Last Iterate Convergence in Monotone Mean Field Games

Fuente: arXiv
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Autori principali: Isobe, Noboru, Abe, Kenshi, Ariu, Kaito
Natura: Preprint
Pubblicazione: 2024
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author Isobe, Noboru
Abe, Kenshi
Ariu, Kaito
author_facet Isobe, Noboru
Abe, Kenshi
Ariu, Kaito
contents In the Lasry--Lions framework, Mean-Field Games (MFGs) model interactions among an infinite number of agents. However, existing algorithms either require strict monotonicity or only guarantee the convergence of averaged iterates, as in Fictitious Play in continuous time. We address this gap with the following theoretical result. First, we prove that the last-iterated policy of a proximal-point (PP) update with KL regularization converges to an equilibrium of MFG under non-strict monotonicity. Second, we see that each PP update is equivalent to finding the equilibria of a KL-regularized MFG. We then prove that this equilibrium can be found using Mirror Descent (MD) with an exponential last-iterate convergence rate. Building on these insights, we propose the Approximate Proximal-Point ($\mathtt{APP}$) algorithm, which approximately implements the PP update via a small number of MD steps. Numerical experiments on standard benchmarks confirm that the $\mathtt{APP}$ algorithm reliably converges to the unregularized mean-field equilibrium without time-averaging.
format Preprint
id arxiv_https___arxiv_org_abs_2410_05127
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Last Iterate Convergence in Monotone Mean Field Games
Isobe, Noboru
Abe, Kenshi
Ariu, Kaito
Computer Science and Game Theory
Artificial Intelligence
91A16
In the Lasry--Lions framework, Mean-Field Games (MFGs) model interactions among an infinite number of agents. However, existing algorithms either require strict monotonicity or only guarantee the convergence of averaged iterates, as in Fictitious Play in continuous time. We address this gap with the following theoretical result. First, we prove that the last-iterated policy of a proximal-point (PP) update with KL regularization converges to an equilibrium of MFG under non-strict monotonicity. Second, we see that each PP update is equivalent to finding the equilibria of a KL-regularized MFG. We then prove that this equilibrium can be found using Mirror Descent (MD) with an exponential last-iterate convergence rate. Building on these insights, we propose the Approximate Proximal-Point ($\mathtt{APP}$) algorithm, which approximately implements the PP update via a small number of MD steps. Numerical experiments on standard benchmarks confirm that the $\mathtt{APP}$ algorithm reliably converges to the unregularized mean-field equilibrium without time-averaging.
title Last Iterate Convergence in Monotone Mean Field Games
topic Computer Science and Game Theory
Artificial Intelligence
91A16
url https://arxiv.org/abs/2410.05127