,
Venkatesan Guruswami
,
Aaron Putterman
Creative Commons Attribution 4.0 International license
The chain length of a set family 𝒮 ⊆ 2^[m] is the largest ascending sequence of sets in containment order in the union-closure of S. In this work, we provide a significantly simpler and more optimal characterization of the sparsifiability of set systems in terms of their chain length, improving on the work of Brakensiek and Guruswami [STOC 2025]. Our proof relies on a generalization of Karger’s [SODA 1993] famous contraction algorithm and its recent linear algebraic extensions [Khanna-Putterman-Sudan SODA 2024], and our resulting bounds show that, just as VC dimension characterizes the additive sparsifiability of a set system, chain length governs the multiplicative sparsifiability. As a corollary, we obtain improved bounds for weighted CSP sparsification.
@InProceedings{brakensiek_et_al:LIPIcs.ICALP.2026.44,
author = {Brakensiek, Joshua and Guruswami, Venkatesan and Putterman, Aaron},
title = {{Multiplicative Error Set System Sparsification: A Simpler Proof via Chain Length Contraction}},
booktitle = {53rd International Colloquium on Automata, Languages, and Programming (ICALP 2026)},
pages = {44:1--44:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-428-4},
ISSN = {1868-8969},
year = {2026},
volume = {374},
editor = {Bhattacharya, Sayan and Nanongkai, Danupon and Benedikt, Michael and Puppis, Gabriele},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2026.44},
URN = {urn:nbn:de:0030-drops-264331},
doi = {10.4230/LIPIcs.ICALP.2026.44},
annote = {Keywords: constraint satisfaction problem, chain length, sparsification, VC dimension}
}