A trust region algorithm with a worst-case iteration complexity of O(ϵ-3/2) for nonconvex optimization

We propose a trust region algorithm for solving nonconvex smooth optimization problems. For any ϵ ¯ ∈ ( 0 , ∞ ) , the algorithm requires at most O ( ϵ - 3 / 2 ) iterations, function evaluations, and derivative evaluations to drive the norm of the gradient of the objective function below any ϵ ∈ ( 0...

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Published in:Mathematical programming Vol. 162; no. 1-2; pp. 1 - 32
Main Authors: Curtis, Frank E., Robinson, Daniel P., Samadi, Mohammadreza
Format: Journal Article
Language:English
Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2017
Springer Nature B.V
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ISSN:0025-5610, 1436-4646
Online Access:Get full text
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Summary:We propose a trust region algorithm for solving nonconvex smooth optimization problems. For any ϵ ¯ ∈ ( 0 , ∞ ) , the algorithm requires at most O ( ϵ - 3 / 2 ) iterations, function evaluations, and derivative evaluations to drive the norm of the gradient of the objective function below any ϵ ∈ ( 0 , ϵ ¯ ] . This improves upon the O ( ϵ - 2 ) bound known to hold for some other trust region algorithms and matches the O ( ϵ - 3 / 2 ) bound for the recently proposed Adaptive Regularisation framework using Cubics, also known as the arc algorithm. Our algorithm, entitled trace , follows a trust region framework, but employs modified step acceptance criteria and a novel trust region update mechanism that allow the algorithm to achieve such a worst-case global complexity bound. Importantly, we prove that our algorithm also attains global and fast local convergence guarantees under similar assumptions as for other trust region algorithms. We also prove a worst-case upper bound on the number of iterations, function evaluations, and derivative evaluations that the algorithm requires to obtain an approximate second-order stationary point.
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ISSN:0025-5610
1436-4646
DOI:10.1007/s10107-016-1026-2