Abstract
This paper aims to develop new and fast algorithms for recovering a sparse vector from a small number of measurements, which is a fundamental problem in the field of compressive sensing (CS). Currently, CS favors incoherent systems, in which any two measurements are as little correlated as possible. In reality, however, many problems are coherent, and conventional methods such as \(L_1\) minimization do not work well. Recently, the difference of the \(L_1\) and \(L_2\) norms, denoted as \(L_1\)–\(L_2\), is shown to have superior performance over the classic \(L_1\) method, but it is computationally expensive. We derive an analytical solution for the proximal operator of the \(L_1\)–\(L_2\) metric, and it makes some fast \(L_1\) solvers such as forward–backward splitting (FBS) and alternating direction method of multipliers (ADMM) applicable for \(L_1\)–\(L_2\). We describe in details how to incorporate the proximal operator into FBS and ADMM and show that the resulting algorithms are convergent under mild conditions. Both algorithms are shown to be much more efficient than the original implementation of \(L_1\)–\(L_2\) based on a difference-of-convex approach in the numerical experiments.
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Notes
If POCS does not converge, we discard this trial in the analysis.
We use the author’s Matlab implementation with default parameter settings and the same stopping condition adopted as \(L_1\)–\(L_2\) in the comparsion.
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Acknowledgements
The authors would like to thank Zhi Li and the anonymous reviewers for valuable comments.
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This work was partially supported by the NSF grants DMS-1522786 and DMS-1621798.
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Lou, Y., Yan, M. Fast L1–L2 Minimization via a Proximal Operator. J Sci Comput 74, 767–785 (2018). https://doi.org/10.1007/s10915-017-0463-2
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DOI: https://doi.org/10.1007/s10915-017-0463-2
Keywords
- Compressive sensing
- Proximal operator
- Forward–backward splitting
- Alternating direction method of multipliers
- Difference-of-convex