math.OCOct 2, 2026

Near-Optimal Convex Optimization with Lazy Second-Order Oracles

Authors: Xinliang Zhang, Lesi Chen, Chengchang Liu, Jingzhao Zhang

Organizations: IIIS, Tsinghua University · Department of Artificial Intelligence, Westlake University.

Abstract

This paper studies the complexity of convex optimization using lazy second-order oracles (Doikov, Chayti, and Jaggi, ICML 2023), where an algorithm queries gradients every iteration and Hessians once per mm iterations. Under this setting, we show a lower bound of Ω(m+m1/7ε−2/7)Ω(m+ m^{1/7} ε^{-2/7}) on the number of total iterations to find an εε-solution using a novel block zero-chain construction. Then we propose a novel method that achieves a new upper bound of O~(m+m1/7ε−2/7)\tilde{\mathcal{O}}(m+ m^{1/7} ε^{-2/7}), which significantly improves the prior one (Chen, Liu, Luo, and Zhang, COLT 2026) of O~(m+m13/21ε−2/7)\tilde{\mathcal{O}}(m+ m^{13/21} ε^{-2/7}) and is tight up to logarithmic factors.

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