We develop subgradient- and gradient-based methods for minimizing strongly convex functions under a notion which generalizes the standard Euclidean strong convexity. We propose a unifying framework for subgradient methods which yields two kinds of methods, namely, the Proximal Gradient Method (PGM) and the Conditional Gradient Method (CGM), unifying several existing methods. The unifying framework provides tools to analyze the convergence of PGMs and CGMs for non-smooth, (weakly) smooth, and further for structured problems such as the inexact oracle models. The proposed subgradient methods yield optimal PGMs for several classes of problems and yield optimal and nearly optimal CGMs for smooth and weakly smooth problems, respectively.
Research Report B-479, Department of Mathematical and Computing Sciences, Tokyo Institute of Technology, April 2015