<p>We study the Frank–Wolfe algorithm for minimizing a differentiable function with Lipschitz continuous gradient over a compact convex set. To extend classical complexity bounds to certain non-convex functions, we focus on the class of <i>star-convex functions</i>, which retain essential geometric properties despite the lack of convexity. We establish iteration-complexity bounds of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathcal {O}(1/k)\)</EquationSource> </InlineEquation> for both the objective values and the duality gap under star-convexity, using diminishing, Armijo-type, and Lipschitz-based stepsize rules. Notably, the diminishing and Armijo strategies do not require prior knowledge of Lipschitz or curvature constants. These results demonstrate that the Frank–Wolfe method preserves optimal complexity guarantees beyond the convex setting.</p>

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Frank–wolfe algorithm for star-convex functions

  • R. Díaz Millán,
  • O. P. Ferreira,
  • J. Ugon

摘要

We study the Frank–Wolfe algorithm for minimizing a differentiable function with Lipschitz continuous gradient over a compact convex set. To extend classical complexity bounds to certain non-convex functions, we focus on the class of star-convex functions, which retain essential geometric properties despite the lack of convexity. We establish iteration-complexity bounds of \(\mathcal {O}(1/k)\) for both the objective values and the duality gap under star-convexity, using diminishing, Armijo-type, and Lipschitz-based stepsize rules. Notably, the diminishing and Armijo strategies do not require prior knowledge of Lipschitz or curvature constants. These results demonstrate that the Frank–Wolfe method preserves optimal complexity guarantees beyond the convex setting.