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arXiv 2407.21091cs.LGmath.OC
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核支持向量机的随机共轭次梯度算法

The Stochastic Conjugate Subgradient Algorithm For Kernel Support Vector Machines

University of Southern California(南加利福尼亚大学)

Di Zhang, Suvrajeet Sen

AI总结:

本文针对核支持向量机提出随机共轭次梯度算法,通过自适应采样和参数选择与误差估计的分解,在保持可扩展性的同时提升收敛速度与优化精度。

摘要:

随机一阶(SFO)方法一直是应对众多现代机器学习(ML)挑战的基石。然而,它们的有效性日益受到质疑,尤其是在大规模应用中,经验证据表明其可能存在性能局限。为此,本文提出了一种专为核支持向量机(SVMs)设计的创新方法。与传统SFO技术相比,该方法不仅每次迭代收敛更快,而且展现出更强的可扩展性。不同于通常将核SVM构建为“一体化”二次规划(QP)的传统样本平均近似策略,我们的方法采用自适应采样。该策略以“按需”方式逐步细化近似精度。关键在于,这一思路还催生了一种基于分解的算法,有效地将参数选择与误差估计分离开来,其中误差估计针对每个数据点独立确定。为利用核矩阵的二次特性,我们引入了一种随机共轭次梯度方法。该方法保留了一阶方法的诸多优点,同时能够熟练处理SVM问题中的非线性和非光滑方面。因此,它超越了标准SFO算法在非光滑凸优化中的能力。本文对该新方法的收敛速率进行了深入分析。我们的实验结果表明,所提出的算法不仅保持了SFO方法的可扩展性,甚至可能超越之。此外,它显著提升了优化过程的速度和精度。

英文摘要:

Stochastic First-Order (SFO) methods have been a cornerstone in addressing a broad spectrum of modern machine learning (ML) challenges. However, their efficacy is increasingly questioned, especially in large-scale applications where empirical evidence indicates potential performance limitations. In response, this paper proposes an innovative method specifically designed for kernel support vector machines (SVMs). This method not only achieves faster convergence per iteration but also exhibits enhanced scalability when compared to conventional SFO techniques. Diverging from traditional sample average approximation strategies that typically frame kernel SVM as an 'all-in-one' Quadratic Program (QP), our approach adopts adaptive sampling. This strategy incrementally refines approximation accuracy on an 'as-needed' basis. Crucially, this approach also inspires a decomposition-based algorithm, effectively decomposing parameter selection from error estimation, with the latter being independently determined for each data point. To exploit the quadratic nature of the kernel matrix, we introduce a stochastic conjugate subgradient method. This method preserves many benefits of first-order approaches while adeptly handling both nonlinearity and non-smooth aspects of the SVM problem. Thus, it extends beyond the capabilities of standard SFO algorithms for non-smooth convex optimization. The convergence rate of this novel method is thoroughly analyzed within this paper. Our experimental results demonstrate that the proposed algorithm not only maintains but potentially exceeds the scalability of SFO methods. Moreover, it significantly enhances both speed and accuracy of the optimization process.

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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