Recently, a lot of attention has been paid to 1 regularization based methods for sparse signal reconstruction (e.g., basis pursuit denoising and compressed sensing) and feature selection (e.g., the Lasso algorithm) in signal processing, statistics, and related fields. These problems can be cast as 1 -regularized least-squares programs (LSPs), which can be reformulated as convex quadratic programs, and then solved by several standard methods such as interior-point methods, at least for small and medium size problems. In this paper, we describe a specialized interior-point method for solving large-scale 1 -regularized LSPs that uses the preconditioned conjugate gradients algorithm to compute the search direction. The interior-point method can solve large sparse problems, with a million variables and observations, in a few tens of minutes on a PC. It can efficiently solve large dense problems, that arise in sparse signal recovery with orthogonal transforms, by exploiting fast algorithms for these transforms. The method is illustrated on a magnetic resonance imaging data set.

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Compressed sensing or compressive sampling (CS) has been receiving a lot of interest as a promising method for signal recovery and sampling. CS problems can be cast as convex problems, and then solved by several standard methods such as interior-point methods, at least for small and medium size problems. In this paper we describe a specialized interiorpoint method for solving CS problems that uses a preconditioned conjugate gradient method to compute the search step. The method can efficiently solve large CS problems, by exploiting fast algorithms for the signal transforms used. The method is demonstrated with a medical resonance imaging (MRI) example.

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