Efficient Uncoupled Learning Dynamics with $\tilde{O}\!\left(T^{-1/4}\right)$ Last-Iterate Convergence in Bilinear Saddle-Point Problems over Convex Sets under Bandit Feedback

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Hauptverfasser: Maiti, Arnab, Zhang, Claire Jie, Jamieson, Kevin, Morgenstern, Jamie Heather, Panageas, Ioannis, Ratliff, Lillian J.
Format: Preprint
Veröffentlicht: 2026
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author Maiti, Arnab
Zhang, Claire Jie
Jamieson, Kevin
Morgenstern, Jamie Heather
Panageas, Ioannis
Ratliff, Lillian J.
author_facet Maiti, Arnab
Zhang, Claire Jie
Jamieson, Kevin
Morgenstern, Jamie Heather
Panageas, Ioannis
Ratliff, Lillian J.
contents In this paper, we study last-iterate convergence of learning algorithms in bilinear saddle-point problems, a preferable notion of convergence that captures the day-to-day behavior of learning dynamics. We focus on the challenging setting where players select actions from compact convex sets and receive only bandit feedback. Our main contribution is the design of an uncoupled learning algorithm that guarantees last-iterate convergence to the Nash equilibrium with high probability. We establish a convergence rate of $\tilde{O}(T^{-1/4})$ up to polynomial factors in problem parameters. Crucially, our proposed algorithm is computationally efficient, requiring only an efficient linear optimization oracle over the players' compact action sets. The algorithm is obtained by combining techniques from experimental design and the classic Follow-The-Regularized-Leader (FTRL) framework, with a carefully chosen regularizer function tailored to the geometry of the action set of each learner.
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publishDate 2026
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spellingShingle Efficient Uncoupled Learning Dynamics with $\tilde{O}\!\left(T^{-1/4}\right)$ Last-Iterate Convergence in Bilinear Saddle-Point Problems over Convex Sets under Bandit Feedback
Maiti, Arnab
Zhang, Claire Jie
Jamieson, Kevin
Morgenstern, Jamie Heather
Panageas, Ioannis
Ratliff, Lillian J.
Machine Learning
Computer Science and Game Theory
In this paper, we study last-iterate convergence of learning algorithms in bilinear saddle-point problems, a preferable notion of convergence that captures the day-to-day behavior of learning dynamics. We focus on the challenging setting where players select actions from compact convex sets and receive only bandit feedback. Our main contribution is the design of an uncoupled learning algorithm that guarantees last-iterate convergence to the Nash equilibrium with high probability. We establish a convergence rate of $\tilde{O}(T^{-1/4})$ up to polynomial factors in problem parameters. Crucially, our proposed algorithm is computationally efficient, requiring only an efficient linear optimization oracle over the players' compact action sets. The algorithm is obtained by combining techniques from experimental design and the classic Follow-The-Regularized-Leader (FTRL) framework, with a carefully chosen regularizer function tailored to the geometry of the action set of each learner.
title Efficient Uncoupled Learning Dynamics with $\tilde{O}\!\left(T^{-1/4}\right)$ Last-Iterate Convergence in Bilinear Saddle-Point Problems over Convex Sets under Bandit Feedback
topic Machine Learning
Computer Science and Game Theory
url https://arxiv.org/abs/2602.21436