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Efficient shortest paths in scale-free networks with underlying hyperbolic geometry. (English) Zbl 07375947
Chatzigiannakis, Ioannis (ed.) et al., 45th international colloquium on automata, languages, and programming. ICALP 2018, Prague, Czech Republic, July 9–13, 2018. Proceedings. Wadern: Schloss Dagstuhl – Leibniz Zentrum für Informatik. LIPIcs – Leibniz Int. Proc. Inform. 107, Article 20, 14 p. (2018).
Summary: A common way to accelerate shortest path algorithms on graphs is the use of a bidirectional search, which simultaneously explores the graph from the start and the destination. It has been observed recently that this strategy performs particularly well on scale-free real-world networks. Such networks typically have a heterogeneous degree distribution (e.g., a power-law distribution) and high clustering (i.e., vertices with a common neighbor are likely to be connected themselves). These two properties can be obtained by assuming an underlying hyperbolic geometry.
To explain the observed behavior of the bidirectional search, we analyze its running time on hyperbolic random graphs and prove that it is $$\widetilde{\mathcal{O}}(n^{2- 1/\alpha}+ n^{1/(2\alpha)}+\delta_{\max})$$ with high probability, where $$\alpha\in(0.5,1)$$ controls the power-law exponent of the degree distribution, and $$\delta_{\max}$$ is the maximum degree. This bound is sublinear, improving the obvious worst-case linear bound. Although our analysis depends on the underlying geometry, the algorithm itself is oblivious to it.
For the entire collection see [Zbl 1392.68012].
##### MSC:
 68Nxx Theory of software 68Qxx Theory of computing