Abstract

Recent theoretical work studies sample-efficient reinforcement learning (RL) extensively in two settings: learning interactively in the environment (online RL), or learning from an offline dataset (offline RL). However, existing algorithms and theories for learning near-optimal policies in these two settings are rather different and disconnected. Towards bridging this gap, this paper initiates the theoretical study of policy finetuning, that is, online RL where the learner has additional access to a "reference policy" \(\mu\) close to the optimal policy \(\pi_\star\) in a certain sense. We consider the policy finetuning problem in episodic Markov Decision Processes (MDPs) with \(S\) states, \(A\) actions, and horizon length \(H\). We first design a sharp offline reduction algorithm -- which simply executes \(\mu\) and runs offline policy optimization on the collected dataset -- that finds an \(\epsilon\) near-optimal policy within \(\widetilde\{O\}(H^3SC^\star/\epsilon^2)\) episodes, w

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Tags

  • Offline RL
  • Policy Gradient

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