提出一种利用高阶平滑性的随机优化方法,显著提升收敛速度。
A stochastic first-order method with multi-extrapolated momentum for highly smooth unconstrained optimization
- 每轮迭代进行多次外推,再通过动量更新,利用函数高阶平滑性
- 理论证明样本复杂度达 $\widetilde{\mathcal{O}}(ε^{-(3p+1)/p})$,优于已有结果
- 首次实现任意阶平滑性下的加速,适合高精度优化场景
本文研究具有高阶光滑性的无约束随机优化问题。提出一种新的随机一阶方法(SFOM),在每轮迭代中执行多次外推,随后基于这些外推结果进行动量更新。我们证明该方法可利用目标函数的高阶光滑性实现优化加速。假设目标函数 $f$ 的第 $p$ 阶导数($p\ge2$)满足Lipschitz连续,在额外温和假设下,该方法在找到满足 $\mathbb{E}[\|\nabla f(x)\|]\leε$ 的点时,达到样本复杂度 $\widetilde{\mathcal{O}}(ε^{-(3p+1)/p})$。据我们所知,这是首个利用任意阶光滑性实现加速的随机一阶方法,其复杂度优于不依赖均方光滑性假设的现有最优结果。初步数值实验验证了方法的实际性能并支持理论结论。
原文摘要 · Abstract (English)
In this paper, we consider an unconstrained stochastic optimization problem where the objective function exhibits high-order smoothness. Specifically, we propose a new stochastic first-order method (SFOM) with multi-extrapolated momentum, in which multiple extrapolations are performed in each iteration, followed by a momentum update based on these extrapolations. We demonstrate that the proposed SFOM can accelerate optimization by exploiting the high-order smoothness of the objective function $f$. Assuming that the $p$th-order derivative of $f$ is Lipschitz continuous for some $p\ge2$, and under additional mild assumptions, we establish that our method achieves a sample complexity of $\widetilde{\mathcal{O}}(ε^{-(3p+1)/p})$ for finding a point $x$ such that $\mathbb{E}[\|\nabla f(x)\|]\leε$. To the best of our knowledge, this is the first SFOM to leverage arbitrary-order smoothness of the objective function for acceleration, resulting in a sample complexity that improves upon the best-known results without assuming the mean-squared smoothness condition. Preliminary numerical experiments validate the practical performance of our method and support our theoretical findings.
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