On the instability of local learning algorithms: Q-learning can fail in infinite state spaces

Fuente: arXiv
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Auteurs principaux: Ayesta, Urtzi, Foss, Sergey, Jonckheere, Matthieu, Puricelli, Vittorio
Format: Preprint
Publié: 2025
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author Ayesta, Urtzi
Foss, Sergey
Jonckheere, Matthieu
Puricelli, Vittorio
author_facet Ayesta, Urtzi
Foss, Sergey
Jonckheere, Matthieu
Puricelli, Vittorio
contents We investigate the challenges of applying model-free reinforcement learning algorithms, like online Q-learning, to infinite state space Markov Decision Processes (MDPs). We first introduce the notion of Local Learning Processes (LLPs), where agents make decisions based solely on local information, and we show that Q-learning can be seen as a specific instance of an LLP. Using renewal techniques, we analyze LLPs and demonstrate their instability under certain drift and initial conditions, revealing fundamental limitations in infinite state spaces. In particular, we show that while asymptotically optimal in finite settings, Q-learning can face instability and strict sub-optimality in infinite spaces. Our findings are illustrated through queueing system examples drawn from load balancing and server allocation. The study underscores the need for new theoretical frameworks and suggests future research into nonlocal Q-learning variants.
format Preprint
id arxiv_https___arxiv_org_abs_2510_25572
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the instability of local learning algorithms: Q-learning can fail in infinite state spaces
Ayesta, Urtzi
Foss, Sergey
Jonckheere, Matthieu
Puricelli, Vittorio
Probability
We investigate the challenges of applying model-free reinforcement learning algorithms, like online Q-learning, to infinite state space Markov Decision Processes (MDPs). We first introduce the notion of Local Learning Processes (LLPs), where agents make decisions based solely on local information, and we show that Q-learning can be seen as a specific instance of an LLP. Using renewal techniques, we analyze LLPs and demonstrate their instability under certain drift and initial conditions, revealing fundamental limitations in infinite state spaces. In particular, we show that while asymptotically optimal in finite settings, Q-learning can face instability and strict sub-optimality in infinite spaces. Our findings are illustrated through queueing system examples drawn from load balancing and server allocation. The study underscores the need for new theoretical frameworks and suggests future research into nonlocal Q-learning variants.
title On the instability of local learning algorithms: Q-learning can fail in infinite state spaces
topic Probability
url https://arxiv.org/abs/2510.25572