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arxiv: 2307.12743 · v1 · pith:2M22D3V5new · submitted 2023-07-24 · 🧮 math.OC · cs.CC· cs.NA· math.DG· math.NA

Open Problem: Polynomial linearly-convergent method for geodesically convex optimization?

classification 🧮 math.OC cs.CCcs.NAmath.DGmath.NA
keywords convexepsilonmathcalmethodalgorithmcomplexityellipsoid-likegeodesically
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Let $f \colon \mathcal{M} \to \mathbb{R}$ be a Lipschitz and geodesically convex function defined on a $d$-dimensional Riemannian manifold $\mathcal{M}$. Does there exist a first-order deterministic algorithm which (a) uses at most $O(\mathrm{poly}(d) \log(\epsilon^{-1}))$ subgradient queries to find a point with target accuracy $\epsilon$, and (b) requires only $O(\mathrm{poly}(d))$ arithmetic operations per query? In convex optimization, the classical ellipsoid method achieves this. After detailing related work, we provide an ellipsoid-like algorithm with query complexity $O(d^2 \log^2(\epsilon^{-1}))$ and per-query complexity $O(d^2)$ for the limited case where $\mathcal{M}$ has constant curvature (hemisphere or hyperbolic space). We then detail possible approaches and corresponding obstacles for designing an ellipsoid-like method for general Riemannian manifolds.

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