,
Buddha Dev Das
,
Arijit Ghosh
,
Gopinath Mishra
Creative Commons Attribution 4.0 International license
We study the problem of estimating the number of edges in an undirected, unweighted graph using sublinear query access. We consider a query model that preserves the structure of Independent Set (IS) queries, but augments their output with a random certificate: given a vertex subset, the oracle returns a uniformly random edge from the induced subgraph if one exists, and returns null otherwise.
Using this access, we give a randomized algorithm that outputs a (1 ± ε)-approximation to the number of edges with constant success probability using Õ(log² m) queries. This implies an exponential separation from both standard IS queries and global random edge-sampling models: estimating the number of edges using standard IS queries require Θ̃(min {√m, n/√m}) queries, while direct random edge-sample access requires Θ̃(√m) samples. Beyond separation in query complexity, our algorithm is output-sensitive: its query complexity is polylogarithmic in the number of edges in the graph. This aligns with the classical objective in group testing, where one seeks algorithms that are both worst-case optimal and instance-adaptive.
Conceptually, our model connects group testing, the decision-versus-counting dichotomy, graph property testing, and the "power of a random certificate", and can be viewed as a structured form of conditional sampling of edges in graphs.
@InProceedings{chanda_et_al:LIPIcs.APPROX/RANDOM.2026.41,
author = {Chanda, Debarshi and Das, Buddha Dev and Ghosh, Arijit and Mishra, Gopinath},
title = {{From Decision to Random Certificates: Exponential Separation for Edge Estimation with Independent Set Queries}},
booktitle = {Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2026)},
pages = {41:1--41:23},
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.2026.41},
URN = {urn:nbn:de:0030-drops-277584},
doi = {10.4230/LIPIcs.APPROX/RANDOM.2026.41},
annote = {Keywords: Property Testing, Edge Estimation}
}