reinforcement learning, CASA, Critic AS an Actor. CASA follows the actor-critic framework that estimates state-value, state-action-value and policy simultaneously. We prove that CASA integrates a consistent path for the policy evaluation and the policy improvement, which completely eliminates the gradient conflict between the policy improvement and the policy evaluation. The policy evaluation is equivalent to a compensational policy improvement, which alleviates the function approximation error, and is also equivalent to an entropy-regularized policy improvement, which prevents the policy from being trapped into a suboptimal solution. Building on this design, an expectation-correct Doubly Robust Trace is introduced to learn state-value and state-action-value, and the convergence is guaranteed. Our experiments show that the design achieves State-Of-The-Art on Arcade Learning Environment.