Permutation invariant SVMs

Abstract

We extend Support Vector Machines to input spaces that are sets by ensuring that the classifier is invariant to permutations of subelements within each input. Such permutations include reordering of scalars in an input vector, re-orderings of tuples in an input matrix or re-orderings of general objects (in Hubert spaces) within a set as well. This approach induces permutational invariance in the classifier which can then be directly applied to unusual set-based representations of data. The permutation invariant Support Vector Machine alternates the Hungarian method for maximum weight matching within the maximum margin learning procedure. We effectively estimate and apply permutations to the input data points to maximize classification margin while minimizing data radius. This procedure has a strong the- oretical justification via well established error probability bounds. Experiments are shown on character recognition, 3D object recognition and various UCI datasets.