Distributionally Robust Offline Reinforcement Learning with Linear Function Approximation

Among the reasons that hinder the application of reinforcement learning (RL) to real-world problems, two factors are critical: limited data and the mismatch of the testing environment compared to training one. In this paper, we attempt to address these issues simultaneously with the problem setup of distributionally robust offline RL. Particularly, we learn an RL agent with the historical data obtained from the source environment and optimize it to perform well in the perturbed one. Moreover, we consider the linear function approximation to apply the algorithm to large-scale problems. We prove our algorithm can achieve the suboptimality of $O(1/\sqrt{K})$ depending on the linear function dimension $d$, which seems to be the first result with sample complexity guarantee in this setting. Diverse experiments are conducted to demonstrate our theoretical findings, showing the superiority of our algorithm against the non-robust one.