Abstract

Kernel approximation using random feature maps has recently gained a lot of interest. This is mainly due to their applications in reducing training and testing times of kernel based learning algorithms. In this work, we identify that previous approaches for polynomial kernel approximation create maps that can be rank deficient, and therefore may not utilize the capacity of the projected feature space effectively. To address this challenge, we propose compact random feature maps (CRAFTMaps) to approximate polynomial kernels more concisely and accurately. We prove the error bounds of CRAFTMaps demonstrating their superior kernel reconstruction performance compared to the previous approximation schemes. We show how structured random matrices can be used to efficiently generate CRAFTMaps, and present a single-pass algorithm using CRAFTMaps to learn non-linear multi-class classifiers. We present experiments on multiple standard data-sets with performance competitive with state-of-the-art results.