Offline Constrained Reinforcement Learning under Partial Data Coverage
Kihyuk Hong, Ambuj Tewari
TL;DR
The paper studies offline constrained reinforcement learning with partial data coverage and general function approximation, aiming to maximize a primary reward while meeting thresholds on auxiliary rewards using a fixed dataset. It introduces an LP-based, oracle-efficient primal-dual algorithm (PDORL) that leverages Lagrangian decomposition and a reparameterization trick to avoid policy extraction and knowledge of the data-generating distribution, under mild realizability assumptions. The authors show that saddle points of the restricted Lagrangian yield optimal policies and derive finite-sample guarantees with an $O(\epsilon^{-2})$ dependence, matching standard offline RL rates without requiring full data coverage. The framework naturally extends to constrained MDPs (CMDPs) with multiple rewards, Slater’s condition ensuring bounded duals, and corresponding near-feasibility and near-optimality guarantees, making the approach practical for safety-critical offline settings.
Abstract
We study offline constrained reinforcement learning (RL) with general function approximation. We aim to learn a policy from a pre-collected dataset that maximizes the expected discounted cumulative reward for a primary reward signal while ensuring that expected discounted returns for multiple auxiliary reward signals are above predefined thresholds. Existing algorithms either require fully exploratory data, are computationally inefficient, or depend on an additional auxiliary function classes to obtain an $ε$-optimal policy with sample complexity $O(ε^{-2})$. In this paper, we propose an oracle-efficient primal-dual algorithm based on a linear programming (LP) formulation, achieving $O(ε^{-2})$ sample complexity under partial data coverage. By introducing a realizability assumption, our approach ensures that all saddle points of the Lagrangian are optimal, removing the need for regularization that complicated prior analyses. Through Lagrangian decomposition, our method extracts policies without requiring knowledge of the data-generating distribution, enhancing practical applicability.
