论文标题
对称的鲁棒procrustes:恒定因子近似和精确恢复
Symmetrized Robust Procrustes: Constant-Factor Approximation and Exact Recovery
论文作者
论文摘要
经典的$ \ textit {procrustes} $问题是找到一个僵化的运动(正交转换和翻译),该运动在最小二乘中最能使两个给定的点集对齐。 $ \ textIt {robust procrustes} $问题是一个重要的变体,其中使用power-1目标而不是最小二乘来改善异常值的鲁棒性。虽然最小二乘问题的最佳解决方案可以很容易地以封闭形式计算,但可以追溯到Schönemann(1966),但对于Power-1问题,尚无此类解决方案。在本文中,我们提出了一种新颖的凸放松,以解决鲁棒的问题。我们的放松享有几种理论和实用的优势:从理论上讲,我们证明我们的方法提供了$ \ sqrt {2} $ - 因子近似强大的procrustes问题,并且在适当的假设下,它准确地从Outliers污染了点数的点对应方面恢复了真正的刚性动作。在实践中,我们在合成和真正的鲁棒procrust问题的数值实验中发现,我们的方法的性能与标准迭代的最小平方(IRLS)相似。但是,我们的算法的凸度允许纳入其他凸惩罚,这不容易被IRLS。事实证明,这是一个实质性的优势,从而改善了高维问题的结果,包括非刚性形状比对和半监视的语言词翻译。
The classical $\textit{Procrustes}$ problem is to find a rigid motion (orthogonal transformation and translation) that best aligns two given point-sets in the least-squares sense. The $\textit{Robust Procrustes}$ problem is an important variant, in which a power-1 objective is used instead of least squares to improve robustness to outliers. While the optimal solution of the least-squares problem can be easily computed in closed form, dating back to Schönemann (1966), no such solution is known for the power-1 problem. In this paper we propose a novel convex relaxation for the Robust Procrustes problem. Our relaxation enjoys several theoretical and practical advantages: Theoretically, we prove that our method provides a $\sqrt{2}$-factor approximation to the Robust Procrustes problem, and that, under appropriate assumptions, it exactly recovers the true rigid motion from point correspondences contaminated by outliers. In practice, we find in numerical experiments on both synthetic and real robust Procrustes problems, that our method performs similarly to the standard Iteratively Reweighted Least Squares (IRLS). However the convexity of our algorithm allows incorporating additional convex penalties, which are not readily amenable to IRLS. This turns out to be a substantial advantage, leading to improved results in high-dimensional problems, including non-rigid shape alignment and semi-supervised interlingual word translation.