,
Ulrich Meyer
,
Manuel Penschuck
Creative Commons Attribution 4.0 International license
A graph is called a (k, ρ)-graph iff every node can reach ρ of its nearest neighbors in at most k hops. This property has proven useful in the analysis and design of parallel shortest-path algorithms [Blelloch et al., 2016; Dong et al., 2021]. Any graph can be transformed into a (k, ρ)-graph by adding shortcuts. Formally, the (k,ρ)-Minimum-Shortcut-Problem (kρ-MSP) asks to find an appropriate shortcut set of minimal cardinality. We show that kρ-MSP is NP-complete in the practical regime of k ≥ 3 and ρ = Θ(n^ε) for ε > 0. With a related construction, we bound the approximation factor of known kρ-MSP heuristics [Blelloch et al., 2016] from below and propose algorithmic countermeasures improving the approximation quality. Further, we describe an integer linear problem (ILP) that optimally solves kρ-MSP. Finally, we compare the practical performance and quality of all algorithms empirically.
@InProceedings{leonhardt_et_al:LIPIcs.ESA.2024.84,
author = {Leonhardt, Alexander and Meyer, Ulrich and Penschuck, Manuel},
title = {{Insights into (k, \rho)-Shortcutting Algorithms}},
booktitle = {32nd Annual European Symposium on Algorithms (ESA 2024)},
pages = {84:1--84:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-338-6},
ISSN = {1868-8969},
year = {2024},
volume = {308},
editor = {Chan, Timothy and Fischer, Johannes and Iacono, John and Herman, Grzegorz},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2024.84},
URN = {urn:nbn:de:0030-drops-211554},
doi = {10.4230/LIPIcs.ESA.2024.84},
annote = {Keywords: Complexity, Approximation, Optimal algorithms, Parallel shortest path}
}
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