LIPIcs.FUN.2022.2.pdf
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A Practical Algorithm for Chess Unwinnability
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Miguel Ambrona 
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Volume:
11th International Conference on Fun with Algorithms (FUN 2022)
Series: Leibniz International Proceedings in Informatics (LIPIcs)
Conference: International Conference on Fun with Algorithms (FUN) - License:
Creative Commons Attribution 4.0 International license
- Publication Date: 2022-05-23
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Acknowledgements
Special thanks to Pooya Farshim, for very fruitful discussions and all his feedback; Elena Gutiérrez, for all her help and comments; Antonio Nappa, for providing the hardware; the Lichess Team; the Stockfish Team; and many others: https://chasolver.org/acks.html. I would also like to express my sincere gratitude to Andrew Buchanan and Andrey Frolkin, for sharing with me and letting me include two original compositions, and for all the feedback. Finally, I would like to thank Maarten Loeffler, for having found a gap in an earlier version of the proof of Lemma 8, and for all his comments. I am also very thankful to the other anonymous reviewers of FUN 2022, for their valuable time and careful reading of this manuscript.
Cite AsGet BibTex
Miguel Ambrona. A Practical Algorithm for Chess Unwinnability. In 11th International Conference on Fun with Algorithms (FUN 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 226, pp. 2:1-2:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)
https://doi.org/10.4230/LIPIcs.FUN.2022.2
https://doi.org/10.4230/LIPIcs.FUN.2022.2
Abstract
The FIDE Laws of Chess establish that if a player runs out of time during a game, they lose unless there exists no sequence of legal moves that ends in a checkmate by their opponent, in which case the game is drawn. The problem of determining whether or not a given chess position is unwinnable for a certain player has been considered intractable by the community and, consequently, chess servers do not apply the above rule rigorously, thus unfairly classifying many games.
We propose, to the best of our knowledge, the first algorithm for chess unwinnability that is sound, complete and efficient for practical use. We also develop a prototype implementation and evaluate it over the entire Lichess Database (containing more than 3 billion games), successfully identifying all unfairly classified games in the database.
Subject Classification
ACM Subject Classification
- Theory of computation → Design and analysis of algorithms
- Software and its engineering → Software libraries and repositories
Keywords
- chess
- helpmate
- unwinnability
- timeout
- dead position
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References
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