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We consider the problem where M agents collaboratively interact with an instance of a stochastic K-armed contextual bandit, where K>>M. The goal of the agents is to simultaneously minimize the cumulative regret over all the agents over a…

Machine Learning · Computer Science 2022-11-16 Jiabin Lin , Shana Moothedath

We present conservative distributed multi-task learning in stochastic linear contextual bandits with heterogeneous agents. This extends conservative linear bandits to a distributed setting where M agents tackle different but related tasks…

Machine Learning · Computer Science 2025-04-29 Jiabin Lin , Shana Moothedath

Learning in multi-player games can model a large variety of practical scenarios, where each player seeks to optimize its own local objective function, which at the same time relies on the actions taken by others. Motivated by the frequent…

Optimization and Control · Mathematics 2023-09-08 Yuanhanqing Huang , Jianghai Hu

We provide the first oracle efficient sublinear regret algorithms for adversarial versions of the contextual bandit problem. In this problem, the learner repeatedly makes an action on the basis of a context and receives reward for the…

Machine Learning · Computer Science 2016-02-09 Vasilis Syrgkanis , Akshay Krishnamurthy , Robert E. Schapire

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 · Computer Science 2018-12-18 Maria Dimakopoulou , Zhengyuan Zhou , Susan Athey , Guido Imbens

Model selection in contextual bandits is an important complementary problem to regret minimization with respect to a fixed model class. We consider the simplest non-trivial instance of model-selection: distinguishing a simple multi-armed…

Machine Learning · Computer Science 2022-07-01 Vidya Muthukumar , Akshay Krishnamurthy

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

We study lifelong learning in linear bandits, where a learner interacts with a sequence of linear bandit tasks whose parameters lie in an $m$-dimensional subspace of $\mathbb{R}^d$, thereby sharing a low-rank representation. Current…

Machine Learning · Computer Science 2025-01-24 Thang Duong , Zhi Wang , Chicheng Zhang

We consider a linear stochastic bandit problem involving $M$ agents that can collaborate via a central server to minimize regret. A fraction $\alpha$ of these agents are adversarial and can act arbitrarily, leading to the following tension:…

Machine Learning · Computer Science 2022-06-08 Aritra Mitra , Arman Adibi , George J. Pappas , Hamed Hassani

We consider a sequential assortment selection problem where the user choice is given by a multinomial logit (MNL) choice model whose parameters are unknown. In each period, the learning agent observes a $d$-dimensional contextual…

Machine Learning · Statistics 2021-03-26 Min-hwan Oh , Garud Iyengar

We consider an online decision making setting known as contextual bandit problem, and propose an approach for improving contextual bandit performance by using an adaptive feature extraction (representation learning) based on online…

Artificial Intelligence · Computer Science 2020-09-15 Baihan Lin , Djallel Bouneffouf , Guillermo Cecchi , Irina Rish

We consider the kernelized contextual bandit problem with a large feature space. This problem involves $K$ arms, and the goal of the forecaster is to maximize the cumulative rewards through learning the relationship between the contexts and…

Machine Learning · Statistics 2025-05-21 Shogo Iwazaki , Junpei Komiyama , Masaaki Imaizumi

A key goal in stochastic contextual linear bandits is to efficiently learn a near-optimal policy. Prior algorithms for this problem learn a policy by strategically sampling actions but naively (passively) sampling contexts from the…

Machine Learning · Computer Science 2026-05-26 Emma Brunskill , Ishani Karmarkar , Zhaoqi Li

We consider the regret minimization task in a dueling bandits problem with context information. In every round of the sequential decision problem, the learner makes a context-dependent selection of two choice alternatives (arms) to be…

Machine Learning · Computer Science 2022-10-14 Viktor Bengs , Aadirupa Saha , Eyke Hüllermeier

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

Meta-learning is characterized by its ability to learn how to learn, enabling the adaptation of learning strategies across different tasks. Recent research introduced the Meta-Thompson Sampling (Meta-TS), which meta-learns an unknown prior…

Machine Learning · Statistics 2024-09-12 Hao Li , Dong Liang , Zheng Xie

In this paper, we address the contextual dueling bandit problem by proposing variance-aware algorithms that leverage neural networks to approximate nonlinear utility functions. Our approach employs a \textit{variance-aware exploration…

Machine Learning · Computer Science 2026-05-12 Youngmin Oh , Jinje Park , Taejin Paik , Jaemin Park

We consider the adversarial linear contextual bandit problem, where the loss vectors are selected fully adversarially and the per-round action set (i.e. the context) is drawn from a fixed distribution. Existing methods for this problem…

Machine Learning · Computer Science 2023-09-06 Haolin Liu , Chen-Yu Wei , Julian Zimmert

We study the stochastic linear bandit problem with multiple arms over $T$ rounds, where the covariate dimension $d$ may exceed $T$, but each arm-specific parameter vector is $s$-sparse. We begin by analyzing the sequential estimation…

Statistics Theory · Mathematics 2025-05-26 Jingyu Liu , Yanglei Song

Recent work shows that when contexts are drawn i.i.d., linear contextual bandits can be reduced to single-context linear bandits. This ``contexts are cheap" perspective is highly advantageous, as it allows for sharper finite-time analyses…

Machine Learning · Computer Science 2026-03-16 Kaan Buyukkalayci , Osama Hanna , Christina Fragouli