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Personalized recommendations for new users, also known as the cold-start problem, can be formulated as a contextual bandit problem. Existing contextual bandit algorithms generally rely on features alone to capture user variability. Such…

Machine Learning · Computer Science 2016-04-25 Li Zhou , Emma Brunskill

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

In networked environments, users frequently share recommendations about content, products, services, and courses of action with others. The extent to which such recommendations are successful and adopted is highly contextual, dependent on…

Machine Learning · Computer Science 2025-10-23 Ahmed Sayeed Faruk , Mohammad Shahverdikondori , Elena Zheleva

Contextual bandits are online learners that, given an input, select an arm and receive a reward for that arm. They use the reward as a learning signal and aim to maximize the total reward over the inputs. Contextual bandits are commonly…

Machine Learning · Computer Science 2020-02-14 Awni Hannun , Brian Knott , Shubho Sengupta , Laurens van der Maaten

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

In this survey we cover a few stochastic and adversarial contextual bandit algorithms. We analyze each algorithm's assumption and regret bound.

Machine Learning · Computer Science 2016-02-02 Li Zhou

We investigate contextual bandits in the presence of side-observations across arms in order to design recommendation algorithms for users connected via social networks. Users in social networks respond to their friends' activity, and hence…

Machine Learning · Computer Science 2020-10-27 Rahul Singh , Fang Liu , Xin Liu , Ness Shroff

Contextual bandit algorithms provide principled online learning solutions to balance the exploitation-exploration trade-off in various applications such as recommender systems. However, the learning speed of the traditional contextual…

Machine Learning · Computer Science 2020-01-28 Xiaoying Zhang , Hong Xie , Hang Li , John C. S. Lui

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

Recommender systems trained in a continuous learning fashion are plagued by the feedback loop problem, also known as algorithmic bias. This causes a newly trained model to act greedily and favor items that have already been engaged by…

Machine Learning · Computer Science 2020-08-04 Dalin Guo , Sofia Ira Ktena , Ferenc Huszar , Pranay Kumar Myana , Wenzhe Shi , Alykhan Tejani

Designing efficient general-purpose contextual bandit algorithms that work with large -- or even continuous -- action spaces would facilitate application to important scenarios such as information retrieval, recommendation systems, and…

Machine Learning · Computer Science 2022-07-14 Yinglun Zhu , Paul Mineiro

We study the stream-based online active learning in a contextual multi-armed bandit framework. In this framework, the reward depends on both the arm and the context. In a stream-based active learning setting, obtaining the ground truth of…

Machine Learning · Computer Science 2016-07-13 Linqi Song

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

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

Focusing on Random Forests, we propose a multi-armed contextual bandit recommendation framework for feature-based selection of a single shallow tree of the learned ensemble. The trained system, which works on top of the Random Forest,…

Machine Learning · Statistics 2022-07-14 Tommaso Aldinucci , Enrico Civitelli , Leonardo di Gangi , Alessandro Sestini

This paper considers a contextual bandit problem involving multiple agents, where a learner sequentially observes the contexts and the agent's reported arms, and then selects the arm that maximizes the system's overall reward. Existing work…

Machine Learning · Computer Science 2025-05-30 Arun Verma , Indrajit Saha , Makoto Yokoo , Bryan Kian Hsiang Low

The contextual duelling bandit problem models adaptive recommender systems, where the algorithm presents a set of items to the user, and the user's choice reveals their preference. This setup is well suited for implicit choices users make…

Machine Learning · Computer Science 2025-08-27 Suryanarayana Sankagiri , Jalal Etesami , Pouria Fatemi , Matthias Grossglauser

We consider nonstationary multi-armed bandit problems where the model parameters of the arms change over time. We introduce the adaptive resetting bandit (ADR-bandit), a bandit algorithm class that leverages adaptive windowing techniques…

Machine Learning · Statistics 2023-10-27 Junpei Komiyama , Edouard Fouché , Junya Honda

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

Most bandit policies are designed to either minimize regret in any problem instance, making very few assumptions about the underlying environment, or in a Bayesian sense, assuming a prior distribution over environment parameters. The former…

Machine Learning · Computer Science 2021-01-07 Branislav Kveton , Martin Mladenov , Chih-Wei Hsu , Manzil Zaheer , Csaba Szepesvari , Craig Boutilier