Unfortunately, given the restrictions imposed by the COVID-19 pandemic, the Organizing Committee and the Technical Programa Chairs of ALGO 2021 were forced to run the meetings fully online, using a specialised platform. Instructions for authors and attendees on how to participate in the virtual meeting will be provided shortly..


The International Symposium on Parameterized and Exact Computation (IPEC) is an annual conference covering all aspects of parameterized and exact algorithms and complexity. Its 16th edition will be part of ALGO 2021, which also hosts ESA 2021 and a number of more specialized conferences and workshops. ALGO 2021 will take place on September 6-10, 2021, Lisbon, Portugal. Due to the COVID-19 pandemic, IPEC might be partially or completely held online.

Important Dates

  • Paper Registration(extended): June 29 (23:59 AoE), 2021
  • Full Paper Submission(extended): June 29 (23:59 AoE), 2021
  • Notification of acceptance: July 30, 2021
  • Camera ready: October 10, 2021
  • Conference dates: September 8 - 10, 2021, in Lisbon, Portugal

Call For Papers

The 16th International Symposium on Parameterized and Exact Computation (IPEC 2021) invites papers presenting original research in the area of parameterized and exact algorithms and complexity.


The topics include but are not limited to:

  • new techniques for the design and analysis of parameterized and exact algorithms;
  • fixed-parameter tractability and kernelization results;
  • parameterized complexity theory;
  • parameterized (in)approximability results;
  • relationships between parameterized complexity and traditional complexity classifications;
  • applications of parameterized and exact computation;
  • implementation issues of exact, parameterized, and kernelization algorithms;
  • theoretically grounded studies on parameterized and exact computations and kernelization for real-world applications and algorithmic engineering.

Special Events

An invited talk is planned by the 2021 EATCS-IPEC Nerode Prize winner.
In addition, the results of the 5th Parameterized Algorithms and Computational Experiments Challenge (PACE 2021) will be presented in a special session.
The program will include an invited tutorial by Édouard Bonnet(CNRS, ENS Lyon, France), "Twin-width of graphs".


Accepted papers will be published in the symposium proceedings in the Leibniz International Proceedings in Informatics (LIPIcs) series, based at Schloss Dagstuhl. Authors of accepted papers are expected to present their work at the symposium, and to incorporate the comments from the program committee.

A special issue of Algorithmica is planned for selected papers presented at IPEC 2021.


The program committee may award a Best Paper Award and a Best Student Paper Award, both of which may be exceptionally split between two or more papers. A student is someone who has not received a PhD degree before the full paper submission deadline. A paper accepted to the conference is eligible for the Best Student Paper Award if either all its authors are students, or besides student co-author(s) there is one non-student co-author that confirms, at the moment of submission, that a clear majority of conceptual work on the paper was done by the student co-author(s). In the latter case, it is moreover expected that a student gives the presentation at the conference. Papers co- authored by members of the program committee are not eligible for the Best Paper Award or the Best Student Paper Award.

Submission Guidelines

Authors are invited to submit an extended abstract of up to 12 pages (excluding the title page and references section) in LIPIcs style, in English, describing original unpublished research. The title page consists exclusively of the title of the paper, author information, and abstract. Results previously published in another conference proceedings or journal (or scheduled for publication prior to IPEC) will not be considered. Simultaneous submission to other conferences with published proceedings or to journals is not allowed. However, the authors are encouraged to make full versions of their submissions freely accessible in an online repository such as arXiv or ECCC. Program committee members (except the co-chairs) are allowed to submit papers.

The extended abstract should contain a summary of the main results, their motivation and importance, and evidence of their correctness. All claims made in the extended abstract must be fully justified in a clearly marked appendix that will be read at the discretion of the program committee. The authors may choose to either present in the appendix only the material excluded from the extended abstract or to attach a full version of the paper as the appendix. In either case, the authors should take a particular notice that the extended abstract should present their work in a comprehensible and self-contained way and the quality of the presentation in the extended abstract will be taken into account by the program committee. Authors must submit their papers electronically via EasyChair. The use of the LIPIcs style file (https://www.dagstuhl.de/en/publications/lipics/instructions-for-authors) is mandatory; no changes to font size, page margins, etc., are permitted.

