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We study contextual bandit (CB) problems, where the user can sometimes respond with the best action in a given context. Such an interaction arises, for example, in text prediction or autocompletion settings, where a poor suggestion is…

Machine Learning · Computer Science 2023-02-09 Alekh Agarwal , Claudio Gentile , Teodor V. Marinov

We study adversarial attacks that manipulate the reward signals to control the actions chosen by a stochastic multi-armed bandit algorithm. We propose the first attack against two popular bandit algorithms: $\epsilon$-greedy and UCB,…

Machine Learning · Computer Science 2018-10-30 Kwang-Sung Jun , Lihong Li , Yuzhe Ma , Xiaojin Zhu

Contextual bandits provide an effective way to model the dynamic data problem in ML by leveraging online (incremental) learning to continuously adjust the predictions based on changing environment. We explore details on contextual bandits,…

Machine Learning · Computer Science 2020-09-24 Dattaraj Rao

Bandit learning is characterized by the tension between long-term exploration and short-term exploitation. However, as has recently been noted, in settings in which the choices of the learning algorithm correspond to important decisions…

Machine Learning · Computer Science 2018-01-11 Sampath Kannan , Jamie Morgenstern , Aaron Roth , Bo Waggoner , Zhiwei Steven Wu

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 consider a multi-armed bandit problem where payoffs are a linear function of an observed stochastic contextual variable. In the scenario where there exists a gap between optimal and suboptimal rewards, several algorithms have been…

Data Structures and Algorithms · Computer Science 2014-07-08 José Bento , Stratis Ioannidis , S. Muthukrishnan , Jinyun Yan

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

We consider the linear contextual bandit problem with resource consumption, in addition to reward generation. In each round, the outcome of pulling an arm is a reward as well as a vector of resource consumptions. The expected values of…

Machine Learning · Computer Science 2016-07-12 Shipra Agrawal , Nikhil R. Devanur

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

Contextual bandit algorithms are at the core of many applications, including recommender systems, clinical trials, and optimal portfolio selection. One of the most popular problems studied in the contextual bandit literature is to maximize…

Machine Learning · Computer Science 2023-10-24 Siddhant Chaudhary , Abhishek Sinha

This work explores the idea of a causal contextual multi-armed bandit approach to automated marketing, where we estimate and optimize the causal (incremental) effects. Focusing on causal effect leads to better return on investment (ROI) by…

Machine Learning · Computer Science 2018-10-05 Neela Sawant , Chitti Babu Namballa , Narayanan Sadagopan , Houssam Nassif

In stochastic contextual bandits, an agent sequentially makes actions from a time-dependent action set based on past experience to minimize the cumulative regret. Like many other machine learning algorithms, the performance of bandits…

Machine Learning · Computer Science 2024-04-09 Yue Kang , Cho-Jui Hsieh , Thomas C. M. Lee

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

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

We consider a contextual version of multi-armed bandit problem with global knapsack constraints. In each round, the outcome of pulling an arm is a scalar reward and a resource consumption vector, both dependent on the context, and the…

Machine Learning · Computer Science 2016-07-12 Shipra Agrawal , Nikhil R. Devanur , Lihong Li

Virtual support agents have grown in popularity as a way for businesses to provide better and more accessible customer service. Some challenges in this domain include ambiguous user queries as well as changing support topics and user…

Machine Learning · Computer Science 2021-12-07 Sandra Sajeev , Jade Huang , Nikos Karampatziakis , Matthew Hall , Sebastian Kochman , Weizhu Chen

We propose a contextual bandit based model to capture the learning and social welfare goals of a web platform in the presence of myopic users. By using payments to incentivize these agents to explore different items/recommendations, we show…

Machine Learning · Computer Science 2020-01-23 Priyank Agrawal , Theja Tulabandhula

We study "adversarial scaling", a multi-armed bandit model where rewards have a stochastic and an adversarial component. Our model captures display advertising where the "click-through-rate" can be decomposed to a (fixed across time)…

Machine Learning · Computer Science 2020-09-01 Thodoris Lykouris , Vahab Mirrokni , Renato Paes Leme

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

Contextual bandits often provide simple and effective personalization in decision making problems, making them popular tools to deliver personalized interventions in mobile health as well as other health applications. However, when bandits…

Machine Learning · Computer Science 2021-07-28 Jiayu Yao , Emma Brunskill , Weiwei Pan , Susan Murphy , Finale Doshi-Velez