论文标题
$ \ ell_p $ - 回归的快速算法
Fast Algorithms for $\ell_p$-Regression
论文作者
论文摘要
储层计算是预测湍流的有力工具,其简单的架构具有处理大型系统的计算效率。然而,其实现通常需要完整的状态向量测量和系统非线性知识。我们使用非线性投影函数将系统测量扩展到高维空间,然后将其输入到储层中以获得预测。我们展示了这种储层计算网络在时空混沌系统上的应用,该系统模拟了湍流的若干特征。我们表明,使用径向基函数作为非线性投影器,即使只有部分观测并且不知道控制方程,也能稳健地捕捉复杂的系统非线性。最后,我们表明,当测量稀疏、不完整且带有噪声,甚至控制方程变得不准确时,我们的网络仍然可以产生相当准确的预测,从而为实际湍流系统的无模型预测铺平了道路。
The $\ell_p$-norm regression problem is a classic problem in optimization with wide ranging applications in machine learning and theoretical computer science. The goal is to compute $x^{\star} =\arg\min_{Ax=b}\|x\|_p^p$, where $x^{\star}\in \mathbb{R}^n, A\in \mathbb{R}^{d\times n},b \in \mathbb{R}^d$ and $d\leq n$. Efficient high-accuracy algorithms for the problem have been challenging both in theory and practice and the state of the art algorithms require $poly(p)\cdot n^{\frac{1}{2}-\frac{1}{p}}$ linear system solves for $p\geq 2$. In this paper, we provide new algorithms for $\ell_p$-regression (and a more general formulation of the problem) that obtain a high-accuracy solution in $O(p n^{\frac{(p-2)}{(3p-2)}})$ linear system solves. We further propose a new inverse maintenance procedure that speeds-up our algorithm to $\widetilde{O}(n^ω)$ total runtime, where $O(n^ω)$ denotes the running time for multiplying $n \times n$ matrices. Additionally, we give the first Iteratively Reweighted Least Squares (IRLS) algorithm that is guaranteed to converge to an optimum in a few iterations. Our IRLS algorithm has shown exceptional practical performance, beating the currently available implementations in MATLAB/CVX by 10-50x.