提出新型归一化误差反馈算法,实现分布式非凸优化的稳定高效训练。
Error Feedback under $(L_0,L_1)$-Smoothness: Normalization and Momentum
- 引入归一化机制,突破传统平滑性假设限制。
- 在无数据异构条件下实现O(1/√K)收敛率,步长可独立调参。
- 适用于深度网络训练,相比原算法显著提升性能。
我们首次证明了归一化误差反馈算法在广泛机器学习问题中的收敛性。尽管该类算法在训练深度神经网络中广受欢迎且高效,但其传统分析依赖于无法刻画实际目标函数特性的光滑性假设。近年来研究表明,这些任务满足广义光滑性条件,而误差反馈算法在此类条件下的理论研究仍不充分。现有分析要么局限于单节点设置,要么在分布式场景中作出过强假设,如要求数据异构或梯度噪声方差几乎必然有界。本文提出的分布式误差反馈算法通过归一化设计,在广义光滑性下实现了非凸问题的O(1/√K)收敛率,无需数据异构假设,且支持与问题参数无关的步长调整。同时,我们在随机设置下提供了强收敛保证。实验表明,由于允许更大的步长,新算法在多项式函数优化、逻辑回归和ResNet-20训练等任务中均优于非归一化版本。
原文摘要 · Abstract (English)
We provide the first proof of convergence for normalized error feedback algorithms across a wide range of machine learning problems. Despite their popularity and efficiency in training deep neural networks, traditional analyses of error feedback algorithms rely on the smoothness assumption that does not capture the properties of objective functions in these problems. Rather, these problems have recently been shown to satisfy generalized smoothness assumptions, and the theoretical understanding of error feedback algorithms under these assumptions remains largely unexplored. Moreover, to the best of our knowledge, all existing analyses under generalized smoothness either i) focus on single-node settings or ii) make unrealistically strong assumptions for distributed settings, such as requiring data heterogeneity, and almost surely bounded stochastic gradient noise variance. In this paper, we propose distributed error feedback algorithms that utilize normalization to achieve the $O(1/\sqrt{K})$ convergence rate for nonconvex problems under generalized smoothness. Our analyses apply for distributed settings without data heterogeneity conditions, and enable stepsize tuning that is independent of problem parameters. Additionally, we provide strong convergence guarantees of normalized error feedback algorithms for stochastic settings. Finally, we show that due to their larger allowable stepsizes, our new normalized error feedback algorithms outperform their non-normalized counterparts on various tasks, including the minimization of polynomial functions, logistic regression, and ResNet-20 training.
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