Estimating the Bayes Point Using Linear Knapsack Problems

A Bayes Point machine is a binary classifier that approximates the Bayes-optimal classifier by estimating the mean of the posterior distribution of classifier parameters. Past Bayes Point machines have overcome the intractability of this goal by using message passing techniques that approximate the posterior of the classifier parameters as a Gaussian distribution. In this paper, we investigate alternative message passing approaches that do not rely on Gaussian approximation. To make this possible, we introduce a new computational shortcut based on linear multiplechoice knapsack problems that reduces the complexity of approximating Bayes Point belief propagation messages from exponential to linear in the number of data features. Empirical tests of our approach show significant improvement in linear classification over both soft-margin SVMs and Expectation Propagation Bayes Point machines for several realworld UCI datasets. 1