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arXiv 2106.05445math.OCcs.LG
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全局利用拟牛顿法的局部收敛性:自适应样本量方法

Exploiting Local Convergence of Quasi-Newton Methods Globally: Adaptive Sample Size Approach

The University of Texas at Austin(德克萨斯大学奥斯汀分校)

Qiujiang Jin, Aryan Mokhtari

摘要:

本文研究了拟牛顿法在求解大型数据集上的经验风险最小化问题中的应用。传统的确定性和随机拟牛顿法可以用来解决这类问题,然而,众所周知,它们的整体收敛速度可能并不比一阶方法好,并且它们的局部超线性收敛只出现在学习过程的末尾。在本文中,我们使用自适应样本量计划,利用拟牛顿法的超线性收敛的全球和整个学习过程。提出的自适应样本量算法的主要思想是从一个小的数据点子集开始,在其统计精度范围内求解其对应的ERM问题,然后几何地扩大样本量,并使用较小集合对应的问题的最优解作为初始点来求解后续的具有更多样本的ERM问题。我们表明,如果初始的样本量是足够大的,我们使用拟牛顿法来解决每个子问题,子问题可以解决超线性快速(最多三次迭代后),因为我们保证迭代总是停留在一个邻域内,拟牛顿法超线性收敛。不同数据集上的数值实验证实了我们的理论结果,并证明了我们的方法的计算优势。

英文摘要:

In this paper, we study the application of quasi-Newton methods for solving empirical risk minimization (ERM) problems defined over a large dataset. Traditional deterministic and stochastic quasi-Newton methods can be executed to solve such problems; however, it is known that their global convergence rate may not be better than first-order methods, and their local superlinear convergence only appears towards the end of the learning process. In this paper, we use an adaptive sample size scheme that exploits the superlinear convergence of quasi-Newton methods globally and throughout the entire learning process. The main idea of the proposed adaptive sample size algorithms is to start with a small subset of data points and solve their corresponding ERM problem within its statistical accuracy, and then enlarge the sample size geometrically and use the optimal solution of the problem corresponding to the smaller set as an initial point for solving the subsequent ERM problem with more samples. We show that if the initial sample size is sufficiently large and we use quasi-Newton methods to solve each subproblem, the subproblems can be solved superlinearly fast (after at most three iterations), as we guarantee that the iterates always stay within a neighborhood that quasi-Newton methods converge superlinearly. Numerical experiments on various datasets confirm our theoretical results and demonstrate the computational advantages of our method.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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