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This paper proposes a linear bandit algorithm that is adaptive to environments at two different levels of hierarchy. At the higher level, the proposed algorithm adapts to a variety of types of environments. More precisely, it achieves…

Machine Learning · Computer Science 2023-02-27 Shinji Ito , Kei Takemura

This paper studies batched bandit learning problems for nondegenerate functions. We introduce an algorithm that solves the batched bandit problem for nondegenerate functions near-optimally. More specifically, we introduce an algorithm,…

Machine Learning · Statistics 2025-04-09 Yu Liu , Yunlu Shu , Tianyu Wang

In this paper we consider the adversarial contextual bandit problem in metric spaces. The paper "Nearest neighbour with bandit feedback" tackled this problem but when there are many contexts near the decision boundary of the comparator…

Machine Learning · Computer Science 2023-12-18 Stephen Pasteris , Chris Hicks , Vasilios Mavroudis

We study the K-armed dueling bandit problem, a variation of the standard stochastic bandit problem where the feedback is limited to relative comparisons of a pair of arms. The hardness of recommending Copeland winners, the arms that beat…

Machine Learning · Statistics 2016-05-25 Junpei Komiyama , Junya Honda , Hiroshi Nakagawa

Linear bandits have a wide variety of applications including recommendation systems yet they make one strong assumption: the algorithms must know an upper bound $S$ on the norm of the unknown parameter $\theta^*$ that governs the reward…

Machine Learning · Statistics 2022-05-04 Spencer , Gales , Sunder Sethuraman , Kwang-Sung Jun

We study the stochastic multi-armed bandit problem when one knows the value $\mu^{(\star)}$ of an optimal arm, as a well as a positive lower bound on the smallest positive gap $\Delta$. We propose a new randomized policy that attains a…

Statistics Theory · Mathematics 2013-02-13 Sébastien Bubeck , Vianney Perchet , Philippe Rigollet

An adversarial bandit problem with memory constraints is studied where only the statistics of a subset of arms can be stored. A hierarchical learning policy that requires only a sublinear order of memory space in terms of the number of arms…

Machine Learning · Computer Science 2021-05-12 Xiao Xu , Qing Zhao

We consider a multi-armed bandit problem where payoffs are a linear function of an observed stochastic contextual variable. In the scenario where there exists a gap between optimal and suboptimal rewards, several algorithms have been…

Data Structures and Algorithms · Computer Science 2014-07-08 José Bento , Stratis Ioannidis , S. Muthukrishnan , Jinyun Yan

We derive improved regret bounds for the Tsallis-INF algorithm of Zimmert and Seldin (2021). We show that in adversarial regimes with a $(\Delta,C,T)$ self-bounding constraint the algorithm achieves $\mathcal{O}\left(\left(\sum_{i\neq i^*}…

Machine Learning · Computer Science 2021-09-14 Saeed Masoudian , Yevgeny Seldin

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 study the problem of adversarial combinatorial bandit with a switching cost $\lambda$ for a switch of each selected arm in each round, considering both the bandit feedback and semi-bandit feedback settings. In the oblivious adversarial…

Machine Learning · Statistics 2024-04-03 Yanyan Dong , Vincent Y. F. Tan

We consider minimisation of dynamic regret in non-stationary bandits with a slowly varying property. Namely, we assume that arms' rewards are stochastic and independent over time, but that the absolute difference between the expected…

Machine Learning · Computer Science 2021-10-26 Ramakrishnan Krishnamurthy , Aditya Gopalan

We study the adversarial multi-armed bandit problem where partial observations are available and where, in addition to the loss incurred for each action, a \emph{switching cost} is incurred for shifting to a new action. All previously known…

Machine Learning · Computer Science 2020-03-24 Raman Arora , Teodor V. Marinov , Mehryar Mohri

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

In this paper, we revisit the regret minimization problem in sparse stochastic contextual linear bandits, where feature vectors may be of large dimension $d$, but where the reward function depends on a few, say $s_0\ll d$, of these features…

Machine Learning · Statistics 2022-06-22 Kaito Ariu , Kenshi Abe , Alexandre Proutière

This paper investigates stochastic and adversarial combinatorial multi-armed bandit problems. In the stochastic setting under semi-bandit feedback, we derive a problem-specific regret lower bound, and discuss its scaling with the dimension…

Machine Learning · Computer Science 2015-11-09 Richard Combes , M. Sadegh Talebi , Alexandre Proutiere , Marc Lelarge

We consider the problem of learning in single-player and multiplayer multiarmed bandit models. Bandit problems are classes of online learning problems that capture exploration versus exploitation tradeoffs. In a multiarmed bandit model,…

Machine Learning · Statistics 2016-12-02 Naumaan Nayyar , Dileep Kalathil , Rahul Jain

In the classical multi-armed bandit problem, instance-dependent algorithms attain improved performance on "easy" problems with a gap between the best and second-best arm. Are similar guarantees possible for contextual bandits? While…

Machine Learning · Computer Science 2020-10-08 Dylan J. Foster , Alexander Rakhlin , David Simchi-Levi , Yunzong Xu

We give novel algorithms for multi-task and lifelong linear bandits with shared representation. Specifically, we consider the setting where we play $M$ linear bandits with dimension $d$, each for $T$ rounds, and these $M$ bandit tasks share…

Machine Learning · Computer Science 2022-03-30 Jiaqi Yang , Qi Lei , Jason D. Lee , Simon S. Du

We consider the problem of strongly-convex online optimization in presence of adversarial delays; in a T-iteration online game, the feedback of the player's query at time t is arbitrarily delayed by an adversary for d_t rounds and delivered…

Machine Learning · Computer Science 2019-09-12 Daniel Khashabi , Kent Quanrud , Amirhossein Taghvaei