We show that the eccentricities, diameter, radius, and Wiener index of an undirected n-vertex graph with nonnegative edge lengths can be computed in time O(n * binom{k+ceil[log n]}{k} * 2^k k^2 log n), where k is the treewidth of the graph. For every epsilon>0, this bound is n^{1+epsilon}exp O(k), which matches a hardness result of Abboud, Vassilevska Williams, and Wang (SODA 2015) and closes an open problem in the multivariate analysis of polynomial-time computation. To this end, we show that the analysis of an algorithm of Cabello and Knauer (Comp. Geom., 2009) in the regime of non-constant treewidth can be improved by revisiting the analysis of orthogonal range searching, improving bounds of the form log^d n to binom{d+ceil[log n]}{d}, as originally observed by Monier (J. Alg. 1980). We also investigate the parameterization by vertex cover number.
@InProceedings{bringmann_et_al:LIPIcs.IPEC.2018.4, author = {Bringmann, Karl and Husfeldt, Thore and Magnusson, M\r{a}ns}, title = {{Multivariate Analysis of Orthogonal Range Searching and Graph Distances}}, booktitle = {13th International Symposium on Parameterized and Exact Computation (IPEC 2018)}, pages = {4:1--4:13}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-084-2}, ISSN = {1868-8969}, year = {2019}, volume = {115}, editor = {Paul, Christophe and Pilipczuk, Michal}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2018.4}, URN = {urn:nbn:de:0030-drops-102050}, doi = {10.4230/LIPIcs.IPEC.2018.4}, annote = {Keywords: Diameter, radius, Wiener index, orthogonal range searching, treewidth, vertex cover number} }
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