arXiv Machine Learning By Kushagra Chandak, Volodymyr Tkachuk, Xiaoqi Tan, Csaba Szepesv\'ari

Gaussian-Width Bounds for Offline-to-Online Linear Bandits

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The paper investigates how offline data can improve online learning in stochastic linear bandits, focusing on the case where only a subset of feature directions is poorly covered. It shows that previous regret bounds of ≥O(√{dkT}) stem from loose reward prediction error control and derives tighter bounds using concentration of Lipschitz functions of Gaussian vectors. The authors propose a phased elimination algorithm achieving regret ≥O(k√T) and establish matching lower bounds for both partial and uniform coverage, while also addressing pure exploration with offline data and providing matching bounds for simple regret.

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arXiv Machine Learning
Jul 7

Dynamic Regret for Non-Stationary Linear Bandits via Misspecification Reductions

arXiv:2607. 02891v1 Announce Type: new Abstract: Many online decision-making problems involve both round-specific feasible actions and drifting reward models: eligible ad impressions, feasible prices, and available treatments can change over time, while user preferences, demand curves, and patient responses may evolve.

By Zihao Hu, Yuan Yao, Jiheng Zhang, Zhengyuan Zhou