Year: 2015
Type: preprint
Abstract: Motivated by the observation that a given signal $\boldsymbol{x}$ admits sparse representations in multiple dictionaries $\boldsymbolΨ_d$ but with varying levels of sparsity across dictionaries, we propose two new algorithms for the reconstruction of (approximately) sparse signals from noisy linear measurements. Our first algorithm, Co-L1, extends the well-known lasso algorithm from the L1 regularizer $\|\boldsymbol{Ψx}\|_1$ to composite regularizers of the form $\sum_d λ_d \|\boldsymbolΨ_d \boldsymbol{x}\|_1$ while self-adjusting the regularization weights $λ_d$. Our second algorithm, Co-IRW-L1, extends the well-known iteratively reweighted L1 algorithm to the same family of composite regularizers. We provide several interpretations of both algorithms: i) majorization-minimization (MM) applied to a non-convex log-sum-type penalty, ii) MM applied to an approximate $\ell_0$-type penalty, iii) MM applied to Bayesian MAP inference under a particular hierarchical prior, and iv) variational expectation-maximization (VEM) under a particular prior with deterministic unknown parameters. A detailed numerical study suggests that our proposed algorithms yield significantly improved recovery SNR when compared to their non-composite L1 and IRW-L1 counterparts.
Source: arXiv (Cornell University)
Authors: Ahmad, Rizwan, Schniter, Philip
Institution: The Ohio State University
Language: English
Subfield: Computational Mechanics
Field: Engineering
Domain: Physical Sciences
Open Access status: green
Funder: National Science Foundation
OpenAlex ID: W1860113857