Convex optimization based on global lower second-order models

Doikov, Nikita;Nesterov, Yurii
(2020) , 22 pages

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Abstract
In this paper, we present new second-order algorithms for composite convex optimization, called Contracting-domain Newton methods. These algorithms are affine-invariant and based on global second-order lower approximation for the smooth component of the objective. Our approach has an interpretation both as a second-order generalization of the conditional gradient method, or as a variant of trust-region scheme. Under the assumption, that the problem domain is bounded, we prove ${\Os}(1/k^2)$ global rate of convergence in functional residual, where $k$ is the iteration counter, minimizing convex functions with Lipschitz continuous Hessian. This significantly improves the previously known bound ${\Os}(1/k)$ for this type of algorithms. Additionally, we propose a stochastic extension of our method, and present computational results for solving empirical risk minimization problem.
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Doikov, N., & Nesterov, Y. (2020). Convex optimization based on global lower second-order models (CORE Discussion Papers 2020/23). https://hdl.handle.net/2078.5/168446