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Main Authors: Cookson, Benjamin, Shah, Nisarg, Yu, Ziqi
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2601.00447
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author Cookson, Benjamin
Shah, Nisarg
Yu, Ziqi
author_facet Cookson, Benjamin
Shah, Nisarg
Yu, Ziqi
contents Proportional fairness criteria inspired by democratic ideals of proportional representation have received growing attention in the clustering literature. Prior work has investigated them in two separate paradigms. Chen et al. [ICML 2019] study centroid clustering, in which each data point's loss is determined by its distance to a representative point (centroid) chosen in its cluster. Caragiannis et al. [NeurIPS 2024] study non-centroid clustering, in which each data point's loss is determined by its maximum distance to any other data point in its cluster. We generalize both paradigms to introduce semi-centroid clustering, in which each data point's loss is a combination of its centroid and non-centroid losses, and study two proportional fairness criteria -- the core and, its relaxation, fully justified representation (FJR). Our main result is a novel algorithm which achieves a constant approximation to the core, in polynomial time, even when the distance metrics used for centroid and non-centroid loss measurements are different. We also derive improved results for more restricted loss functions and the weaker FJR criterion, and establish lower bounds in each case.
format Preprint
id arxiv_https___arxiv_org_abs_2601_00447
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publishDate 2026
record_format arxiv
spellingShingle Unifying Proportional Fairness in Centroid and Non-Centroid Clustering
Cookson, Benjamin
Shah, Nisarg
Yu, Ziqi
Computer Science and Game Theory
Proportional fairness criteria inspired by democratic ideals of proportional representation have received growing attention in the clustering literature. Prior work has investigated them in two separate paradigms. Chen et al. [ICML 2019] study centroid clustering, in which each data point's loss is determined by its distance to a representative point (centroid) chosen in its cluster. Caragiannis et al. [NeurIPS 2024] study non-centroid clustering, in which each data point's loss is determined by its maximum distance to any other data point in its cluster. We generalize both paradigms to introduce semi-centroid clustering, in which each data point's loss is a combination of its centroid and non-centroid losses, and study two proportional fairness criteria -- the core and, its relaxation, fully justified representation (FJR). Our main result is a novel algorithm which achieves a constant approximation to the core, in polynomial time, even when the distance metrics used for centroid and non-centroid loss measurements are different. We also derive improved results for more restricted loss functions and the weaker FJR criterion, and establish lower bounds in each case.
title Unifying Proportional Fairness in Centroid and Non-Centroid Clustering
topic Computer Science and Game Theory
url https://arxiv.org/abs/2601.00447