Creative Commons Attribution 4.0 International license
The bounded-degree query model, introduced by Goldreich and Ron (Algorithmica, 2002), is a standard framework in graph property testing and sublinear-time algorithms. Many properties studied in this model, such as bipartiteness and 3-colorability of graphs, can be expressed as satisfiability of constraint satisfaction problems (CSPs). We prove that for the entire class of unbounded-width CSPs, testing satisfiability requires Ω(n) queries in the bounded-degree model. This result unifies and generalizes several previous lower bounds. In particular, it applies to all CSPs that are known to be NP-hard to solve, including k-colorability of 𝓁-uniform hypergraphs for any k,𝓁 ⩾ 2 with (k,𝓁) ≠ (2,2). Our proof combines the techniques from Bogdanov, Obata, and Trevisan (FOCS, 2002), who established the first Ω(n) query lower bound for CSP testing in the bounded-degree model, with known results from universal algebra.
@InProceedings{fei:LIPIcs.APPROX/RANDOM.2026.31,
author = {Fei, Yumou},
title = {{Unbounded-Width CSPs Are Untestable in a Sublinear Number of Queries}},
booktitle = {Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2026)},
pages = {31:1--31:9},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-449-9},
ISSN = {1868-8969},
year = {2026},
volume = {392},
editor = {Singh, Mohit and Gur, Tom},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX/RANDOM.2026.31},
URN = {urn:nbn:de:0030-drops-277489},
doi = {10.4230/LIPIcs.APPROX/RANDOM.2026.31},
annote = {Keywords: constraint satisfaction problems, property testing}
}