arXiv:2601.19333cs.LGcs.DS2026-01

用弱比较预言机实现高效鲁棒的聚类,无需精确距离。

Metric $k$-clustering using only Weak Comparison Oracles

  • 仅通过四元组比较判断相对远近,替代传统距离计算。
  • 在任意度量空间下,查询复杂度为O(nk·polylog n),聚类代价为最优解常数倍。
  • 适用于大模型反馈等噪声低开销场景,适合大规模无监督学习应用。

聚类是无监督学习的基础任务,但经典算法(如k-均值、k-中位数)依赖精确的成对距离,在许多现代应用中不现实。本文研究在「排序模型(R-model)」下的聚类问题,其中完全用四元组预言机替代距离访问,该预言机仅提供相对距离比较。实际中,此类预言机可表示学习模型或人类反馈,通常具有噪声且存在访问成本。给定包含n个样本的度量空间,本文设计了随机化算法,仅使用噪声四元组预言机,输出O(k·polylog n)个中心,并将输入项映射到这些中心,使得映射的聚类代价至多为最优k-聚类代价的常数倍。所提方法在任意度量空间下查询复杂度为O(nk·polylog n),当度量空间具有有界膨胀维数时可优化至O((n+k²)·polylog n)。此时还能将近似比从常数提升至1+ε(ε>0任意小),同时保持相同的渐近查询复杂度。该框架展示了如何系统性地将噪声低开销预言机(如大语言模型生成)融入可扩展聚类算法。

原文摘要 · Abstract (English)

Clustering is a fundamental primitive in unsupervised learning. However, classical algorithms for $k$-clustering (such as $k$-median and $k$-means) assume access to exact pairwise distances -- an unrealistic requirement in many modern applications. We study clustering in the \emph{Rank-model (R-model)}, where access to distances is entirely replaced by a \emph{quadruplet oracle} that provides only relative distance comparisons. In practice, such an oracle can represent learned models or human feedback, and is expected to be noisy and entail an access cost. Given a metric space with $n$ input items, we design randomized algorithms that, using only a noisy quadruplet oracle, compute a set of $O(k \cdot \mathsf{polylog}(n))$ centers along with a mapping from the input items to the centers such that the clustering cost of the mapping is at most constant times the optimum $k$-clustering cost. Our method achieves a query complexity of $O(n\cdot k \cdot \mathsf{polylog}(n))$ for arbitrary metric spaces and improves to $O((n+k^2) \cdot \mathsf{polylog}(n))$ when the underlying metric has bounded doubling dimension. When the metric has bounded doubling dimension we can further improve the approximation from constant to $1+\varepsilon$, for any arbitrarily small constant $\varepsilon\in(0,1)$, while preserving the same asymptotic query complexity. Our framework demonstrates how noisy, low-cost oracles, such as those derived from large language models, can be systematically integrated into scalable clustering algorithms.

聚类弱比较预言机大模型

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