PROJECTED STATE-ACTION BALANCING WEIGHTS FOR OFFLINE REINFORCEMENT LEARNING

• 成果类型: Article
• 署名作者: Wang, Jiayi; Qi, Zhengling; Wong, Raymond K. W.
• 署名单位: University of Texas System; University of Texas Dallas; George Washington University; Texas A&M University System; Texas A&M University College Station
• 刊物名称: ANNALS OF STATISTICS
• ISSN/ISSBN: 0090-5364
• DOI: 10.1214/23-AOS2302
• 发表日期: 2023
• 页码: 1639-1665
• 关键词: dynamic treatment regimes; rates; CONVERGENCE; inference

摘要

Off-policy evaluation is considered a fundamental and challenging problem in reinforcement learning (RL). This paper focuses on value estimation of a target policy based on pre-collected data generated from a possibly different policy, under the framework of infinite-horizon Markov decision processes. Motivated by the recently developed marginal importance sampling method in RL and the covariate balancing idea in causal inference, we propose a novel estimator with approximately projected state-action balancing weights for the policy value estimation. We obtain the convergence rate of these weights, and show that the proposed value estimator is asymptotically normal under technical conditions. In terms of asymptotics, our results scale with both the number of trajectories and the number of decision points at each trajectory. As such, consistency can still be achieved with a limited number of subjects when the number of decision points diverges. In addition, we develop a necessary and sufficient condition for establishing the well-posedness of the operator that relates to the nonparametric Q-function estimation in the off-policy setting, which characterizes the difficulty of Q-function estimation and may be of independent interest. Numerical experiments demonstrate the promising performance of our proposed estimator.