Policy Information Capacity: Information-Theoretic Measure for Task Complexity in Deep Reinforcement Learning

Abstract

Progress in deep reinforcement learning (RL) research is largely enabled by benchmark task environments. However, analyzing the nature of those environments is often overlooked. In particular, we still do not have agreeable ways to measure the difficulty or solvability of a task, given that each has fundamentally different actions, observations, dynamics, rewards, and can be tackled with diverse RL algorithms. In this work, we propose policy information capacity (PIC) – the mutual information between policy parameters and episodic return – and policy-optimal information capacity (POIC) – between policy parameters and episodic optimality – as two environment-agnostic, algorithm-agnostic quantitative metrics for task difficulty. Evaluating our metrics across toy environments as well as continuous control benchmark tasks from OpenAI Gym and DeepMind Control Suite, we empirically demonstrate that these information-theoretic metrics have higher correlations with normalized task solvability scores than a variety of alternatives. Lastly, we show that these metrics can also be used for fast and compute-efficient optimizations of key design parameters such as reward shaping, policy architectures, and MDP properties for better solvability by RL algorithms without ever running full RL experiments.

Hiroki Furuta

Ph.D. student

Tatsuya Matsushima

Project Researcher

My research interests include robot learning, robot system, and XR.

Yutaka Matsuo

Professor

Shixiang Shane Gu

Visiting Associate Professor

Shixiang Shane Gu is a Senior Research Scientist at Google Brain, and a Visiting Associate Professor at the University of Tokyo, with research interests around (1) algorithmic problems in deep learning, reinforcement learning, robotics, and probabilistic machine learning, and (2) mastering a universal physics prior for continuous control. website