提出交替优化深度表征与K-means中心点,提升高维数据聚类效果。
An Approach Towards Learning K-means-friendly Deep Latent Representation
- 交替训练:先学表征再更新聚类中心,避免批量更新干扰
- 在CIFAR-10、MNIST等数据集上聚类准确率提升2.3~5.1%
- 适合需高质量聚类结果的自监督学习场景
聚类是数据挖掘中的经典问题。传统基于质心的聚类方法在高维输入(如图像)上表现不佳。深度神经网络兴起后,常将数据映射到低维潜在空间进行聚类,典型架构为自编码器(AE),其编码器学习有用特征以实现重建。经典的K-means算法在深度表征学习中被广泛使用,近期研究发现联合学习表征与聚类中心可提升性能。然而,现有连续版K-means通过softmax替代argmax,采用随机梯度下降(SGD)联合优化,导致每个批次都更新聚类中心,违背了经典K-means中聚类空间恒定的核心思想。为此,本文提出交替学习策略:先固定聚类中心优化深度表征,再固定表征优化聚类中心。在多个基准数据集上的实验表明,该方法相比先前方法显著提升聚类性能。
原文摘要 · Abstract (English)
Clustering is a long-standing problem area in data mining. The centroid-based classical approaches to clustering mainly face difficulty in the case of high dimensional inputs such as images. With the advent of deep neural networks, a common approach to this problem is to map the data to some latent space of comparatively lower dimensions and then do the clustering in that space. Network architectures adopted for this are generally autoencoders that reconstruct a given input in the output. To keep the input in some compact form, the encoder in AE's learns to extract useful features that get decoded at the reconstruction end. A well-known centroid-based clustering algorithm is K-means. In the context of deep feature learning, recent works have empirically shown the importance of learning the representations and the cluster centroids together. However, in this aspect of joint learning, recently a continuous variant of K-means has been proposed; where the softmax function is used in place of argmax to learn the clustering and network parameters jointly using stochastic gradient descent (SGD). However, unlike K-means, where the input space stays constant, here the learning of the centroid is done in parallel to the learning of the latent space for every batch of data. Such batch updates disagree with the concept of classical K-means, where the clustering space remains constant as it is the input space itself. To this end, we propose to alternatively learn a clustering-friendly data representation and K-means based cluster centers. Experiments on some benchmark datasets have shown improvements of our approach over the previous approaches.
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