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We study online reinforcement learning in linear Markov decision processes with adversarial losses and bandit feedback, without prior knowledge on transitions or access to simulators. We introduce two algorithms that achieve improved regret…

Machine Learning · Computer Science 2023-10-19 Haolin Liu , Chen-Yu Wei , Julian Zimmert

We introduce a new algorithm for online linear-quadratic control in a known system subject to adversarial disturbances. Existing regret bounds for this setting scale as $\sqrt{T}$ unless strong stochastic assumptions are imposed on the…

Machine Learning · Computer Science 2020-06-24 Dylan J. Foster , Max Simchowitz

Motivated by alternating learning dynamics in two-player games, a recent work by Cevher et al.(2024) shows that $o(\sqrt{T})$ alternating regret is possible for any $T$-round adversarial Online Linear Optimization (OLO) problem, and left as…

Machine Learning · Computer Science 2025-06-19 Soumita Hait , Ping Li , Haipeng Luo , Mengxiao Zhang

Reverse Kullback-Leibler (KL) divergence-based regularization with respect to a fixed reference policy is widely used in modern reinforcement learning to preserve the desired traits of the reference policy and sometimes to promote…

Machine Learning · Computer Science 2026-02-05 Anupam Nayak , Tong Yang , Osman Yagan , Gauri Joshi , Yuejie Chi

Zero-sum games arise in a wide variety of problems, including robust optimization and adversarial learning. However, algorithms deployed for finding a local Nash equilibrium in these games often converge to non-Nash stationary points. This…

Computer Science and Game Theory · Computer Science 2025-09-30 Kushagra Gupta , Xinjie Liu , Ross Allen , Ufuk Topcu , David Fridovich-Keil

We revisit the problem of solving two-player zero-sum games in the decentralized setting. We propose a simple algorithmic framework that simultaneously achieves the best rates for honest regret as well as adversarial regret, and in addition…

Computer Science and Game Theory · Computer Science 2018-06-07 Ehsan Asadi Kangarshahi , Ya-Ping Hsieh , Mehmet Fatih Sahin , Volkan Cevher

We study a stochastic differential game with $N$ competitive players in a linear-quadratic framework with ergodic cost, where $d$-dimensional diffusion processes govern the state dynamics with an unknown common drift (matrix). Assuming a…

Optimization and Control · Mathematics 2026-01-30 Asaf Cohen , Ruolan He , Yuqiong Wang

Recently a multi-agent variant of the classical multi-armed bandit was proposed to tackle fairness issues in online learning. Inspired by a long line of work in social choice and economics, the goal is to optimize the Nash social welfare…

Machine Learning · Computer Science 2022-09-27 Matthew Jones , Huy Lê Nguyen , Thy Nguyen

Characterizing the performance of no-regret dynamics in multi-player games is a foundational problem at the interface of online learning and game theory. Recent results have revealed that when all players adopt specific learning algorithms,…

Computer Science and Game Theory · Computer Science 2023-11-28 Ioannis Anagnostides , Alkis Kalavasis , Tuomas Sandholm , Manolis Zampetakis

We consider the use of no-regret algorithms to compute equilibria for particular classes of convex-concave games. While standard regret bounds would lead to convergence rates on the order of $O(T^{-1/2})$, recent work \citep{RS13,SALS15}…

Machine Learning · Computer Science 2018-05-18 Jacob Abernethy , Kevin A. Lai , Kfir Y. Levy , Jun-Kun Wang

We study online learning in two-player uninformed Markov games, where the opponent's actions and policies are unobserved. In this setting, Tian et al. (2021) show that achieving no-external-regret is impossible without incurring an…

Machine Learning · Computer Science 2026-02-10 Junyan Liu , Haipeng Luo , Zihan Zhang , Lillian J. Ratliff

In this paper, we first devise two algorithms to determine whether or not a bimatrix game has a strategically equivalent zero-sum game. If so, we propose an algorithm that computes the strategically equivalent zero-sum game. If a given…

Computer Science and Game Theory · Computer Science 2021-08-12 Jianzong Pi , Joseph L. Heyman , Abhishek Gupta

Existing online learning algorithms for adversarial Markov Decision Processes achieve ${O}(\sqrt{T})$ regret after $T$ rounds of interactions even if the loss functions are chosen arbitrarily by an adversary, with the caveat that the…

Machine Learning · Computer Science 2023-10-27 Tiancheng Jin , Junyan Liu , Chloé Rouyer , William Chang , Chen-Yu Wei , Haipeng Luo

We extend the classic regret minimization framework for approximating equilibria in normal-form games by greedily weighing iterates based on regrets observed at runtime. Theoretically, our method retains all previous convergence rate…

Computer Science and Game Theory · Computer Science 2022-04-12 Hugh Zhang , Adam Lerer , Noam Brown

We introduce an online learning algorithm in the bandit feedback model that, once adopted by all agents of a congestion game, results in game-dynamics that converge to an $\epsilon$-approximate Nash Equilibrium in a polynomial number of…

Computer Science and Game Theory · Computer Science 2024-01-19 Leello Dadi , Ioannis Panageas , Stratis Skoulakis , Luca Viano , Volkan Cevher

This paper investigates the sublinear regret guarantees of two non-no-regret algorithms in zero-sum games: Fictitious Play, and Online Gradient Descent with constant stepsizes. In general adversarial online learning settings, both…

Machine Learning · Computer Science 2025-06-17 John Lazarsfeld , Georgios Piliouras , Ryann Sim , Andre Wibisono

Regret-based algorithms are highly efficient at finding approximate Nash equilibria in sequential games such as poker games. However, most regret-based algorithms, including counterfactual regret minimization (CFR) and its variants, rely on…

Machine Learning · Computer Science 2021-10-28 Chung-Wei Lee , Christian Kroer , Haipeng Luo

We introduce Q-Nash, a quantum annealing algorithm for the NP-complete problem of Fnding pure Nash equilibria in graphical games. The algorithm consists of two phases. The first phase determines all combinations of best response strategies…

Computer Science and Game Theory · Computer Science 2020-08-21 Christoph Roch , Thomy Phan , Sebastian Feld , Robert Müller , Thomas Gabor , Claudia Linnhoff-Popien

We consider a family of learning strategies for online optimization problems that evolve in continuous time and we show that they lead to no regret. From a more traditional, discrete-time viewpoint, this continuous-time approach allows us…

Optimization and Control · Mathematics 2014-02-28 Joon Kwon , Panayotis Mertikopoulos

We consider the problem of online combinatorial optimization under semi-bandit feedback, where a learner has to repeatedly pick actions from a combinatorial decision set in order to minimize the total losses associated with its decisions.…

Machine Learning · Computer Science 2015-06-11 Gergely Neu