Convergence of an inertial proximal method for l1-regularized least-squares

A fast, low-complexity, algorithm for solving the `1-regularized least-squares problem is devised and analyzed. Our algorithm, which we call the Inertial Iterative Soft-Thresholding Algorithm (I-ISTA), incorporates inertia into a forward-backward proximal splitting framework. We show that I-ISTA has a linear rate of convergence with a smaller asymptotic error constant than the well-known Iterative Shrinkage/Soft-Thresholding Algorithm (ISTA) for solving `1-regularized least-squares. The improvement in asymptotic error constant over ISTA is significant on ill-conditioned problems and is gained with minor additional computations. We conduct numerical experiments which show that I-ISTA converges more quickly than ISTA and two other computationally comparable algorithms on compressed sensing and deconvolution problems.