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Frontiers of Information Technology & Electronic Engineering

ISSN 2095-9184 (print), ISSN 2095-9230 (online)

Block coordinate descent with time perturbation for nonconvex nonsmooth problems in real-world studies

Abstract: The era of big data in healthcare is here, and this era will significantly improve medicine and especially oncology. However, traditional machine learning algorithms need to be promoted to solve such large-scale real-world problems due to a large amount of data that needs to be analyzed and the difficulty in solving problems with nonconvex nonlinear settings. We aim to minimize the composite of a smooth nonlinear function and a block-separable nonconvex function on a large number of block variables with inequality constraints. We propose a novel parallel first-order optimization method, called asynchronous block coordinate descent with time perturbation (ATP), which adopts a time perturbation technique that escapes from saddle points and sub-optimal local points. The details of the proposed method are presented with analyses of convergence and iteration complexity properties. Experiments conducted on real-world machine learning problems validate the efficacy of our proposed method. The experimental results demonstrate that time perturbation enables ATP to escape from saddle points and sub-optimal points, providing a promising way to handle nonconvex optimization problems with inequality constraints employing asynchronous block coordinate descent. The asynchronous parallel implementation on shared memory multi-core platforms indicates that the proposed algorithm, ATP, has strong scalability.

Key words: Convergence analysis, Asynchronous block coordinate descent method, Time perturbation, Nonconvex nonsmooth optimization, Real-world study

Chinese Summary  <21> 面向真实世界研究中非凸非平滑问题的具有时间扰动的块坐标下降法

摘要:真实世界研究的大数据时代已经来临;这个时代将极大促进医学发展,尤其是肿瘤学。然而,鉴于大规模数据量的增加以及求解的目标问题具有非凸非平滑等不易求解的函数性质,传统机器学习方法不能很好解决这类新问题。我们的目标是求解一个带不等式约束的优化问题,该优化问题是由一个平滑非线性函数与大量块变量可分的非凸非平滑目标函数组合相加而得。提出一种新的并行一阶优化方法,称为带时间扰动的异步块坐标下降法(asynchronous block coordinate descent with time perturbation,ATP)。该方法采用一种从鞍点和次优局部点逃脱的时间扰动技术。通过分析收敛性和迭代复杂度特性,介绍了该方法的详细内容。针对真实世界研究机器学习问题的实验验证了本文所提方法的有效性。实验结果表明,时间扰动使ATP能从鞍点和次优点逃脱;采用异步块坐标下降法为处理具有不等式约束的非凸优化问题提供了一种可行方法。在共享内存多核平台上异步并行的实现,表明该算法具有很强可扩展性。

关键词组:收敛分析;异步块坐标下降法;时间扰动;非凸非平滑优化;真实世界研究


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DOI:

10.1631/FITEE.1900341

CLC number:

TP391

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On-line Access:

2019-11-11

Received:

2019-07-09

Revision Accepted:

2019-09-16

Crosschecked:

2019-10-25

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