Acknowledgments

I would like to thank everyone who has helped me advance this project (CHA), with special thanks to:

• Pablo-No whose GitHub issue got me interested in this problem, for fruitful conversations during the early stages of this project.
• Pooya Farshim, for very fruitful discussions about countless topics, including chess unwinnability. For all his help and comments on the research paper about this tool (which has been published at Fun with Algorithms 2022).
• Elena Gutiérrez, for all her support, help and comments on CHA's research paper.
• Antonio Nappa, for providing the hardware used for running CHA over the entire Lichess database.
• Andrew Buchanan, for very fruitful discussions about chess unwinnability and dead reckoning, for all his feedback and for sharing with me and letting me include two original compositions in the research paper. (I am also very thankful to Andrey Frolkin, co-author of one of them.)
• Maarten Loeffler for all his feedback about the research paper and for having found a gap in an earlier version of the proof of Lemma 8. Also for having identified, thanks to a deep understanding of our algorithm, a new class of positions that cannot be handled by our quick routine. For example: rnb1b3/pk1p4/p1pPp1p1/P1P1P1Pp/RBP4P/P7/5B2/7K . Consequently these artificial positions may fool the full routine when run with an insufficient search limit.
• All the anonymous reviewers of the 11th International Conference on Fun with Algorithms, for their valuable time, their careful reading of our manuscript and all their comments.
• The Stockfish Team, for their amazing and altruistic chess engine on which CHA relies.
• The Lichess Team, for the database of games used to test this tool and, of course, for making Lichess possible and for continuing improving it every day!
• George Wang, for all his support and interest in this project and for all his feedback.
• José María Gutiérrez, for his very careful reading of our research paper and all his support and feedback.
• Ricardo García, for all his support and interest in this project.
• Daniel Baechli, for many fruitful and deep conversations about this project and the FIDE rules. And for all his feedback and multiple suggestions.
• Daniel Dugovic, for his time on reviewing the preliminary version of this tool (D3).
• Niklas Fiekas, for mentioning this project in GitHub and for python-chess, which is amazing and I have used so many times in the past!
• Jesper Nørgaard, for having found and reported the first known position that CHA 2.2 could not classify correctly. CHA 2.4 now can!
• vonaka, for reviewing CHA's source code and proposing improvements on memory allocation.
• All the Lichess users who have commented on the Lichess Forum, in threads related to this tool.