Strongly-polynomial time and validation analysis of policy gradient methods

Fuente: arXiv
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Autori principali: Ju, Caleb, Lan, Guanghui
Natura: Preprint
Pubblicazione: 2024
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author Ju, Caleb
Lan, Guanghui
author_facet Ju, Caleb
Lan, Guanghui
contents This paper proposes a novel termination criterion, termed the advantage gap function, for finite state and action Markov decision processes (MDP) and reinforcement learning (RL). By incorporating this advantage gap function into the design of step size rules and deriving a new linear rate of convergence that is independent of the stationary state distribution of the optimal policy, we demonstrate that policy gradient methods can solve MDPs in strongly-polynomial time. To the best of our knowledge, this is the first time that such strong convergence properties have been established for policy gradient methods. Moreover, in the stochastic setting, where only stochastic estimates of policy gradients are available, we show that the advantage gap function provides close approximations of the optimality gap for each individual state and exhibits a sublinear rate of convergence at every state. The advantage gap function can be easily estimated in the stochastic case, and when coupled with easily computable upper bounds on policy values, they provide a convenient way to validate the solutions generated by policy gradient methods. Therefore, our developments offer a principled and computable measure of optimality for RL, whereas current practice tends to rely on algorithm-to-algorithm or baselines comparisons with no certificate of optimality.
format Preprint
id arxiv_https___arxiv_org_abs_2409_19437
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Strongly-polynomial time and validation analysis of policy gradient methods
Ju, Caleb
Lan, Guanghui
Machine Learning
Artificial Intelligence
Data Structures and Algorithms
Optimization and Control
49K45, 49M05, 90C05, 90C26, 90C40, 90C46
This paper proposes a novel termination criterion, termed the advantage gap function, for finite state and action Markov decision processes (MDP) and reinforcement learning (RL). By incorporating this advantage gap function into the design of step size rules and deriving a new linear rate of convergence that is independent of the stationary state distribution of the optimal policy, we demonstrate that policy gradient methods can solve MDPs in strongly-polynomial time. To the best of our knowledge, this is the first time that such strong convergence properties have been established for policy gradient methods. Moreover, in the stochastic setting, where only stochastic estimates of policy gradients are available, we show that the advantage gap function provides close approximations of the optimality gap for each individual state and exhibits a sublinear rate of convergence at every state. The advantage gap function can be easily estimated in the stochastic case, and when coupled with easily computable upper bounds on policy values, they provide a convenient way to validate the solutions generated by policy gradient methods. Therefore, our developments offer a principled and computable measure of optimality for RL, whereas current practice tends to rely on algorithm-to-algorithm or baselines comparisons with no certificate of optimality.
title Strongly-polynomial time and validation analysis of policy gradient methods
topic Machine Learning
Artificial Intelligence
Data Structures and Algorithms
Optimization and Control
49K45, 49M05, 90C05, 90C26, 90C40, 90C46
url https://arxiv.org/abs/2409.19437