,
Manoj Gupta
Creative Commons Attribution 4.0 International license
We are given an undirected weighted graph G with n vertices and m edges, edge weights in [1, W], and a designated source vertex s. We design a single source dual fault tolerant distance oracle for G. Given a destination vertex t and a set F of at most two faulty edges, the oracle returns a (1 + O(ε))-approximation of the weight of the shortest path from the source s to t avoiding F. Our oracle uses Õ(n√n) space and has Õ(1) query time. Prior to our result, single source single fault tolerant oracles were known to return a (1+ε) approximation of the weight of the shortest path using Õ(n) space and O(1) query time. However, extending these approaches to multiple faults remained an open problem. Indeed, all (1+ε)-approximate distance oracles that handle multiple faults require Ω(n²) space. We break this bound by presenting the first dual fault tolerant distance oracle with o(n²) space.
@InProceedings{das_et_al:LIPIcs.ESA.2026.90,
author = {Das, Koustav and Gupta, Manoj},
title = {{Approximate Single Source Dual Fault Tolerant Distance Oracle}},
booktitle = {34th Annual European Symposium on Algorithms (ESA 2026)},
pages = {90:1--90:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-445-1},
ISSN = {1868-8969},
year = {2026},
volume = {388},
editor = {Bille, Philip and Pettie, Seth and Storandt, Sabine},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2026.90},
URN = {urn:nbn:de:0030-drops-272263},
doi = {10.4230/LIPIcs.ESA.2026.90},
annote = {Keywords: Fault-tolerant distance oracle, Shortest paths, Graph algorithms, Dual failures, Approximate distance oracle}
}