论文标题

通过非凸优化的重球动量快速找到良性区域

Quickly Finding a Benign Region via Heavy Ball Momentum in Non-Convex Optimization

论文作者

Wang, Jun-Kun, Abernethy, Jacob

论文摘要

Polyak在五十年前提出的重球方法是优化连续功能的一阶方法。尽管其随机对应物已在训练深网中非常流行,但几乎没有已知的功能,确定性重的重球比非凸优化的简单且经典的梯度下降算法更快。到目前为止,重球的成功已经避开了理论理解。我们的目标是解决这一差距,在目前的工作中,我们确定了两个非凸面问题,我们证明,重球动量有助于迭代进入一个更快地包含全球最佳点的良性区域。我们表明,重球表现出简单的动力学,这些动态清楚地揭示了为问题使用较大的动量参数值的好处。这些优化问题中的第一个是相位检索问题,该问题在物理科学中具有有用的应用。这些优化问题中的第二个是立方规范化的最小化,这是Nesterov-Polyak Cuticrized方法所需的关键子例程,以在一般平滑的非凸问题中找到二阶固定点。

The Heavy Ball Method, proposed by Polyak over five decades ago, is a first-order method for optimizing continuous functions. While its stochastic counterpart has proven extremely popular in training deep networks, there are almost no known functions where deterministic Heavy Ball is provably faster than the simple and classical gradient descent algorithm in non-convex optimization. The success of Heavy Ball has thus far eluded theoretical understanding. Our goal is to address this gap, and in the present work we identify two non-convex problems where we provably show that the Heavy Ball momentum helps the iterate to enter a benign region that contains a global optimal point faster. We show that Heavy Ball exhibits simple dynamics that clearly reveal the benefit of using a larger value of momentum parameter for the problems. The first of these optimization problems is the phase retrieval problem, which has useful applications in physical science. The second of these optimization problems is the cubic-regularized minimization, a critical subroutine required by Nesterov-Polyak cubic-regularized method to find second-order stationary points in general smooth non-convex problems.

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