# Greed meets sparsity: understanding and improving greedy coordinate descent for sparse optimization

H. Fang, Z. Fan, Y. Sun, M. P. Friedlander
Proceeding of the 22th International Conference on Artificial Intelligence and Statistics, 2020

## Abstract

We consider greedy coordinate descent (GCD) for composite problems with sparsity inducing regularizers, including 1-norm regularization and non-negative constraints. Empirical evidence strongly suggests that GCD, when initialized with the zero vector, has an implicit screening ability that usually selects at each iteration coordinates that at are nonzero at the solution. Thus, for problems with sparse solutions, GCD can converge significantly faster than randomized coordinate descent. We present an improved convergence analysis of GCD for sparse optimization, and a formal analysis of its screening properties. We also propose and analyze an improved selection rule with stronger ability to produce sparse iterates. Numerical experiments on both synthetic and real-world data support our analysis and the effectiveness of the proposed selection rule.

## BiBTeX

@misc{1912.05068,
Author = {Huang Fang and Zhenan Fan and Yifan Sun and Michael P. Friedlander},
Title = {Greed Meets Sparsity: Understanding and Improving Greedy Coordinate Descent for Sparse Optimization},
Year = {2020},
}