Reviews: Maximum Entropy Monte-Carlo Planning

This paper proposes a new MCTS algorithm, Maximum Entropy for Tree Search (MENTS), which combines the maximum entropy policy optimization framework with MCTS for more efficient online planning in sequential decision problems. The main idea is to replace the Monte Carlo value estimate with the softmax value estimate as in the maximum entropy policy optimization framework, such that the state value can be estimated and back-propagated more efficiently in the search tree. Another main novelty is that it proposes an optimal algorithm, Empirical Exponential Weight (E2W), to be the tree policy to do more exploration. It shows that MENTS can achieve an exponential convergence rate towards finding the optimal action at the root of the tree, which is much faster than the polynomial convergence rate of the UCT method. The experimental results also demonstrate that MENTS performs significantly better than UCT in terms of sample efficiency, in both synthetic problems and Atari games.