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ETNA - Electronic Transactions on Numerical Analysis
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Verlag der Österreichischen Akademie der Wissenschaften Austrian Academy of Sciences Press
A-1011 Wien, Dr. Ignaz Seipel-Platz 2
Tel. +43-1-515 81/DW 3420, Fax +43-1-515 81/DW 3400 https://verlag.oeaw.ac.at, e-mail: verlag@oeaw.ac.at |
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DATUM, UNTERSCHRIFT / DATE, SIGNATURE
BANK AUSTRIA CREDITANSTALT, WIEN (IBAN AT04 1100 0006 2280 0100, BIC BKAUATWW), DEUTSCHE BANK MÜNCHEN (IBAN DE16 7007 0024 0238 8270 00, BIC DEUTDEDBMUC)
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ETNA - Electronic Transactions on Numerical Analysis, pp. 509-552, 2020/09/23
We develop block structure-adapted primal-dual algorithms for non-convexnon-smooth optimisation problems, whose objectives can be written as compositions$G(x)+F(K(x))$ of non-smooth block-separable convex functions $G$ and $F$ with anonlinear Lipschitz-differentiable operator $K$. Our methods are refinements ofthe nonlinear primal-dual proximal splitting method for such problems withoutthe block structure, which itself is based on the primal-dual proximal splittingmethod of Chambolle and Pock for convex problems. We propose individual steplength parameters and acceleration rules for each of the primal and dual blocksof the problem. This allows them to convergence faster by adapting to thestructure of the problem. For the squared distance of the iterates to a criticalpoint, we show local $O(1/N)$, $O(1/N^2)$, and linear rates under varyingconditions and choices of the step length parameters. Finally, we demonstrate the performance of the methods for the practical inverseproblems of diffusion tensor imaging and electrical impedance tomography.
Keywords: primal-dual algorithms, convex optimization, non-smooth optimization, step length