paper

Global rates of convergence for nonconvex optimization on manifolds

arXiv:1605.08101 · doi:10.1093/imanum/drx080

Abstract

We consider the minimization of a cost function on a manifold using Riemannian gradient descent and Riemannian trust regions (RTR). We focus on satisfying necessary optimality conditions within a tolerance . Specifically, we show that, under Lipschitz-type assumptions on the pullbacks of to the tangent spaces of , both of these algorithms produce points with Riemannian gradient smaller than in iterations. Furthermore, RTR returns a point where also the Riemannian Hessian's least eigenvalue is larger than in iterations. There are no assumptions on initialization. The rates match their (sharp) unconstrained counterparts as a function of the accuracy (up to constants) and hence are sharp in that sense. These are the first deterministic results for global rates of convergence to approximate first- and second-order Karush-Kuhn-Tucker points on manifolds. They apply in particular for optimization constrained to compact submanifolds of , under simpler assumptions.

33 pages, IMA Journal of Numerical Analysis, 2018

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