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In this paper, we propose differentially private algorithms for the problem of stochastic linear bandits in the central, local and shuffled models. In the central model, we achieve almost the same regret as the optimal non-private…

Machine Learning · Computer Science 2022-07-08 Osama A. Hanna , Antonious M. Girgis , Christina Fragouli , Suhas Diggavi

This paper investigates the problem of best arm identification in $\textit{contaminated}$ stochastic multi-arm bandits. In this setting, the rewards obtained from any arm are replaced by samples from an adversarial model with probability…

Machine Learning · Computer Science 2021-11-16 Arpan Mukherjee , Ali Tajer , Pin-Yu Chen , Payel Das

The safe linear bandit problem (SLB) is an online approach to linear programming with unknown objective and unknown roundwise constraints, under stochastic bandit feedback of rewards and safety risks of actions. We study the tradeoffs…

Machine Learning · Computer Science 2024-07-02 Aditya Gangrade , Tianrui Chen , Venkatesh Saligrama

In a low-rank linear bandit problem, the reward of an action (represented by a matrix of size $d_1 \times d_2$) is the inner product between the action and an unknown low-rank matrix $\Theta^*$. We propose an algorithm based on a novel…

Machine Learning · Statistics 2020-10-20 Yangyi Lu , Amirhossein Meisami , Ambuj Tewari

We study finite-armed stochastic bandits where the rewards of each arm might be correlated to those of other arms. We introduce a novel phased algorithm that exploits the given structure to build confidence sets over the parameters of the…

Machine Learning · Computer Science 2020-05-26 Andrea Tirinzoni , Alessandro Lazaric , Marcello Restelli

We study best arm identification in a restless multi-armed bandit setting with finitely many arms. The discrete-time data generated by each arm forms a homogeneous Markov chain taking values in a common, finite state space. The state…

Machine Learning · Statistics 2024-06-25 P. N. Karthik , Vincent Y. F. Tan , Arpan Mukherjee , Ali Tajer

The improving multi-armed bandits problem is a formal model for allocating effort under uncertainty, motivated by scenarios such as investing research effort into new technologies, performing clinical trials, and hyperparameter selection…

Machine Learning · Computer Science 2026-05-22 Avrim Blum , Marten Garicano , Kavya Ravichandran , Dravyansh Sharma

We introduce vector optimization problems with stochastic bandit feedback, in which preferences among designs are encoded by a polyhedral ordering cone $C$. Our setup generalizes the best arm identification problem to vector-valued rewards…

Machine Learning · Computer Science 2023-03-09 Çağın Ararat , Cem Tekin

We consider the fixed-confidence best arm identification (FC-BAI) problem in the Bayesian setting. This problem aims to find the arm of the largest mean with a fixed confidence level when the bandit model has been sampled from the known…

Machine Learning · Statistics 2024-06-25 Kyoungseok Jang , Junpei Komiyama , Kazutoshi Yamazaki

We study linear contextual bandits in the misspecified setting, where the expected reward function can be approximated by a linear function class up to a bounded misspecification level $\zeta>0$. We propose an algorithm based on a novel…

Machine Learning · Computer Science 2023-03-17 Weitong Zhang , Jiafan He , Zhiyuan Fan , Quanquan Gu

We study bandit best-arm identification with arbitrary and potentially adversarial rewards. A simple random uniform learner obtains the optimal rate of error in the adversarial scenario. However, this type of strategy is suboptimal when the…

Machine Learning · Statistics 2026-04-17 Yasin Abbasi-Yadkori , Peter L. Bartlett , Victor Gabillon , Alan Malek , Michal Valko

We propose a novel linear bandit algorithm called LinMED (Linear Minimum Empirical Divergence), which is a linear extension of the MED algorithm that was originally designed for multi-armed bandits. LinMED is a randomized algorithm that…

Machine Learning · Statistics 2025-03-12 Kapilan Balagopalan , Kwang-Sung Jun

In this paper we consider the problem of best-arm identification in multi-armed bandits in the fixed confidence setting, where the goal is to identify, with probability $1-\delta$ for some $\delta>0$, the arm with the highest mean reward in…

Machine Learning · Statistics 2021-09-13 Samarth Gupta , Gauri Joshi , Osman Yağan

We focus on the problem of best-arm identification in a stochastic multi-arm bandit with temporally decreasing variances for the arms' rewards. We model arm rewards as Gaussian random variables with fixed means and variances that decrease…

Machine Learning · Computer Science 2025-02-12 Tamojeet Roychowdhury , Kota Srinivas Reddy , Krishna P Jagannathan , Sharayu Moharir

Recently, high dimensional vector auto-regressive models (VAR), have attracted a lot of interest, due to novel applications in the health, engineering and social sciences. The presence of temporal dependence poses additional challenges to…

Statistics Theory · Mathematics 2022-09-20 Sagnik Halder , George Michailidis

We study the combinatorial pure exploration problem Best-Set in stochastic multi-armed bandits. In a Best-Set instance, we are given $n$ arms with unknown reward distributions, as well as a family $\mathcal{F}$ of feasible subsets over the…

Machine Learning · Computer Science 2017-06-06 Lijie Chen , Anupam Gupta , Jian Li , Mingda Qiao , Ruosong Wang

We consider a stochastic continuum armed bandit problem where the arms are indexed by the $\ell_2$ ball $B_{d}(1+\nu)$ of radius $1+\nu$ in $\mathbb{R}^d$. The reward functions $r :B_{d}(1+\nu) \rightarrow \mathbb{R}$ are considered to…

Machine Learning · Statistics 2017-05-31 Hemant Tyagi , Sebastian Stich , Bernd Gärtner

We study the problem of identifying the best arm in a stochastic multi-armed bandit game. Given a set of $n$ arms indexed from $1$ to $n$, each arm $i$ is associated with an unknown reward distribution supported on $[0,1]$ with mean…

Machine Learning · Computer Science 2023-05-30 Pinyan Lu , Chao Tao , Xiaojin Zhang

Recently multi-armed bandit problem arises in many real-life scenarios where arms must be sampled in batches, due to limited time the agent can wait for the feedback. Such applications include biological experimentation and online…

Machine Learning · Statistics 2023-12-22 Shengyu Cao , Simai He , Ruoqing Jiang , Jin Xu , Hongsong Yuan

In this paper, we study the problem of stochastic linear bandits with finite action sets. Most of existing work assume the payoffs are bounded or sub-Gaussian, which may be violated in some scenarios such as financial markets. To settle…

Machine Learning · Computer Science 2020-04-29 Bo Xue , Guanghui Wang , Yimu Wang , Lijun Zhang