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In this paper, we generalize the concept of heavy-tailed multi-armed bandits to adversarial environments, and develop robust best-of-both-worlds algorithms for heavy-tailed multi-armed bandits (MAB), where losses have $\alpha$-th…

Machine Learning · Computer Science 2022-06-14 Jiatai Huang , Yan Dai , Longbo Huang

We consider realizable contextual bandits with general function approximation, investigating how small reward variance can lead to better-than-minimax regret bounds. Unlike in minimax bounds, we show that the eluder dimension…

Machine Learning · Computer Science 2024-11-28 Zeyu Jia , Jian Qian , Alexander Rakhlin , Chen-Yu Wei

We propose a new partial-observability model for online learning problems where the learner, besides its own loss, also observes some noisy feedback about the other actions, depending on the underlying structure of the problem. We represent…

Machine Learning · Computer Science 2026-04-16 Tomáš Kocák , Gergely Neu , Michal Valko

Model-free reinforcement learning algorithms combined with value function approximation have recently achieved impressive performance in a variety of application domains. However, the theoretical understanding of such algorithms is limited,…

Machine Learning · Computer Science 2021-02-12 Botao Hao , Nevena Lazic , Yasin Abbasi-Yadkori , Pooria Joulani , Csaba Szepesvari

This paper studies the safe reinforcement learning problem formulated as an episodic finite-horizon tabular constrained Markov decision process with an unknown transition kernel and stochastic reward and cost functions. We propose a…

Machine Learning · Computer Science 2024-10-15 Kihyun Yu , Duksang Lee , William Overman , Dabeen Lee

Online learning has traditionally focused on the expected rewards. In this paper, a risk-averse online learning problem under the performance measure of the mean-variance of the rewards is studied. Both the bandit and full information…

Machine Learning · Statistics 2019-03-15 Sattar Vakili , Alexis Boukouvalas , Qing Zhao

In many real-world applications, it is hard to provide a reward signal in each step of a Reinforcement Learning (RL) process and more natural to give feedback when an episode ends. To this end, we study the recently proposed model of RL…

Machine Learning · Computer Science 2024-05-15 Asaf Cassel , Haipeng Luo , Aviv Rosenberg , Dmitry Sotnikov

In this paper, we study multi-armed bandits (MAB) and stochastic linear bandits (SLB) with heavy-tailed rewards and quantum reward oracle. Unlike the previous work on quantum bandits that assumes bounded/sub-Gaussian distributions for…

Machine Learning · Computer Science 2023-01-25 Yulian Wu , Chaowen Guan , Vaneet Aggarwal , Di Wang

We study episodic reinforcement learning with fixed reward and transition functions, but with episode-dependent admissible action sets that are observed at the start of each episode. Performance is measured by cumulative regret against the…

Machine Learning · Computer Science 2026-05-18 Zijun Chen , Zihan Zhang

We study the multi-armed bandit (MAB) problem with composite and anonymous feedback. In this model, the reward of pulling an arm spreads over a period of time (we call this period as reward interval) and the player receives partial rewards…

Machine Learning · Computer Science 2020-12-16 Siwei Wang , Haoyun Wang , Longbo Huang

We provide improved gap-dependent regret bounds for reinforcement learning in finite episodic Markov decision processes. Compared to prior work, our bounds depend on alternative definitions of gaps. These definitions are based on the…

Machine Learning · Computer Science 2021-10-27 Christoph Dann , Teodor V. Marinov , Mehryar Mohri , Julian Zimmert

Adaptive learning rate methods have been successfully applied in many fields, especially in training deep neural networks. Recent results have shown that adaptive methods with exponential increasing weights on squared past gradients (i.e.,…

Machine Learning · Computer Science 2021-01-05 Hui Zhong , Zaiyi Chen , Chuan Qin , Zai Huang , Vincent W. Zheng , Tong Xu , Enhong Chen

We consider the problem of combining and learning over a set of adversarial bandit algorithms with the goal of adaptively tracking the best one on the fly. The CORRAL algorithm of Agarwal et al. (2017) and its variants (Foster et al.,…

Machine Learning · Computer Science 2022-02-15 Haipeng Luo , Mengxiao Zhang , Peng Zhao , Zhi-Hua Zhou

Bayesian inference over the reward presents an ideal solution to the ill-posed nature of the inverse reinforcement learning problem. Unfortunately current methods generally do not scale well beyond the small tabular setting due to the need…

Machine Learning · Computer Science 2021-03-15 Alex J. Chan , Mihaela van der Schaar

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

We study the distribution of regret in stochastic multi-armed bandits and episodic reinforcement learning through a unified framework. We formalize a distributional regret bound as a probabilistic guarantee that holds uniformly over all…

Machine Learning · Computer Science 2026-05-08 Harin Lee , Min-hwan Oh

This paper considers the multi-armed bandit (MAB) problem and provides a new best-of-both-worlds (BOBW) algorithm that works nearly optimally in both stochastic and adversarial settings. In stochastic settings, some existing BOBW algorithms…

Machine Learning · Computer Science 2022-06-15 Shinji Ito , Taira Tsuchiya , Junya Honda

Adaptivity to the difficulties of a problem is a key property in sequential decision-making problems to broaden the applicability of algorithms. Follow-the-regularized-leader (FTRL) has recently emerged as one of the most promising…

Machine Learning · Computer Science 2024-02-14 Taira Tsuchiya , Shinji Ito , Junya Honda

One of the most basic problems in reinforcement learning (RL) is policy evaluation: estimating the long-term return, i.e., value function, corresponding to a given fixed policy. The celebrated Temporal Difference (TD) learning algorithm…

Machine Learning · Computer Science 2025-02-10 Sreejeet Maity , Aritra Mitra

We consider the problem of online learning in misspecified linear stochastic multi-armed bandit problems. Regret guarantees for state-of-the-art linear bandit algorithms such as Optimism in the Face of Uncertainty Linear bandit (OFUL) hold…

Machine Learning · Computer Science 2017-04-25 Avishek Ghosh , Sayak Ray Chowdhury , Aditya Gopalan