Slingshot Perturbation to Learning in Monotone Games

This paper addresses the problem of learning Nash equilibria in {\it monotone games} where the gradient of the payoff functions is monotone in the strategy profile space, potentially containing additive noise. The optimistic family of learning algorithms, exemplified by optimistic Follow-the-Regularized-Leader and optimistic Mirror Descent, successfully achieves last-iterate convergence in scenarios devoid of noise, leading the dynamics to a Nash equilibrium. A recent emerging trend underscores the promise of the perturbation approach, where payoff functions are perturbed based on the distance from an anchoring, or {\it slingshot}, strategy. In response, we first establish a unified framework for learning equilibria in monotone games, accommodating both full and noisy feedback. Second, we construct the convergence rates toward an approximated equilibrium, irrespective of noise presence. Thirdly, we introduce a twist by updating the slingshot strategy, anchoring the current strategy at finite intervals. This innovation empowers us to identify the exact Nash equilibrium of the underlying game with guaranteed rates. The proposed framework is all-encompassing, integrating existing payoff-perturbed algorithms. Finally, empirical demonstrations affirm that our algorithms, grounded in this framework, exhibit significantly accelerated convergence.