Anytime interval-valued outputs for kernel machines: fast support vector machine classification via distance geometry

International Conference on Machine Learning (ICML), July 2002
Anytime interval-valued outputs for kernel machines: fast support vector machine classification via distance geometry
Dennis DeCoste
Abstract

Classifying M query examples using a support vector machine containing L support vectors traditionally requires exactly M * L kernel computations.

We introduce a computational geometry method for which classification cost becomes roughly proportional to each query's difficulty (e.g. distance from the discriminant hyperplane). It produces exactly the same classifications, while typically requiring vastly fewer kernel computations.

Another publication from the same category: Machine Learning and Data Science

IEEE Computing Conference 2018, London, UK

Regularization of the Kernel Matrix via Covariance Matrix Shrinkage Estimation

The kernel trick concept, formulated as an inner product in a feature space, facilitates powerful extensions to many well-known algorithms. While the kernel matrix involves inner products in the feature space, the sample covariance matrix of the data requires outer products. Therefore, their spectral properties are tightly connected. This allows us to examine the kernel matrix through the sample covariance matrix in the feature space and vice versa. The use of kernels often involves a large number of features, compared to the number of observations. In this scenario, the sample covariance matrix is not well-conditioned nor is it necessarily invertible, mandating a solution to the problem of estimating high-dimensional covariance matrices under small sample size conditions. We tackle this problem through the use of a shrinkage estimator that offers a compromise between the sample covariance matrix and a well-conditioned matrix (also known as the "target") with the aim of minimizing the mean-squared error (MSE). We propose a distribution-free kernel matrix regularization approach that is tuned directly from the kernel matrix, avoiding the need to address the feature space explicitly. Numerical simulations demonstrate that the proposed regularization is effective in classification tasks.

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