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  • Titel: Improved Distance Queries and Cycle Counting by Frobenius Normal Form
  • Beteiligte: Sankowski, Piotr [Verfasser:in]; Wegrzycki, Karol [Verfasser:in]
  • Erschienen: Schloss Dagstuhl – Leibniz-Zentrum für Informatik, 2017
  • Sprache: Englisch
  • DOI: https://doi.org/10.4230/LIPIcs.STACS.2017.56
  • Schlagwörter: All Nodes Shortest Cycles ; Graph Algorithms ; Frobenius Normal Form
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  • Beschreibung: Consider an unweighted, directed graph G with the diameter D. In this paper, we introduce the framework for counting cycles and walks of given length in matrix multiplication time O-tilde(n^omega). The framework is based on the fast decomposition into Frobenius normal form and the Hankel matrix-vector multiplication. It allows us to solve the following problems efficiently. * All Nodes Shortest Cycles - for every node return the length of the shortest cycle containing it. We give an O-tilde(n^omega) algorithm that improves the previous O-tilde(n^((omega + 3)/2)) algorithm for unweighted digraphs. * We show how to compute all D sets of vertices lying on cycles of length c in {1, ., D} in randomized time O-tilde(n^omega). It improves upon an algorithm by Cygan where algorithm that computes a single set is presented. * We present a functional improvement of distance queries for directed, unweighted graphs. * All Pairs All Walks - we show almost optimal O-tilde(n^3) time algorithm for all walks counting problem. We improve upon the naive O(D n^omega) time algorithm.
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