Thinking Fast and Slow with Deep Learning and Tree Search

TL;DR

This paper introduces Expert Iteration, a reinforcement learning method combining tree search and neural networks to improve decision-making in complex sequential tasks, outperforming existing algorithms and defeating top game players.

Contribution

The paper presents Expert Iteration, a novel algorithm that separates planning and generalisation, enhancing reinforcement learning performance in structured decision problems.

Findings

ExIt outperforms REINFORCE in Hex.

The trained agent defeats MoHex 1.0.

Tree search guided by neural networks improves planning.

Abstract

Sequential decision making problems, such as structured prediction, robotic control, and game playing, require a combination of planning policies and generalisation of those plans. In this paper, we present Expert Iteration (ExIt), a novel reinforcement learning algorithm which decomposes the problem into separate planning and generalisation tasks. Planning new policies is performed by tree search, while a deep neural network generalises those plans. Subsequently, tree search is improved by using the neural network policy to guide search, increasing the strength of new plans. In contrast, standard deep Reinforcement Learning algorithms rely on a neural network not only to generalise plans, but to discover them too. We show that ExIt outperforms REINFORCE for training a neural network to play the board game Hex, and our final tree search agent, trained tabula rasa, defeats MoHex 1.0, the most recent Olympiad Champion player to be publicly released.