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

arXiv: https://arxiv.org/abs/2603.02095 · HTML: https://mlsanity.com/paper/2603.02095/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Builds on 17 of its 21 references that are in the map.
- First posted on arXiv 2 Mar 2026.

## Builds on (most cited first, 17 of 17)

- [Intriguing properties of neural networks](https://mlsanity.com/paper/1312.6199/) (2013)
- [Delving Deep into Rectifiers: Surpassing Human-Level Performance on ImageNet Classification](https://mlsanity.com/paper/1502.01852/) (2015)
- [Evasion Attacks against Machine Learning at Test Time](https://mlsanity.com/paper/1708.06131/) (2017)
- [The Implicit Bias of Gradient Descent on Separable Data](https://mlsanity.com/paper/1710.10345/) (2017)
- [Gradient Descent Maximizes the Margin of Homogeneous Neural Networks](https://mlsanity.com/paper/1906.05890/) (2019)
- [Directional convergence and alignment in deep learning](https://mlsanity.com/paper/2006.06657/) (2020)
- [Convergence of Gradient Descent on Separable Data](https://mlsanity.com/paper/1803.01905/) (2018)
- [Risk and parameter convergence of logistic regression](https://mlsanity.com/paper/1803.07300/) (2018)
- [Gradient Descent on Two-layer Nets: Margin Maximization and Simplicity Bias](https://mlsanity.com/paper/2110.13905/) (2021)
- [Stochastic Gradient Descent on Separable Data: Exact Convergence with a Fixed Learning Rate](https://mlsanity.com/paper/1806.01796/) (2018)
- [Implicit Bias in Leaky ReLU Networks Trained on High-Dimensional Data](https://mlsanity.com/paper/2210.07082/) (2022)
- [Continuous vs. Discrete Optimization of Deep Neural Networks](https://mlsanity.com/paper/2107.06608/) (2021)
- [Fast Margin Maximization via Dual Acceleration](https://mlsanity.com/paper/2107.00595/) (2021)
- [The Double-Edged Sword of Implicit Bias: Generalization vs. Robustness in ReLU Networks](https://mlsanity.com/paper/2303.01456/) (2023)
- [Towards Understanding Learning in Neural Networks with Linear Teachers](https://mlsanity.com/paper/2101.02533/) (2021)
- [Adversarial Examples Exist in Two-Layer ReLU Networks for Low Dimensional Linear Subspaces](https://mlsanity.com/paper/2303.00783/) (2023)
- [Achieving Margin Maximization Exponentially Fast via Progressive Norm Rescaling](https://mlsanity.com/paper/2311.14387/) (2023)

## Abstract (arXiv)

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 Theta(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.