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arXiv 2112.13530cs.LGmath.OCstat.ML
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Wasserstein流与复制者动态的相遇:Actor-Critic中表示学习的平均场分析

Wasserstein Flow Meets Replicator Dynamics: A Mean-Field Analysis of Representation Learning in Actor-Critic

Northwestern University(西北大学);Yale University(耶鲁大学);Princeton University(普林斯顿大学);University of California, Berkeley(加州大学伯克利分校)

Yufeng Zhang, Siyu Chen, Zhuoran Yang, Michael I. Jordan, Zhaoran Wang

AI总结:

本文从平均场角度分析过参数化两层神经Actor-Critic在双时间尺度下的表示学习演化,证明其以次线性速率收敛到全局最优策略,且critic特征表示保持在初始值邻域内。

摘要:

近年来,借助神经网络赋能的Actor-Critic(AC)算法在经验上取得了显著成功。然而,现有关于AC算法的大部分理论支持集中于线性函数逼近或线性化神经网络的情形,其中特征表示在整个训练过程中保持固定。这一局限未能捕捉神经AC中表示学习的关键方面,而表示学习在实际问题中至关重要。在本工作中,我们采用平均场视角研究基于特征的神经AC的演化与收敛。具体而言,我们考虑一种AC版本,其中actor和critic均由过参数化的两层神经网络表示,并以双时间尺度学习率进行更新。critic通过时间差分(TD)学习以较大步长更新,而actor通过近端策略优化(PPO)以较小步长更新。在连续时间与无限宽度的极限机制下,当时间尺度被适当分离时,我们证明神经AC以次线性速率找到全局最优策略。此外,我们证明由critic网络诱导的特征表示被允许在初始特征表示的邻域内演化。

英文摘要:

Actor-critic (AC) algorithms, empowered by neural networks, have had significant empirical success in recent years. However, most of the existing theoretical support for AC algorithms focuses on the case of linear function approximations, or linearized neural networks, where the feature representation is fixed throughout training. Such a limitation fails to capture the key aspect of representation learning in neural AC, which is pivotal in practical problems. In this work, we take a mean-field perspective on the evolution and convergence of feature-based neural AC. Specifically, we consider a version of AC where the actor and critic are represented by overparameterized two-layer neural networks and are updated with two-timescale learning rates. The critic is updated by temporal-difference (TD) learning with a larger stepsize while the actor is updated via proximal policy optimization (PPO) with a smaller stepsize. In the continuous-time and infinite-width limiting regime, when the timescales are properly separated, we prove that neural AC finds the globally optimal policy at a sublinear rate. Additionally, we prove that the feature representation induced by the critic network is allowed to evolve within a neighborhood of the initial one.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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