Submission website: https://easychair.org/conferences/?conf=ipec2021

Programme Committee

  • Akanksha Agrawal, IIT Madras, India
  • Fahad Panolan, IIT Hyderabad, India
  • Dimitrios Thilikos, LIRMM, Université de Montpellier, CNRS, France
  • Eduard Eiben, Royal Holloway, University of London, UK
  • Ignasi Sau, LIRMM, Université de Montpellier, CNRS, France
  • Jesper Nederlof, Utrecht University, Netherlands
  • Jiehua Chen, Vienna University of Technology, Austria
  • Karl Bringmann, Saarland University, Germany
  • Karthik C. S., New York University, USA
  • Martin Koutecky, Charles University, Czech Republic
  • Meirav Zehavi (co-chair), Ben-Gurion University of the Negev, Israel
  • Pascal Schweitzer, TU Kaiserslautern, Germany
  • Petr Golovach (co-chair), University of Bergen, Norway
  • Sebastian Siebertz, University of Bremen, Germany
  • Saket Saurabh, Indian Institute of Mathematical Sciences, India, and University of Bergen, Norway
  • Nimrod Talmon,Ben-Gurion University of the Negev, Israel
  • Vincent Cohen-Addad, Google Zurich, Switzerland
  • William Lochet, University of Bergen, Norway

Accepted papers


Invited talks: Bakhadyr Khoussainov and Frank Stephan - "Parity Games - Background and Algorithms”

Parity games are games where a marker is moved on a finite graph and each node is annotated with a natural number; the game runs forever and the largest number in an infinitely often visited node decides the winner, if it is even then  player Anke wins else player Boris wins. Marcin Jurdzinski showed that this game is in UP intersected coUP and also provided the first not fully exponential algorithm for it; however, the exact time complexity remained unresolved. In 2017, Calude, Jain, Khoussainov, Li and Stephan found a quasipolynomial time algorithm which Jurdzinski and Lazic as well as Schewe and his collaborators improved to be in polynomial space as well. The talk provides the way this algorithm was found and the implications it has for the fixed-parameter-tracktability of parity games and related problems like coloured Muller games. Though now quite a number of quasipolynomial time algorithms are known and there is quite extensive research in this topic, the question on whether parity games can even be solved in polynomial time is still unresolved.

Tutorial: Édouard Bonnet “Twin-width”


Bakhadyr Khoussainov

University of Electronic Science and Technology of China, Cengdu, China and University of Auckland, Auckland, New Zealand

Bakhadyr Khoussainov is a professor in the University of Electronic Science and Technology of China and a professor of Computer Science at University of Auckland. His research interests include mathematical logic, computability theory, computable model theory, and algorithms. With Anil Nerode, he is the co-founder of the theory of automatic structures. In 2020, Bakhadyr Khoussainov was awarded Humboldt Prize in recognition of his research achievements.

Frank Stephan

National University of Singapore, Singapore

Frank Stephan is a professor in the Departments of Mathematics and Computer Science of the National University of Singapore. His research interests are within the areas of mathematical logic and theoretical computer science. In particular, he is working in recursion theory, inductive inference, automata theory, automatic structures, algorithmic randomness and computational complexity. Frank Stephan is an editor of the journal Computability and an associate editor of the Journal of Computer and System Sciences and a member of the editorial board of Information and Computation.

Édouard Bonnet

CNRS, ENS Lyon, France

Édouard Bonnet is a CNRS researcher at ENS Lyon. His research interests are in algorithms and complexity for graphs and geometric problems.


IPEC 2021 proceedings will to be published in the Leibniz International Proceedings in Informatics (LIPIcs) series after the conference.