“…We point out that problems of the form (1.4) have been extensively studied from the viewpoint of convex programming; see, e.g., [54,12,35,30]. For example, FISTA [11] is well-known to be particularly efficient for convex problems with sparsity-enforcing 1 or TV regularizers, like R in (1.3), because proximal maps with respect to these regularizers, when iterated, can be carried out efficiently by shrinkage and TV-based denoising, respectively [35,12].…”