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The standard contextual bandit framework assumes fully observable and actionable contexts. In this work, we consider a new bandit setting with partially observable, correlated contexts and linear payoffs, motivated by the applications in…

Machine Learning · Computer Science 2024-09-19 Sihan Zeng , Sujay Bhatt , Alec Koppel , Sumitra Ganesh

The linear contextual bandit literature is mostly focused on the design of efficient learning algorithms for a given representation. However, a contextual bandit problem may admit multiple linear representations, each one with different…

Machine Learning · Computer Science 2021-04-09 Matteo Papini , Andrea Tirinzoni , Marcello Restelli , Alessandro Lazaric , Matteo Pirotta

We study the $K$-armed contextual dueling bandit problem, a sequential decision making setting in which the learner uses contextual information to make two decisions, but only observes \emph{preference-based feedback} suggesting that one…

Machine Learning · Computer Science 2021-11-25 Aadirupa Saha , Akshay Krishnamurthy

Most contextual bandit algorithms minimize regret against the best fixed policy, a questionable benchmark for non-stationary environments that are ubiquitous in applications. In this work, we develop several efficient contextual bandit…

Machine Learning · Computer Science 2019-04-05 Haipeng Luo , Chen-Yu Wei , Alekh Agarwal , John Langford

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

In this paper we consider the contextual multi-armed bandit problem for linear payoffs under a risk-averse criterion. At each round, contexts are revealed for each arm, and the decision maker chooses one arm to pull and receives the…

Machine Learning · Computer Science 2022-06-28 Yifan Lin , Yuhao Wang , Enlu Zhou

Contextual bandit algorithms are increasingly replacing non-adaptive A/B tests in e-commerce, healthcare, and policymaking because they can both improve outcomes for study participants and increase the chance of identifying good or even…

Machine Learning · Statistics 2021-06-02 Aurélien Bibaut , Antoine Chambaz , Maria Dimakopoulou , Nathan Kallus , Mark van der Laan

Linear contextual bandit is an important class of sequential decision making problems with a wide range of applications to recommender systems, online advertising, healthcare, and many other machine learning related tasks. While there is a…

Machine Learning · Statistics 2021-01-28 Yingkai Li , Yining Wang , Xi Chen , Yuan Zhou

Contextual bandits have the same exploration-exploitation trade-off as standard multi-armed bandits. On adding positive externalities that decay with time, this problem becomes much more difficult as wrong decisions at the start are hard to…

Machine Learning · Computer Science 2019-11-15 Harsh Deshpande , Vishal Jain , Sharayu Moharir

Contextual bandits algorithms aim to choose the optimal arm with the highest reward out of a set of candidates based on the contextual information. Various bandit algorithms have been applied to real-world applications due to their ability…

Machine Learning · Computer Science 2023-08-22 Yunzhe Qi , Yikun Ban , Jingrui He

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

We introduce Conformal Bandits, a novel framework integrating Conformal Prediction (CP) into bandit problems, a classic paradigm for sequential decision-making under uncertainty. Traditional regret-minimisation bandit strategies like…

Machine Learning · Computer Science 2025-12-11 Simone Cuonzo , Nina Deliu

Typical contextual bandit algorithms assume that the rewards at each round lie in some fixed range $[0, R]$, and their regret scales polynomially with this reward range $R$. However, many practical scenarios naturally involve heavy-tailed…

Machine Learning · Statistics 2025-02-05 Chenlu Ye , Yujia Jin , Alekh Agarwal , Tong Zhang

We consider the contextual bandit problem where at each time, the agent only has access to a noisy version of the context and the error variance (or an estimator of this variance). This setting is motivated by a wide range of applications…

Machine Learning · Statistics 2024-03-19 Yongyi Guo , Ziping Xu , Susan Murphy

This study investigates the problem of $K$-armed linear contextual bandits, an instance of the multi-armed bandit problem, under an adversarial corruption. At each round, a decision-maker observes an independent and identically distributed…

Machine Learning · Computer Science 2023-12-29 Masahiro Kato , Shinji Ito

Motivated by online recommendation and advertising systems, we consider a causal model for stochastic contextual bandits with a latent low-dimensional confounder. In our model, there are $L$ observed contexts and $K$ arms of the bandit. The…

Machine Learning · Computer Science 2016-10-28 Rajat Sen , Karthikeyan Shanmugam , Murat Kocaoglu , Alexandros G. Dimakis , Sanjay Shakkottai

Contextual bandit algorithms are extremely popular and widely used in recommendation systems to provide online personalised recommendations. A recurrent assumption is the stationarity of the reward function, which is rather unrealistic in…

Machine Learning · Statistics 2020-04-29 Giuseppe Di Benedetto , Vito Bellini , Giovanni Zappella

The growing interest in complex decision-making and language modeling problems highlights the importance of sample-efficient learning over very long horizons. This work takes a step in this direction by investigating contextual linear…

Machine Learning · Computer Science 2023-02-07 Yuzhen Qin , Yingcong Li , Fabio Pasqualetti , Maryam Fazel , Samet Oymak

Computationally efficient contextual bandits are often based on estimating a predictive model of rewards given contexts and arms using past data. However, when the reward model is not well-specified, the bandit algorithm may incur…

Machine Learning · Computer Science 2021-06-14 Sanath Kumar Krishnamurthy , Vitor Hadad , Susan Athey

In the dynamic landscape of online businesses, recommender systems are pivotal in enhancing user experiences. While traditional approaches have relied on static supervised learning, the quest for adaptive, user-centric recommendations has…

Information Retrieval · Computer Science 2023-12-22 Yikun Ban , Yunzhe Qi , Jingrui He