DisCor: Corrective Feedback in Reinforcement Learning via Distribution Correction

TL;DR

DisCor introduces a distribution correction method for reinforcement learning that improves stability and performance by re-weighting training data, addressing issues caused by distribution mismatch and feedback loops.

Contribution

The paper proposes DisCor, a novel algorithm that approximates an optimal data distribution correction to enhance RL training stability and effectiveness.

Findings

DisCor significantly improves learning in noisy and sparse reward environments.

Theoretical analysis shows distribution correction reduces instability in Q-learning.

Empirical results demonstrate better convergence and performance across multiple tasks.

Abstract

Deep reinforcement learning can learn effective policies for a wide range of tasks, but is notoriously difficult to use due to instability and sensitivity to hyperparameters. The reasons for this remain unclear. When using standard supervised methods (e.g., for bandits), on-policy data collection provides "hard negatives" that correct the model in precisely those states and actions that the policy is likely to visit. We call this phenomenon "corrective feedback." We show that bootstrapping-based Q-learning algorithms do not necessarily benefit from this corrective feedback, and training on the experience collected by the algorithm is not sufficient to correct errors in the Q-function. In fact, Q-learning and related methods can exhibit pathological interactions between the distribution of experience collected by the agent and the policy induced by training on that experience, leading to potential instability, sub-optimal convergence, and poor results when learning from noisy, sparse or delayed rewards. We demonstrate the existence of this problem, both theoretically and empirically. We then show that a specific correction to the data distribution can mitigate this issue. Based on these observations, we propose a new algorithm, DisCor, which computes an approximation to this optimal distribution and uses it to re-weight the transitions used for training, resulting in substantial improvements in a range of challenging RL settings, such as multi-task learning and learning from noisy reward signals. Blog post presenting a summary of this work is available at: https://bair.berkeley.edu/blog/2020/03/16/discor/.