Timezone: »

Near-Optimal Randomized Exploration for Tabular Markov Decision Processes
Zhihan Xiong · Ruoqi Shen · Qiwen Cui · Maryam Fazel · Simon Du

Tue Nov 29 09:30 AM -- 11:00 AM (PST) @ Hall J #317
We study algorithms using randomized value functions for exploration in reinforcement learning. This type of algorithms enjoys appealing empirical performance. We show that when we use 1) a single random seed in each episode, and 2) a Bernstein-type magnitude of noise, we obtain a worst-case $\widetilde{O}\left(H\sqrt{SAT}\right)$ regret bound for episodic time-inhomogeneous Markov Decision Process where $S$ is the size of state space, $A$ is the size of action space, $H$ is the planning horizon and $T$ is the number of interactions. This bound polynomially improves all existing bounds for algorithms based on randomized value functions, and for the first time, matches the $\Omega\left(H\sqrt{SAT}\right)$ lower bound up to logarithmic factors. Our result highlights that randomized exploration can be near-optimal, which was previously achieved only by optimistic algorithms. To achieve the desired result, we develop 1) a new clipping operation to ensure both the probability of being optimistic and the probability of being pessimistic are lower bounded by a constant, and 2) a new recursive formula for the absolute value of estimation errors to analyze the regret.

Author Information

Zhihan Xiong (University of Washington)
Ruoqi Shen (University of Washington)
Qiwen Cui (Department of Computer Science, University of Washington)
Maryam Fazel (University of Washington)
Simon Du (University of Washington)

More from the Same Authors