Finding a zero of a maximalmonotoneoperator is fundamental in convex optimization and monotoneoperator theory, and proximal point algorithm (PPA) is a primary method for solving this problem. PPA converges not only...
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Finding a zero of a maximalmonotoneoperator is fundamental in convex optimization and monotoneoperator theory, and proximal point algorithm (PPA) is a primary method for solving this problem. PPA converges not only globally under fairly mild conditions but also asymptotically at a fast linear rate provided that the underlying inverse operator is Lipschitz continuous at the origin. These nice convergence properties are preserved by a relaxed variant of PPA. Recently, a linear convergence bound was established in [M. Tao, and X. M. Yuan, J. Sci. Comput., 74 (2018), pp. 826-850] for the relaxed PPA, and it was shown that the bound is tight when the relaxation factor gamma lies in [1, 2). However, for other choices of gamma, the bound obtained by Tao and Yuan is suboptimal. In this paper, we establish tight linear convergence bounds for any choice of gamma is an element of (0, 2) using a unified and much simplified analysis. These results sharpen our understandings to the asymptotic behavior of the relaxed PPA and make the whole picture for gamma is an element of (0, 2) clear.
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