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Main Authors: Anita, Stefana-Lucia, Turinici, Gabriel
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2605.03752
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author Anita, Stefana-Lucia
Turinici, Gabriel
author_facet Anita, Stefana-Lucia
Turinici, Gabriel
contents Multi Armed Bandit (MAB) algorithms are a cornerstone of reinforcement learning and have been studied both theoretically and numerically. One of the most commonly used implementation uses a softmax mapping to prescribe the optimal policy and served as the foundation for downstream algorithms, including REINFORCE. Distinct from vanilla approaches, we consider here the L2 regularized softmax policy gradient where a quadratic term is subtracted from the mean reward. Previous studies exploiting convexity failed to identify a suitable theoretical framework to analyze its convergence when the regularization parameter vanishes. We prove here theoretical convergence results and confirm empirically that this regime makes the L2 regularization numerically advantageous on standard benchmarks.
format Preprint
id arxiv_https___arxiv_org_abs_2605_03752
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Vanishing L2 regularization for the softmax Multi Armed Bandit
Anita, Stefana-Lucia
Turinici, Gabriel
Machine Learning
Statistics Theory
68T05, 90C40, 68Q25, 90C25
F.2.2; F.1.2; I.2.6
Multi Armed Bandit (MAB) algorithms are a cornerstone of reinforcement learning and have been studied both theoretically and numerically. One of the most commonly used implementation uses a softmax mapping to prescribe the optimal policy and served as the foundation for downstream algorithms, including REINFORCE. Distinct from vanilla approaches, we consider here the L2 regularized softmax policy gradient where a quadratic term is subtracted from the mean reward. Previous studies exploiting convexity failed to identify a suitable theoretical framework to analyze its convergence when the regularization parameter vanishes. We prove here theoretical convergence results and confirm empirically that this regime makes the L2 regularization numerically advantageous on standard benchmarks.
title Vanishing L2 regularization for the softmax Multi Armed Bandit
topic Machine Learning
Statistics Theory
68T05, 90C40, 68Q25, 90C25
F.2.2; F.1.2; I.2.6
url https://arxiv.org/abs/2605.03752