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1. chinaXiv:201803.00428 [pdf]

逻辑回归上的反拉加速方法

何沧平
分类: 数学 >> 计算数学

本文通过严格数学分析找出了逻辑回归过拟合的成因:边界样本的损失贡献比重大且随法向量增长而加速增大、边界样本分布散乱,顺便理清了正则项的作用机理。 利用过拟合机制,本文提出一种反拉方法,既能缓解过拟合,又能减少训练步数,在MNIST数据集上实现加速38.25倍,在CIFAR10数据集上实现加速5.61倍。

提交时间: 2018-04-03 点击量1051下载量98 评论 0

2. chinaXiv:201803.00428 [pdf]

逻辑回归上的反拉加速方法

何沧平
分类: 数学 >> 计算数学

本文通过严格数学分析找出了逻辑回归过拟合的成因:边界样本的损失贡献比重大且随法向量增长而加速增大、边界样本分布散乱,顺便理清了正则项的作用机理。 利用过拟合机制,本文提出一种反拉方法,既能缓解过拟合,又能减少训练步数,在MNIST数据集上实现加速38.25倍,在CIFAR10数据集上实现加速5.61倍。

提交时间: 2018-03-22 点击量1395下载量446 评论 0

3. chinaXiv:201708.00246 [pdf]

From limited-aperture to full-aperture

Xiaodong Liu
分类: 数学 >> 计算数学

Many numerical methods have been proposed in the last 30 years for inverse problems. While very successful in many cases, progress has lagged in other areas of applications which are forced to rely on {\em limited-aperture} measurements. In this paper, we introduce some techniques to retrieve the other data that can not be measured directly. We consider the inverse acoustic scattering of time harmonic plane waves and take the scattering amplitude to be the measurements. Assume that the scattering amplitude can only be measured with observation directions restricted in $S^{n-1}_0$, which is compactly supported in the unit sphere. Based on the reciprocity relation of the scattering amplitude, we prove a special symmetric structure of the corresponding multi-static response matrix. This will also be verified by numerical examples. Combining this, with the help of the Green's formula for the scattered field, we introduce an iterative scheme to retrieve approximate {\em full-aperture} scattering amplitude. As an application, using a recently proposed direct sampling method [28], we consider the fast and robust sampling methods with {\em limited-aperture} measurements. Some numerical simulations are conducted with noisy data, and the results will further verify the effectiveness and robustness of the proposed data retrieval method and of the sampling method for inverse acoustic scattering problems.

提交时间: 2017-08-22 点击量1169下载量913 评论 0

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