arXiv:2605.18528math.OCcs.LG2026-05

提出可应对重尾噪声的尺度不变优化方法,提升训练效率与泛化能力。

Scale-Invariant Neural Network Optimization: Norm Geometry and Heavy-Tailed Noise

  • 设计基于谱范数的尺度不变优化器,适应网络参数化结构。
  • 理论证明在重尾噪声下需至少Ω( min{m,n} ε^{- (3p-2)/(p-1) } )梯度查询次数。
  • 引入高阶光滑性改进,实现更优收敛速度,适用于多规模模型训练。

神经网络优化中,优化器设计需考虑模型参数化方式。层间输入输出结构启发了尺度不变优化器(如Muon、Scion),其更新支持超参数迁移。同时,深度学习中的随机梯度噪声常呈重尾分布,非亚高斯。尽管已有算法原则形成,但二者联合的理论分析仍不充分。本文研究在ℝ^{m×n}上带一般范数及p-th矩重尾噪声的非凸平滑随机优化问题,目标是获得双范数下的ε-驻点。首次建立维度相关下界:当max{m,n}/(min{m,n})²较大时,任意梯度法需Ω(min{m,n} ε^{-(3p-2)/(p-1)}) oracle。证明使用谱范数的尺度不变Scion方法可达匹配上界O(min{m,n} ε^{-(3p-2)/(p-1)})。进一步提出传输式Scion方法,利用二阶光滑性(Hessian Lipschitz)将上界改进至O(min{m,n} ε^{-(5p-3)/(2p-2)})。最后结合启发式策略,在多种架构与规模模型上验证其灵活性与兼容性。

原文摘要 · Abstract (English)

A growing lesson from neural network optimization is that optimizer design should respect how the model is parametrized. The layerwise input-output structure of neural networks motivates scale-invariant optimizers, such as Muon and Scion, whose updates also support hyperparameter transfer. At the same time, stochastic gradient noise in deep learning is often far from sub-Gaussian and may exhibit heavy tails. These observations have shaped recent algorithmic principles for training neural networks, yet their joint theoretical consequences are underexplored. In particular, it remains unclear what dimension dependence is unavoidable for gradient-based methods given the problem class is defined by input-output norm and under heavy-tailed noise, and whether higher-order smoothness can accelerate training. We study these questions through nonconvex smooth stochastic optimization over $\mathbb R^{m\times n}$ equipped with general norms and under $p^\mathrm{th}$-moment heavy-tailed noise, where the goal is to achieve an $ε$-stationary point in the dual norm. Our first contribution is a dimension-dependent lower bound: when $\frac{\max\{m,n\}}{(\min\{m,n\})^2}$ is large enough, any gradient-based method requires $Ω(\min\{m, n\}ε^{-\frac{3p-2}{p-1}})$ oracles for the problem class defined by the spectral norm, which is a common input-output norm. We prove that a scale-invariant Scion method with the spectral norm can achieve the matching upper bound of $O(\min\{m, n\}ε^{-\frac{3p-2}{p-1}})$. To exploit higher-order smoothness, we propose a transported Scion method and improve the bound to $O(\min\{m, n\}ε^{-\frac{5p-3}{2p-2}})$ when the Hessian is Lipschitz. Finally, we incorporate heuristics into our transported method and evaluate it across multiple architectures and model sizes, demonstrating its flexibility and compatibility with neural network training.

优化器重尾噪声尺度不变收敛性

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