PACE Solver Description: Zygosity

Authors Emmanuel Arrighi , Pål Grønås Drange , Kenneth Langedal , Farhad Vadiee , Martin Vatshelle, Petra Wolf

Thumbnail PDF


  • Filesize: 471 kB
  • 3 pages

Document Identifiers

Author Details

Emmanuel Arrighi
  • University of Trier, Germany
Pål Grønås Drange
  • University of Bergen, Norway
Kenneth Langedal
  • University of Bergen, Norway
Farhad Vadiee
  • University of Bergen, Norway
Martin Vatshelle
  • University of Bergen, Norway
Petra Wolf
  • University of Bergen, Norway

Cite AsGet BibTex

Emmanuel Arrighi, Pål Grønås Drange, Kenneth Langedal, Farhad Vadiee, Martin Vatshelle, and Petra Wolf. PACE Solver Description: Zygosity. In 18th International Symposium on Parameterized and Exact Computation (IPEC 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 285, pp. 39:1-39:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


The graph parameter twin-width was recently introduced by Bonnet et al. Twin-width is a parameter that measures a graph’s similarity to a cograph, which is a graph that can be reduced to a single vertex by repeatedly contracting twins. This brief description introduces Zygosity, a heuristic for computing a low-width contraction sequence that achieved second place in the 2023 edition of Parameterized Algorithms and Computational Experiments Challenge (PACE). Zygosity starts by repeatedly contracting twins. Then, any attached trees are contracted down to a single pendant vertex. The remaining graph is then contracted using a randomized greedy algorithm.

Subject Classification

ACM Subject Classification
  • Mathematics of computing → Graph algorithms
  • Twin-width
  • randomized greedy algorithm


  • Access Statistics
  • Total Accesses (updated on a weekly basis)
    PDF Downloads


  1. Édouard Bonnet, Eun Jung Kim, Stéphan Thomassé, and Rémi Watrigant. Twin-width I: tractable FO model checking. ACM Journal of the ACM (JACM), 69(1):1-46, 2021. Google Scholar
Questions / Remarks / Feedback

Feedback for Dagstuhl Publishing

Thanks for your feedback!

Feedback submitted

Could not send message

Please try again later or send an E-mail