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We develop a general theory to optimize the frequentist regret for sequential learning problems, where efficient bandit and reinforcement learning algorithms can be derived from unified Bayesian principles. We propose a novel optimization…

Machine Learning · Computer Science 2024-02-12 Yunbei Xu , Assaf Zeevi

Contextual bandit algorithms are essential for solving real-world decision making problems. In practice, collecting a contextual bandit's feedback from different domains may involve different costs. For example, measuring drug reaction from…

Machine Learning · Computer Science 2025-04-08 Ziyan Wang , Xiaoming Huo , Hao Wang

Combinatorial multi-armed bandits provide a fundamental online decision-making environment where a decision-maker interacts with an environment across $T$ time steps, each time selecting an action and learning the cost of that action. The…

Machine Learning · Computer Science 2026-04-13 Gerdus Benadè , Rathish Das , Thomas Lavastida

We study budget-constrained contextual bandits with adversarial contexts, where each action yields a random reward and incurs a random cost. We adopt the standard realizability assumption: conditioned on the observed context, rewards and…

Machine Learning · Computer Science 2026-05-08 Dhruv Sarkar , Abhishek Sinha

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 propose online algorithms for sequential learning in the contextual multi-armed bandit setting. Our approach is to partition the context space and then optimally combine all of the possible mappings between the partition regions and the…

Machine Learning · Computer Science 2017-12-11 Mohammadreza Mohaghegh Neyshabouri , Kaan Gokcesu , Huseyin Ozkan , Suleyman S. Kozat

While contextual bandit has a mature theory, effectively leveraging different feedback patterns to enhance the pace of learning remains unclear. Bandits with feedback graphs, which interpolates between the full information and bandit…

Machine Learning · Computer Science 2023-10-30 Mengxiao Zhang , Yuheng Zhang , Olga Vrousgou , Haipeng Luo , Paul Mineiro

We study a generalization of the problem of online learning in adversarial linear contextual bandits by incorporating loss functions that belong to a reproducing kernel Hilbert space, which allows for a more flexible modeling of complex…

Machine Learning · Statistics 2023-10-04 Gergely Neu , Julia Olkhovskaya , Sattar Vakili

This paper studies semiparametric contextual bandits, a generalization of the linear stochastic bandit problem where the reward for an action is modeled as a linear function of known action features confounded by an non-linear…

Machine Learning · Statistics 2018-07-17 Akshay Krishnamurthy , Zhiwei Steven Wu , Vasilis Syrgkanis

We study the problem of $K$-armed dueling bandit for both stochastic and adversarial environments, where the goal of the learner is to aggregate information through relative preferences of pair of decisions points queried in an online…

Machine Learning · Computer Science 2022-02-15 Aadirupa Saha , Pierre Gaillard

We study a novel variant of the multi-armed bandit problem, where at each time step, the player observes an independently sampled context that determines the arms' mean rewards. However, playing an arm blocks it (across all contexts) for a…

Machine Learning · Computer Science 2020-06-18 Soumya Basu , Orestis Papadigenopoulos , Constantine Caramanis , Sanjay Shakkottai

A standard assumption in contextual multi-arm bandit is that the true context is perfectly known before arm selection. Nonetheless, in many practical applications (e.g., cloud resource management), prior to arm selection, the context…

Machine Learning · Computer Science 2021-04-06 Jianyi Yang , Shaolei Ren

We give an oracle-based algorithm for the adversarial contextual bandit problem, where either contexts are drawn i.i.d. or the sequence of contexts is known a priori, but where the losses are picked adversarially. Our algorithm is…

Machine Learning · Computer Science 2016-06-02 Vasilis Syrgkanis , Haipeng Luo , Akshay Krishnamurthy , Robert E. Schapire

We present regret minimization algorithms for the contextual multi-armed bandit (CMAB) problem over $K$ actions in the presence of delayed feedback, a scenario where loss observations arrive with delays chosen by an adversary. As a…

Machine Learning · Computer Science 2025-10-13 Orin Levy , Liad Erez , Alon Cohen , Yishay Mansour

We propose a linear contextual bandit algorithm with $O(\sqrt{dT\log T})$ regret bound, where $d$ is the dimension of contexts and $T$ isthe time horizon. Our proposed algorithm is equipped with a novel estimator in which exploration is…

Machine Learning · Statistics 2023-03-30 Wonyoung Kim , Myunghee Cho Paik , Min-hwan Oh

We study the linear contextual bandit problem in the presence of adversarial corruption, where the reward at each round is corrupted by an adversary, and the corruption level (i.e., the sum of corruption magnitudes over the horizon) is…

Machine Learning · Computer Science 2022-07-12 Jiafan He , Dongruo Zhou , Tong Zhang , Quanquan Gu

This paper addresses the poor finite-horizon performance of existing online \emph{restless bandit} (RB) algorithms, which stems from the prohibitive sample complexity of learning a full \emph{Markov decision process} (MDP) for each agent.…

Machine Learning · Computer Science 2026-04-07 Jiamin Xu , Ivan Nazarov , Aditya Rastogi , África Periáñez , Kyra Gan

We study the problem of representation learning in stochastic contextual linear bandits. While the primary concern in this domain is usually to find realizable representations (i.e., those that allow predicting the reward function at any…

Machine Learning · Computer Science 2022-10-25 Andrea Tirinzoni , Matteo Papini , Ahmed Touati , Alessandro Lazaric , Matteo Pirotta

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

Standard approaches to decision-making under uncertainty focus on sequential exploration of the space of decisions. However, \textit{simultaneously} proposing a batch of decisions, which leverages available resources for parallel…

Machine Learning · Statistics 2023-02-07 Jeffrey Chan , Aldo Pacchiano , Nilesh Tripuraneni , Yun S. Song , Peter Bartlett , Michael I. Jordan