On the Rate of Convergence of GD in Non-linear Neural Networks: An Adversarial Robustness Perspective

Fuente: arXiv
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Autores principales: Smorodinsky, Guy, Gimpleson, Sveta, Safran, Itay
Formato: Preprint
Publicado: 2026
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author Smorodinsky, Guy
Gimpleson, Sveta
Safran, Itay
author_facet Smorodinsky, Guy
Gimpleson, Sveta
Safran, Itay
contents We study the convergence dynamics of Gradient Descent (GD) in a minimal binary classification setting, consisting of a two-neuron ReLU network and two training instances. We prove that even under these strong simplifying assumptions, while GD successfully converges to an optimal robustness margin, effectively maximizing the distance between the decision boundary and the training points, this convergence occurs at a prohibitively slow rate, scaling strictly as $Θ(1/\ln(t))$. To the best of our knowledge, this establishes the first explicit lower bound on the convergence rate of the robustness margin in a non-linear model. Through empirical simulations, we further demonstrate that this inherent failure mode is pervasive, exhibiting the exact same tight convergence rate across multiple natural network initializations. Our theoretical guarantees are derived via a rigorous analysis of the GD trajectories across the distinct activation patterns of the model. Specifically, we develop tight control over the system's dynamics to bound the trajectory of the decision boundary, overcoming the primary technical challenge introduced by the non-linear nature of the architecture.
format Preprint
id arxiv_https___arxiv_org_abs_2603_02095
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the Rate of Convergence of GD in Non-linear Neural Networks: An Adversarial Robustness Perspective
Smorodinsky, Guy
Gimpleson, Sveta
Safran, Itay
Machine Learning
Artificial Intelligence
We study the convergence dynamics of Gradient Descent (GD) in a minimal binary classification setting, consisting of a two-neuron ReLU network and two training instances. We prove that even under these strong simplifying assumptions, while GD successfully converges to an optimal robustness margin, effectively maximizing the distance between the decision boundary and the training points, this convergence occurs at a prohibitively slow rate, scaling strictly as $Θ(1/\ln(t))$. To the best of our knowledge, this establishes the first explicit lower bound on the convergence rate of the robustness margin in a non-linear model. Through empirical simulations, we further demonstrate that this inherent failure mode is pervasive, exhibiting the exact same tight convergence rate across multiple natural network initializations. Our theoretical guarantees are derived via a rigorous analysis of the GD trajectories across the distinct activation patterns of the model. Specifically, we develop tight control over the system's dynamics to bound the trajectory of the decision boundary, overcoming the primary technical challenge introduced by the non-linear nature of the architecture.
title On the Rate of Convergence of GD in Non-linear Neural Networks: An Adversarial Robustness Perspective
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2603.02095