arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2011.12046cs.LG
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基于k-means聚类的有效稀疏计数草图

Effective and Sparse Count-Sketch via k-means clustering

Yuhan Wang, Zijian Lei, Liang Lan

摘要:

Count-sketch是一种流行的矩阵草图绘制算法,它可以在O(nnz(X))时间内生成输入数据矩阵X的草图,其中nnz(X)表示X中非零元素的数量。草图矩阵将比X小得多,同时保留其大部分属性。因此,计数草图被广泛用于解决机器学习中的高维挑战。但是,计数草图有两个主要的局限性:(1)计数草图所使用的草图矩阵是随机生成的,没有考虑X的任何内在数据属性。这种数据无关的矩阵草图绘制方法可能会产生一个坏的草图矩阵,这将导致后续机器学习任务(例如分类)的准确性低;(2)对于高度稀疏的输入数据,计数草图可能会产生一个密集的草图数据矩阵。这种密集的草图矩阵可能会使后续的机器学习任务在计算上比在原始稀疏数据X上更昂贵。为了解决这两个局限性,我们首先通过分析计数草图方法的重建误差来展示计数草图和k均值聚类之间的有趣联系。在此基础上,提出了利用k-均值聚类算法获得低维草图矩阵的方法,以减小计数草图的重建误差。此外,我们建议解决k均值聚类使用梯度下降与-L1球投影产生一个稀疏的草图矩阵。基于六个真实分类数据集的实验结果表明,该方法比传统的count-sketch算法和其他常用的矩阵绘制算法具有更高的准确率。我们的研究结果还表明,我们的方法产生一个稀疏的草图数据矩阵比其他方法,因此,我们的方法的预测成本将小于其他矩阵草图方法。

英文摘要:

Count-sketch is a popular matrix sketching algorithm that can produce a sketch of an input data matrix X in O(nnz(X))time where nnz(X) denotes the number of non-zero entries in X. The sketched matrix will be much smaller than X while preserving most of its properties. Therefore, count-sketch is widely used for addressing high-dimensionality challenge in machine learning. However, there are two main limitations of count-sketch: (1) The sketching matrix used count-sketch is generated randomly which does not consider any intrinsic data properties of X. This data-oblivious matrix sketching method could produce a bad sketched matrix which will result in low accuracy for subsequent machine learning tasks (e.g.classification); (2) For highly sparse input data, count-sketch could produce a dense sketched data matrix. This dense sketch matrix could make the subsequent machine learning tasks more computationally expensive than on the original sparse data X. To address these two limitations, we first show an interesting connection between count-sketch and k-means clustering by analyzing the reconstruction error of the count-sketch method. Based on our analysis, we propose to reduce the reconstruction error of count-sketch by using k-means clustering algorithm to obtain the low-dimensional sketched matrix. In addition, we propose to solve k-mean clustering using gradient descent with -L1 ball projection to produce a sparse sketched matrix. Our experimental results based on six real-life classification datasets have demonstrated that our proposed method achieves higher accuracy than the original count-sketch and other popular matrix sketching algorithms. Our results also demonstrate that our method produces a sparser sketched data matrix than other methods and therefore the prediction cost of our method will be smaller than other matrix sketching methods.

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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