Nonlinear Equilibrium Transitions in a Potential Game Model for Federated Learning

Abstract:In federated learning (FL), a central server typically allocates training efforts to clients. However, from a market-oriented perspective, clients may independently choose their training efforts based on rational self-interest. To study this setting, we propose a potential game framework in which each client's payoff is determined by its individual effort and the rewards provided by the server. The rewards are influenced by the collective efforts of all clients and can be modulated by a reward factor. We first establish the existence of Nash equilibria (NEs) and then investigate their uniqueness in a stationary setting. We show that the NEs depend nonlinearly on the reward factor and exhibit a nonsmooth transition at a critical value, where the stationary potential loses strict curvature, leading to nonunique NEs and a jump between low-effort and high-effort branches. Furthermore, we prove the convergence of the best-response algorithm for computing NEs in our FL game. Finally, we apply the clients' rational efforts derived from the NEs to FL training with various datasets and models, thereby validating the effectiveness of the identified critical reward factor. The source code is available at this https URL

Funded by the European Union (Horizon Europe MSCA project ModConFlex, grant number 101073558). Code available at this https URL. Code DOI: https://doi.org/10.5281/zenodo.21381124

Machine Learning (cs.LG)

arXiv:2411.11793 [cs.LG]

(or arXiv:2411.11793v3 [cs.LG] for this version)

https://doi.org/10.1016/j.physd.2026.135288 DOI(s) linking to related resources