arXiv:2510.15076cs.LGcs.DM2025-10被引 1

首个在线相关聚类算法,能同时优化所有ℓ_p范数。

Online Correlation Clustering: Simultaneously Optimizing All $\ell_p$-norms

  • 基于小样本预览设计统一算法,实现多范数同步优化
  • 对ℓ₁-范数期望常数竞争力,ℓ_∞-范数高概率对数竞争力
  • 解决在线场景下公平性与全局误差的权衡难题

相关聚类的ℓ_p-范数目标在最小化总错误(ℓ₁-范数)与保障单个节点公平性(ℓ_∞-范数)之间存在根本权衡。令人惊讶的是,在离线设置下可仅用一个聚类同时近似所有ℓ_p-范数。这一强大保证能否在在线场景中实现?本文首次给出肯定答案。我们提出一种针对在线带样本(AOS)模型的单一算法:给定输入的恒定小比例作为样本,该算法能在高概率下实现所有ℓ_p-范数的O(log⁴n)竞争比,对ℓ_∞-范数达到高概率O(logn)竞争比,对ℓ₁-范数在期望下为O(1)竞争比。本工作成功将离线‘全范数’保证推广至在线世界。研究动机来自一项新硬性结果:在标准随机顺序(RO)在线模型中,ℓ₁-范数虽可常数近似,但任何针对促进公平性的ℓ_∞-范数算法的竞争力至少为Ω(n^{1/3}),凸显了超越最坏情况模型的必要性。我们进一步通过下界证明,所提算法在AOS模型中对ℓ₁和ℓ_∞-范数的竞争比几乎紧致。

原文摘要 · Abstract (English)

The $\ell_p$-norm objectives for correlation clustering present a fundamental trade-off between minimizing total disagreements (the $\ell_1$-norm) and ensuring fairness to individual nodes (the $\ell_\infty$-norm). Surprisingly, in the offline setting it is possible to simultaneously approximate all $\ell_p$-norms with a single clustering. Can this powerful guarantee be achieved in an online setting? This paper provides the first affirmative answer. We present a single algorithm for the online-with-a-sample (AOS) model that, given a small constant fraction of the input as a sample, produces one clustering that is simultaneously $O(\log^4 n)$-competitive for all $\ell_p$-norms with high probability, $O(\log n)$-competitive for the $\ell_\infty$-norm with high probability, and $O(1)$-competitive for the $\ell_1$-norm in expectation. This work successfully translates the offline "all-norms" guarantee to the online world. Our setting is motivated by a new hardness result that demonstrates a fundamental separation between these objectives in the standard random-order (RO) online model. Namely, while the $\ell_1$-norm is trivially $O(1)$-approximable in the RO model, we prove that any algorithm in the RO model for the fairness-promoting $\ell_\infty$-norm must have a competitive ratio of at least $Ω(n^{1/3})$. This highlights the necessity of a different beyond-worst-case model. We complement our algorithm with lower bounds, showing our competitive ratios for the $\ell_1$- and $\ell_\infty$- norms are nearly tight in the AOS model.

在线学习聚类算法多范数优化

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