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This paper investigates off-policy evaluation in contextual bandits, aiming to quantify the performance of a target policy using data collected under a different and potentially unknown behavior policy. Recently, methods based on conformal…

Machine Learning · Statistics 2025-07-23 Yilong Wan , Yuqiang Li , Xianyi Wu

We use surrogate losses to obtain several new regret bounds and new algorithms for contextual bandit learning. Using the ramp loss, we derive new margin-based regret bounds in terms of standard sequential complexity measures of a benchmark…

Machine Learning · Computer Science 2018-11-06 Dylan J. Foster , Akshay Krishnamurthy

We consider a novel formulation of the multi-armed bandit model, which we call the contextual bandit with restricted context, where only a limited number of features can be accessed by the learner at every iteration. This novel formulation…

Artificial Intelligence · Computer Science 2017-06-09 Djallel Bouneffouf , Irina Rish , Guillermo A. Cecchi , Raphael Feraud

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 bandit learning in matching markets, where players and arms constitute the two market sides, and the players' utilities are linear in the arm contexts. In each round, new arms arrive with observable contexts. Then, the algorithm…

Machine Learning · Computer Science 2026-05-28 Shiyun Lin , Simon Mauras , Vianney Perchet , Nadav Merlis

In decision-making problems such as the multi-armed bandit, an agent learns sequentially by optimizing a certain feedback. While the mean reward criterion has been extensively studied, other measures that reflect an aversion to adverse…

Machine Learning · Statistics 2023-03-28 Patrick Saux , Odalric-Ambrym Maillard

Contextual bandit algorithms are ubiquitous tools for active sequential experimentation in healthcare and the tech industry. They involve online learning algorithms that adaptively learn policies over time to map observed contexts $X_t$ to…

Methodology · Statistics 2024-08-19 Ian Waudby-Smith , Lili Wu , Aaditya Ramdas , Nikos Karampatziakis , Paul Mineiro

This paper introduces a new principled approach for off-policy learning in contextual bandits. Unlike previous work, our approach does not derive learning principles from intractable or loose bounds. We analyse the problem through the…

Machine Learning · Statistics 2023-05-30 Otmane Sakhi , Pierre Alquier , Nicolas Chopin

Recent advances in learning techniques have garnered attention for their applicability to a diverse range of real-world sequential decision-making problems. Yet, many practical applications have critical constraints for operation in real…

Machine Learning · Computer Science 2024-05-06 Jose A. Ayala-Romero , Andres Garcia-Saavedra , Xavier Costa-Perez

A recurring theme in statistical learning, online learning, and beyond is that faster convergence rates are possible for problems with low noise, often quantified by the performance of the best hypothesis; such results are known as…

Machine Learning · Computer Science 2021-07-07 Dylan J. Foster , Akshay Krishnamurthy

To address the contextual bandit problem, we propose an online random forest algorithm. The analysis of the proposed algorithm is based on the sample complexity needed to find the optimal decision stump. Then, the decision stumps are…

Machine Learning · Computer Science 2016-09-16 Raphaël Féraud , Robin Allesiardo , Tanguy Urvoy , Fabrice Clérot

We consider the problem of contextual multi-armed bandits in the setting of hypothesis transfer learning. That is, we assume having access to a previously learned model on an unobserved set of contexts, and we leverage it in order to…

Machine Learning · Computer Science 2022-11-15 Steven Bilaj , Sofien Dhouib , Setareh Maghsudi

Contextual bandit with linear reward functions is among one of the most extensively studied models in bandit and online learning research. Recently, there has been increasing interest in designing \emph{locally private} linear contextual…

Machine Learning · Statistics 2024-04-16 Jiachun Li , David Simchi-Levi , Yining Wang

The contextual multi-armed bandit (MAB) problem is crucial in sequential decision-making. A line of research, known as online clustering of bandits, extends contextual MAB by grouping similar users into clusters, utilizing shared features…

Machine Learning · Computer Science 2025-01-03 Zhuohua Li , Maoli Liu , Xiangxiang Dai , John C. S. Lui

The contextual bandit has been identified as a powerful framework to formulate the recommendation process as a sequential decision-making process, where each item is regarded as an arm and the objective is to minimize the regret of $T$…

Machine Learning · Computer Science 2024-09-30 Yikun Ban , Yunzhe Qi , Tianxin Wei , Lihui Liu , Jingrui He

Intelligent agents equipped with causal knowledge can optimize their action spaces to avoid unnecessary exploration. The structural causal bandit framework provides a graphical characterization for identifying actions that are unable to…

Machine Learning · Computer Science 2025-11-25 Min Woo Park , Sanghack Lee

Many works have developed no-regret algorithms for contextual bandits with function approximation, where the mean reward function over context-action pairs belongs to a function class. Although there are many approaches to this problem, one…

Machine Learning · Computer Science 2025-03-18 Aldo Pacchiano

We study contextual bandit learning with an abstract policy class and continuous action space. We obtain two qualitatively different regret bounds: one competes with a smoothed version of the policy class under no continuity assumptions,…

Machine Learning · Statistics 2020-06-23 Akshay Krishnamurthy , John Langford , Aleksandrs Slivkins , Chicheng Zhang

Nonparametric contextual bandit is an important model of sequential decision making problems. Under $\alpha$-Tsybakov margin condition, existing research has established a regret bound of $\tilde{O}\left(T^{1-\frac{\alpha+1}{d+2}}\right)$…

Machine Learning · Computer Science 2025-05-09 Puning Zhao , Rongfei Fan , Shaowei Wang , Li Shen , Qixin Zhang , Zong Ke , Tianhang Zheng

We examine a multi-armed bandit problem with contextual information, where the objective is to ensure that each arm receives a minimum aggregated reward across contexts while simultaneously maximizing the total cumulative reward. This…

Machine Learning · Computer Science 2025-10-15 Ahmed Ben Yahmed , Hafedh El Ferchichi , Marc Abeille , Vianney Perchet