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Approximating Pathwidth for Graphs of Small Treewidth

Published: 09 March 2023 Publication History

Abstract

We describe a polynomial-time algorithm which, given a graph G with treewidth t, approximates the pathwidth of G to within a ratio of \(O(t\sqrt {\log t})\). This is the first algorithm to achieve an f(t)-approximation for some function f.
Our approach builds on the following key insight: every graph with large pathwidth has large treewidth or contains a subdivision of a large complete binary tree. Specifically, we show that every graph with pathwidth at least th+2 has treewidth at least t or contains a subdivision of a complete binary tree of height h+1. The bound th+2 is best possible up to a multiplicative constant. This result was motivated by, and implies (with c=2), the following conjecture of Kawarabayashi and Rossman (SODA’18): there exists a universal constant c such that every graph with pathwidth Ω(kc) has treewidth at least k or contains a subdivision of a complete binary tree of height k.
Our main technical algorithm takes a graph G and some (not necessarily optimal) tree decomposition of G of width t′ in the input, and it computes in polynomial time an integer h, a certificate that G has pathwidth at least h, and a path decomposition of G of width at most (t′+1)h+1. The certificate is closely related to (and implies) the existence of a subdivision of a complete binary tree of height h. The approximation algorithm for pathwidth is then obtained by combining this algorithm with the approximation algorithm of Feige, Hajiaghayi, and Lee (STOC’05) for treewidth.

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  • (2024)On the structural hardness of answer set programmingProceedings of the Thirty-Eighth AAAI Conference on Artificial Intelligence and Thirty-Sixth Conference on Innovative Applications of Artificial Intelligence and Fourteenth Symposium on Educational Advances in Artificial Intelligence10.1609/aaai.v38i9.28923(10535-10543)Online publication date: 20-Feb-2024
  • (2024)Approximation Algorithms for Treewidth, Pathwidth, and Treedepth—A Short SurveyGraph-Theoretic Concepts in Computer Science10.1007/978-3-031-75409-8_1(3-18)Online publication date: 19-Jun-2024
  • (2023)Tight Bound on Treedepth in Terms of Pathwidth and Longest PathCombinatorica10.1007/s00493-023-00077-w44:2(417-427)Online publication date: 19-Dec-2023

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  1. Approximating Pathwidth for Graphs of Small Treewidth

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      Published In

      cover image ACM Transactions on Algorithms
      ACM Transactions on Algorithms  Volume 19, Issue 2
      April 2023
      367 pages
      ISSN:1549-6325
      EISSN:1549-6333
      DOI:10.1145/3582899
      • Editor:
      • Edith Cohen
      Issue’s Table of Contents

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      Association for Computing Machinery

      New York, NY, United States

      Publication History

      Published: 09 March 2023
      Online AM: 13 December 2022
      Accepted: 30 November 2022
      Revised: 24 November 2022
      Received: 29 March 2021
      Published in TALG Volume 19, Issue 2

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      Author Tags

      1. Treewidth
      2. pathwidth

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      • ERC
      • European Unions Horizon 2020 research and innovation programme
      • Polish National Agency for Academic Exchange (NAWA)

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      View all
      • (2024)On the structural hardness of answer set programmingProceedings of the Thirty-Eighth AAAI Conference on Artificial Intelligence and Thirty-Sixth Conference on Innovative Applications of Artificial Intelligence and Fourteenth Symposium on Educational Advances in Artificial Intelligence10.1609/aaai.v38i9.28923(10535-10543)Online publication date: 20-Feb-2024
      • (2024)Approximation Algorithms for Treewidth, Pathwidth, and Treedepth—A Short SurveyGraph-Theoretic Concepts in Computer Science10.1007/978-3-031-75409-8_1(3-18)Online publication date: 19-Jun-2024
      • (2023)Tight Bound on Treedepth in Terms of Pathwidth and Longest PathCombinatorica10.1007/s00493-023-00077-w44:2(417-427)Online publication date: 19-Dec-2023

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