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We consider the adversarial linear contextual bandit setting, which allows for the loss functions associated with each of $K$ arms to change over time without restriction. Assuming the $d$-dimensional contexts are drawn from a fixed known…

Machine Learning · Computer Science 2023-05-25 Julia Olkhovskaya , Jack Mayo , Tim van Erven , Gergely Neu , Chen-Yu Wei

We study high-dimensional multi-armed contextual bandits with batched feedback where the $T$ steps of online interactions are divided into $L$ batches. In specific, each batch collects data according to a policy that depends on previous…

Machine Learning · Statistics 2023-11-27 Jianqing Fan , Zhaoran Wang , Zhuoran Yang , Chenlu Ye

We propose the first contextual bandit algorithm that is parameter-free, efficient, and optimal in terms of dynamic regret. Specifically, our algorithm achieves dynamic regret $\mathcal{O}(\min\{\sqrt{ST},…

Machine Learning · Computer Science 2019-06-19 Yifang Chen , Chung-Wei Lee , Haipeng Luo , Chen-Yu Wei

In this paper, we investigate the existence of online learning algorithms with bandit feedback that simultaneously guarantee $O(1)$ regret compared to a given comparator strategy, and $\tilde{O}(\sqrt{T})$ regret compared to any fixed…

Machine Learning · Computer Science 2025-06-05 Adrian Müller , Jon Schneider , Stratis Skoulakis , Luca Viano , Volkan Cevher

We study stochastic linear optimization problem with bandit feedback. The set of arms take values in an $N$-dimensional space and belong to a bounded polyhedron described by finitely many linear inequalities. We provide a lower bound for…

Machine Learning · Computer Science 2015-09-29 Manjesh K. Hanawal , Amir Leshem , Venkatesh Saligrama

We study stochastic linear bandits where, in each round, the learner receives a set of actions (i.e., feature vectors), from which it chooses an element and obtains a stochastic reward. The expected reward is a fixed but unknown linear…

Machine Learning · Computer Science 2024-06-04 Tianyuan Jin , Kyoungseok Jang , Nicolò Cesa-Bianchi

We give a randomized online algorithm that guarantees near-optimal $\widetilde O(\sqrt T)$ expected swap regret against any sequence of $T$ adaptively chosen Lipschitz convex losses on the unit interval. This improves the previous best…

Machine Learning · Computer Science 2026-02-10 Lunjia Hu , Jon Schneider , Yifan Wu

Cascading bandits is a natural and popular model that frames the task of learning to rank from Bernoulli click feedback in a bandit setting. For the case of unstructured rewards, we prove matching upper and lower bounds for the…

Machine Learning · Computer Science 2022-10-11 Daniel Vial , Sujay Sanghavi , Sanjay Shakkottai , R. Srikant

We study the stochastic linear bandit problem with multiple arms over $T$ rounds, where the covariate dimension $d$ may exceed $T$, but each arm-specific parameter vector is $s$-sparse. We begin by analyzing the sequential estimation…

Statistics Theory · Mathematics 2025-05-26 Jingyu Liu , Yanglei Song

Contextual bandits are widely used in Internet services from news recommendation to advertising, and to Web search. Generalized linear models (logistical regression in particular) have demonstrated stronger performance than linear models in…

Machine Learning · Computer Science 2017-06-20 Lihong Li , Yu Lu , Dengyong Zhou

Unlike classical control theory, such as Linear Quadratic Control (LQC), real-world control problems are highly complex. These problems often involve adversarial perturbations, bandit feedback models, and non-quadratic, adversarially chosen…

Machine Learning · Computer Science 2024-10-03 Y. Jennifer Sun , Zhou Lu

We study small-loss bounds for adversarial multi-armed bandits with graph feedback, that is, adaptive regret bounds that depend on the loss of the best arm or related quantities, instead of the total number of rounds. We derive the first…

Machine Learning · Computer Science 2020-06-24 Chung-Wei Lee , Haipeng Luo , Mengxiao Zhang

We investigate the high-dimensional sparse linear bandits problem in a data-poor regime where the time horizon is much smaller than the ambient dimension and number of arms. We study the setting under the additional blocking constraint…

Machine Learning · Computer Science 2025-05-30 Adit Jain , Soumyabrata Pal , Sunav Choudhary , Ramasuri Narayanam , Harshita Chopra , Vikram Krishnamurthy

In this paper, we consider the problem of sequentially optimizing a black-box function $f$ based on noisy samples and bandit feedback. We assume that $f$ is smooth in the sense of having a bounded norm in some reproducing kernel Hilbert…

Machine Learning · Statistics 2018-06-01 Jonathan Scarlett , Ilijia Bogunovic , Volkan Cevher

We investigate the sparse linear contextual bandit problem where the parameter $\theta$ is sparse. To relieve the sampling inefficiency, we utilize the "perturbed adversary" where the context is generated adversarilly but with small random…

Machine Learning · Computer Science 2020-07-20 Zhiyuan Liu , Huazheng Wang , Bo Waggoner , Youjian , Liu , Lijun Chen

We consider a linear stochastic bandit problem involving $M$ agents that can collaborate via a central server to minimize regret. A fraction $\alpha$ of these agents are adversarial and can act arbitrarily, leading to the following tension:…

Machine Learning · Computer Science 2022-06-08 Aritra Mitra , Arman Adibi , George J. Pappas , Hamed Hassani

Risk-sensitive linear quadratic regulator is one of the most fundamental problems in risk-sensitive optimal control. In this paper, we study online adaptive control of risk-sensitive linear quadratic regulator in the finite horizon episodic…

Machine Learning · Computer Science 2025-02-14 Wenhao Xu , Xuefeng Gao , Xuedong He

We consider the problem of combining and learning over a set of adversarial bandit algorithms with the goal of adaptively tracking the best one on the fly. The CORRAL algorithm of Agarwal et al. (2017) and its variants (Foster et al.,…

Machine Learning · Computer Science 2022-02-15 Haipeng Luo , Mengxiao Zhang , Peng Zhao , Zhi-Hua Zhou

We consider a stochastic sparse linear bandit problem where only a sparse subset of context features affects the expected reward function, i.e., the unknown reward parameter has a sparse structure. In the existing Lasso bandit literature,…

Machine Learning · Statistics 2025-03-04 Harin Lee , Taehyun Hwang , Min-hwan Oh

We study the constrained variant of the \emph{multi-armed bandit} (MAB) problem, in which the learner aims not only at minimizing the total loss incurred during the learning dynamic, but also at controlling the violation of multiple…

Machine Learning · Computer Science 2026-02-17 Francesco Emanuele Stradi , Kalana Kalupahana , Matteo Castiglioni , Alberto Marchesi , Nicola Gatti