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arXiv 2008.08427cs.LGstat.ML
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具有带限随机权重的浅层神经网络有多强大?

How Powerful are Shallow Neural Networks with Bandlimited Random Weights?

Zhejiang Normal University(浙江师范大学);RIKEN AIP(理化学研究所先进智能项目中心);China Jiliang University(中国计量大学);Shanghai Jiao Tong University(上海交通大学);Shanxi University(山西大学)

Ming Li, Sho Sonoda, Feilong Cao, Yu Guang Wang, Jiye Liang

AI总结:

本文研究带限随机权重的两层神经网络表达能力,利用ridgelet分析证明有界分布下随机权重网络存在非零逼近误差下界,并指出随机权重分布选择与目标函数复杂度相关。

摘要:

我们研究深度为2的带限随机神经网络的表达能力。随机网络是一种神经网络,其中隐藏层参数通过随机赋值被冻结,仅输出层参数通过损失最小化进行训练。对隐藏层使用随机权重是避免标准梯度下降学习中非凸优化的有效方法,该方法也已被近期的深度学习理论所采用。尽管神经网络是通用逼近器这一事实众所周知,但在本研究中,我们从数学上证明:当隐藏参数分布在一个有界域中时,网络可能无法达到零逼近误差。特别地,我们推导出一个新的非平凡的逼近误差下界。证明利用了ridgelet分析技术,这是一种为神经网络设计的调和分析方法。该方法受到经典信号处理中基本原理的启发,具体而言,即带宽有限的信号可能并不总能完美重建原始信号这一思想。我们通过各种仿真研究验证了理论结果,总体而言,给出了两个主要结论:(i)并非任意用于选择随机权重的分布都适合构建通用逼近器;(ii)随机权重的合适赋值是存在的,但在某种程度上与目标函数的复杂度相关联。

英文摘要:

We investigate the expressive power of depth-2 bandlimited random neural networks. A random net is a neural network where the hidden layer parameters are frozen with random assignment, and only the output layer parameters are trained by loss minimization. Using random weights for a hidden layer is an effective method to avoid non-convex optimization in standard gradient descent learning. It has also been adopted in recent deep learning theories. Despite the well-known fact that a neural network is a universal approximator, in this study, we mathematically show that when hidden parameters are distributed in a bounded domain, the network may not achieve zero approximation error. In particular, we derive a new nontrivial approximation error lower bound. The proof utilizes the technique of ridgelet analysis, a harmonic analysis method designed for neural networks. This method is inspired by fundamental principles in classical signal processing, specifically the idea that signals with limited bandwidth may not always be able to perfectly recreate the original signal. We corroborate our theoretical results with various simulation studies, and generally, two main take-home messages are offered: (i) Not any distribution for selecting random weights is feasible to build a universal approximator; (ii) A suitable assignment of random weights exists but to some degree is associated with the complexity of the target function.

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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