Fast Multidimensional Ellipsoid-Specific Fitting by Alternating Direction Method of Multipliers.

Abstract

Many problems in computer vision can be formulated as multidimensional ellipsoid-specific fitting, which is to minimize the residual error such that the underlying quadratic surface is a multidimensional ellipsoid. In this paper, we present a fast and robust algorithm for solving ellipsoid-specific fitting directly. Our method is based on the alternating direction method of multipliers, which does not introduce extra positive semi-definiteness constraints. The computation complexity is thus significantly lower than those of semi-definite programming (SDP) based methods. More specifically, to fit n data points into a p dimensional ellipsoid, our complexity is O(p(6) + np(4))+O(p(3)), where the former O results from preprocessing data once, while that of the state-of-the-art SDP method is O(p(6) + np(4) + n(3/2)p(2)) for each iteration. The storage complexity of our algorithm is about 1/2np(2), which is at most 1/4 of those of SDP methods. Extensive experiments testify to the great speed and accuracy advantages of our method over the state-of-the-art approaches. The implementation of our method is also much simpler than SDP based methods.