Linear Convergence of Entropy-Regularized Natural Policy Gradient with Linear Function Approximation


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Date

2022-02-17

Publication Type

Working Paper

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Abstract

Natural policy gradient (NPG) methods with entropy regularization achieve impressive empirical success in reinforcement learning problems with large state-action spaces. However, their convergence properties and the impact of entropy regularization remain elusive in the function approximation regime. In this paper, we establish finite-time convergence analyses of entropy-regularized NPG with linear function approximation under softmax parameterization. In particular, we prove that entropy-regularized NPG with averaging satisfies the \emph{persistence of excitation} condition, and achieves a fast convergence rate of $\tilde{O}(1/T)$ up to a function approximation error in regularized Markov decision processes. This convergence result does not require any a priori assumptions on the policies. Furthermore, under mild regularity conditions on the concentrability coefficient and basis vectors, we prove that entropy-regularized NPG exhibits \emph{linear convergence} up to a function approximation error.

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published

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Pages / Article No.

2106.04096v3

Publisher

Cornell University

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Edition / version

3

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Subject

Machine Learning (cs.LG); Optimization and Control (math.OC); Machine Learning (stat.ML); FOS: Computer and information sciences; FOS: Mathematics

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09729 - He, Niao / He, Niao check_circle

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