Modular Multitask Reinforcement Learning with Policy Sketches

TL;DR

This paper introduces a modular multitask reinforcement learning framework guided by high-level policy sketches, enabling efficient learning of shared subpolicies and rapid adaptation to new tasks with interpretable primitives.

Contribution

It proposes a novel approach that uses policy sketches to guide multitask RL, learning shared subpolicies without detailed guidance, and demonstrates improved performance and interpretability.

Findings

Outperforms existing methods on discrete and continuous control tasks.

Learns a library of interpretable primitive behaviors.

Enables rapid adaptation to new tasks through recombination.

Abstract

We describe a framework for multitask deep reinforcement learning guided by policy sketches. Sketches annotate tasks with sequences of named subtasks, providing information about high-level structural relationships among tasks but not how to implement them---specifically not providing the detailed guidance used by much previous work on learning policy abstractions for RL (e.g. intermediate rewards, subtask completion signals, or intrinsic motivations). To learn from sketches, we present a model that associates every subtask with a modular subpolicy, and jointly maximizes reward over full task-specific policies by tying parameters across shared subpolicies. Optimization is accomplished via a decoupled actor--critic training objective that facilitates learning common behaviors from multiple dissimilar reward functions. We evaluate the effectiveness of our approach in three environments featuring both discrete and continuous control, and with sparse rewards that can be obtained only after completing a number of high-level subgoals. Experiments show that using our approach to learn policies guided by sketches gives better performance than existing techniques for learning task-specific or shared policies, while naturally inducing a library of interpretable primitive behaviors that can be recombined to rapidly adapt to new tasks.