,
Claudius Proissl
,
Sabine Storandt
Creative Commons Attribution 4.0 International license
The radius of a graph is an important structural parameter which plays a key role in social network analysis and related applications. It measures the minimum shortest path distance that is required to reach all nodes in the graph from a single node. A node from which all other nodes are within a distance equal to the radius is called a center of the graph. In a graph with n nodes and m edges, the center and the radius can be determined in Õ(nm) by computing shortest path distances between all pairs of nodes. Fine-grained complexity results suggest that asymptotically faster algorithms are unlikely to exist. In this paper, we describe a novel randomized algorithm for exact radius computation in weighted digraphs with an expected running time in Õ(d³m) where d is the so-called combinatorial dimension. Our methodology is inspired by Clarkson’s algorithm for LP-type problems. The value of d denotes the size of a basis, which is a smallest subset of nodes which enforce the same radius as the whole node set. While we show that there exist graphs with d ∈ Θ(n), our empirical analysis reveals that even large real-world graphs have small combinatorial dimension. This allows us to compute the radius in near-linear time on such instances. The significantly improved scalability can be clearly observed in our experimental evaluation on a diverse set of benchmark graphs.
@InProceedings{funke_et_al:LIPIcs.SEA.2025.17,
author = {Funke, Stefan and Proissl, Claudius and Storandt, Sabine},
title = {{Computing the Exact Radius of Large Graphs}},
booktitle = {23rd International Symposium on Experimental Algorithms (SEA 2025)},
pages = {17:1--17:14},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-375-1},
ISSN = {1868-8969},
year = {2025},
volume = {338},
editor = {Mutzel, Petra and Prezza, Nicola},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SEA.2025.17},
URN = {urn:nbn:de:0030-drops-232555},
doi = {10.4230/LIPIcs.SEA.2025.17},
annote = {Keywords: Radius, Graph Center, LP-type, Combinatorial Dimension}
}