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Poster
Breaking the Curse of Horizon: Infinite-Horizon Off-Policy Estimation
Qiang Liu · Lihong Li · Ziyang Tang · Denny Zhou

Wed Dec 05 02:00 PM -- 04:00 PM (PST) @ Room 517 AB #121
in Wed Poster Session B »

We consider the off-policy estimation problem of estimating the expected reward of a target policy using samples collected by a different behavior policy. Importance sampling (IS) has been a key technique to derive (nearly) unbiased estimators, but is known to suffer from an excessively high variance in long-horizon problems. In the extreme case of in infinite-horizon problems, the variance of an IS-based estimator may even be unbounded. In this paper, we propose a new off-policy estimation method that applies IS directly on the stationary state-visitation distributions to avoid the exploding variance issue faced by existing estimators.Our key contribution is a novel approach to estimating the density ratio of two stationary distributions, with trajectories sampled from only the behavior distribution. We develop a mini-max loss function for the estimation problem, and derive a closed-form solution for the case of RKHS. We support our method with both theoretical and empirical analyses.

Keywords: Density Estimation · Reinforcement Learning and Planning · Reinforcement Learning

Author Information

Qiang Liu (UT Austin)
Lihong Li (Google Brain)
Ziyang Tang (The University of Texas at Austin)
Denny Zhou (Google Brain)

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