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We consider a novel variant of the contextual bandit problem (i.e., the multi-armed bandit with side-information, or context, available to a decision-maker) where the reward associated with each context-based decision may not always be…

Machine Learning · Computer Science 2020-07-21 Djallel Bouneffouf , Sohini Upadhyay , Yasaman Khazaeni

Contextual bandit algorithms are sensitive to the estimation method of the outcome model as well as the exploration method used, particularly in the presence of rich heterogeneity or complex outcome models, which can lead to difficult…

Machine Learning · Statistics 2018-12-18 Maria Dimakopoulou , Zhengyuan Zhou , Susan Athey , Guido Imbens

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

Contextual bandits are canonical models for sequential decision-making under uncertainty in environments with time-varying components. In this setting, the expected reward of each bandit arm consists of the inner product of an unknown…

Machine Learning · Statistics 2022-05-27 Hongju Park , Mohamad Kazem Shirani Faradonbeh

Contextual bandit algorithms are essential for solving many real-world interactive machine learning problems. Despite multiple recent successes on statistically and computationally efficient methods, the practical behavior of these…

Machine Learning · Statistics 2021-06-08 Alberto Bietti , Alekh Agarwal , John Langford

We consider the contextual combinatorial bandit setting where in each round, the learning agent, e.g., a recommender system, selects a subset of "arms," e.g., products, and observes rewards for both the individual base arms, which are a…

Machine Learning · Computer Science 2025-04-22 Baran Atalar , Carlee Joe-Wong

In this paper, we investigate the impact of context diversity on stochastic linear contextual bandits. As opposed to the previous view that contexts lead to more difficult bandit learning, we show that when the contexts are sufficiently…

Machine Learning · Computer Science 2020-03-06 Weiqiang Wu , Jing Yang , Cong Shen

Recommender systems relying on contextual multi-armed bandits continuously improve relevant item recommendations by taking into account the contextual information. The objective of bandit algorithms is to learn the best arm (e.g., best item…

Machine Learning · Computer Science 2025-12-10 Ahmed Sayeed Faruk , Elena Zheleva

The Rising Multi-Armed Bandit (RMAB) framework models environments where expected rewards of arms increase with plays, which models practical scenarios where performance of each option improves with the repeated usage, such as in robotics…

Machine Learning · Computer Science 2026-02-16 Seockbean Song , Chenyu Gan , Youngsik Yoon , Siwei Wang , Wei Chen , Jungseul Ok

We consider a stochastic multi-armed bandit setting and study the problem of constrained regret minimization over a given time horizon. Each arm is associated with an unknown, possibly multi-dimensional distribution, and the merit of an arm…

Machine Learning · Computer Science 2023-01-05 Anmol Kagrecha , Jayakrishnan Nair , Krishna Jagannathan

Classic contextual bandit algorithms for linear models, such as LinUCB, assume that the reward distribution for an arm is modeled by a stationary linear regression. When the linear regression model is non-stationary over time, the regret of…

Machine Learning · Statistics 2020-02-14 Qin Ding , Cho-Jui Hsieh , James Sharpnack

Contextual bandit learning is a reinforcement learning problem where the learner repeatedly receives a set of features (context), takes an action and receives a reward based on the action and context. We consider this problem under a…

Machine Learning · Computer Science 2012-03-05 Alekh Agarwal , Miroslav Dudík , Satyen Kale , John Langford , Robert E. Schapire

Contextual multi-armed bandit (MAB) algorithms have been shown promising for maximizing cumulative rewards in sequential decision tasks such as news article recommendation systems, web page ad placement algorithms, and mobile health.…

Machine Learning · Statistics 2019-02-01 Gi-Soo Kim , Myunghee Cho Paik

We consider the stochastic contextual bandit problem with additional regularization. The motivation comes from problems where the policy of the agent must be close to some baseline policy which is known to perform well on the task. To…

Machine Learning · Statistics 2019-06-06 Xavier Fontaine , Quentin Berthet , Vianney Perchet

Standard contextual bandit problem assumes that all the relevant contexts are observed before the algorithm chooses an arm. This modeling paradigm, while useful, often falls short when dealing with problems in which valuable additional…

Machine Learning · Computer Science 2023-09-26 Chaoqi Wang , Ziyu Ye , Zhe Feng , Ashwinkumar Badanidiyuru , Haifeng Xu

Contextual dueling bandit is used to model the bandit problems, where a learner's goal is to find the best arm for a given context using observed noisy human preference feedback over the selected arms for the past contexts. However,…

Machine Learning · Computer Science 2025-04-17 Arun Verma , Zhongxiang Dai , Xiaoqiang Lin , Patrick Jaillet , Bryan Kian Hsiang Low

In many real-world applications, multiple agents seek to learn how to perform highly related yet slightly different tasks in an online bandit learning protocol. We formulate this problem as the $\epsilon$-multi-player multi-armed bandit…

Machine Learning · Computer Science 2021-07-21 Zhi Wang , Chicheng Zhang , Manish Kumar Singh , Laurel D. Riek , Kamalika Chaudhuri

Contextual multi-armed bandit has shown to be an effective tool in recommender systems. In this paper, we study a novel problem of multi-facet bandits involving a group of bandits, each characterizing the users' needs from one unique…

Machine Learning · Computer Science 2021-07-02 Yikun Ban , Jingrui He , Curtiss B. Cook

Contextual Multi-Armed Bandits is a well-known and accepted online optimization algorithm, that is used in many Web experiences to tailor content or presentation to users' traffic. Much has been published on theoretical guarantees (e.g.…

Information Retrieval · Computer Science 2019-07-12 David Abensur , Ivan Balashov , Shaked Bar , Ronny Lempel , Nurit Moscovici , Ilan Orlov , Danny Rosenstein , Ido Tamir

Contextual bandits are widely-used in the study of learning-based control policies for finite action spaces. While the problem is well-studied for bandits with perfectly observed context vectors, little is known about the case of…

Machine Learning · Statistics 2022-02-03 Hongju Park , Mohamad Kazem Shirani Faradonbeh