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a commercial chess engine by [[Ubaldo Andrea Farina]], supporting both the [[Chess Engine Communication Protocol]] and [[UCI]], the [[PolyGlot]] and [[CTG]] <ref>[http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?tid=2319 CTG specification] by [[Steinar H. Gunderson|Sesse]], [[Computer Chess Forums|Rybka Forum]], September 30, 2007</ref> [[Opening Book#Formats|opening book formats]], various [[Endgame Tablebases|endgame tablebase]] and [[Endgame Bitbases|bitbase]] formats, and able to play [[Chess960]]. The development started in 2002 and it has been under continuous development, underwent a major rewrite in 2009 using [[Bitboards|bitboards]], and has been commercially released in October 2011 <ref>[http://www.talkchess.com/forum/viewtopic.php?t=40529 Chiron 1.0 available for preorder] by [[Ubaldo Andrea Farina]], [[CCC]], September 26, 2011</ref> . Chiron applies [[Parallel Search|parallel search]] on [https://en.wikipedia.org/wiki/Multiprocessor multiprocessor] systems, and has implemented [[Blockage Detection|pawn blockage detection]] function <ref>[[Eli David|Omid David]], [[Ariel Felner]], [[Nathan S. Netanyahu]] ('''2004'''). ''Blockage Detection in Pawn Endgames''. [[ICGA Journal#27_3|ICGA Journal, Vol. 27, No. 3]]</ref> <ref>[[Eli David|Omid David]], [[Ariel Felner]], [[Nathan S. Netanyahu]] ('''2004'''). ''[http://link.springer.com/chapter/10.1007/11674399_13 Blockage Detection in Pawn Endings]''. [[CG 2004]]</ref>, improved to detect blockages not only in [[Pawn Endgame|pawn endgame]] but also when there are a few pieces on the board <ref>[https://web.archive.org/web/20120122012655/http://www.chironchess.com/index.php/component/content/article/69 .:: Chiron Chess Engine ::.: | Pawn Blockages]([https://en.wikipedia.org/wiki/Wayback_Machine Wayback Machine], January 22, 2012)</ref> <ref>[http://www.talkchess.com/forum/viewtopic.php?t=40748 Code of Chiron for Detection of Pawn Blockages] by [[Ubaldo Andrea Farina]], [[CCC]], October 13, 2011</ref> <ref>[http://www.talkchess.com/forum/viewtopic.php?t=41569 Chiron 1.1 bug?] by [[Richard Vida]], [[CCC]], December 24, 2011</ref>. Chiron is available as [[Windows]] and [[Android]] version.

Chiron '''2''', released in December 2013 is about 40 Elo points stronger than Chiron 1.5 thanks to improvements in both [[Search|search]] and [[Evaluation|evaluation]] <ref>[httphttps://www.chironchess.com/news/34-news/77-chiron-2-released .:: Chiron Chess Engine ::.: / Chiron 2 released]</ref>.

The next major release in May 2016, Chiron '''3''', is about 60 Elo stronger than 2, due to further search and evaluation enhancements and tuning, and also supports [[Syzygy Bases]] and is able to probe of 6-men [[Scorpio Bitbases]] <ref>[httphttps://www.chironchess.com/news/34-news/80-chiron-3-released .:: Chiron Chess Engine ::.: / Chiron 3 released]</ref>.

On January 10, 2017, Chiron '''4''' was released, again a considerable improvement of about 70 Elo over its predecessor, Chiron 4 improved in a further [[Automated Tuning|tuned]] [[Evaluation|evaluation]], specially considering [[Passed Pawn|passed pawns]] and [[Mobility|mobility]], and various [[Search|search]] enhacements, such as better [[Pruning|forward pruning]], [[Lazy SMP]] and [[NUMA]] awareness <ref>[httphttps://www.chironchess.com/chiron-4-released/ Chiron 4 released], January 10, 2017</ref>. ==Chiron 5==Chiron '''5''' was released on June 21, 2021. It is about 110/120 points stronger than Chiron 4. Most of the gains come from improvements in [[Search|search]] and [[Move Ordering|move ordering]] but also the [[Evaluation|evaluation]] has been improved and [[Automated Tuning|tuned]] by playing several million games <ref>[https://www.chironchess.com/chiron-5-released/ Chiron 5 released]</ref>.

by [[Ubaldo Andrea Farina]], 2011 <ref>[httphttps://www.chironchess.com/index.phpabout/about .:: Chiron Chess Engine ::.: | About]</ref> <ref>Thank you! ([[Gerd Isenberg]], April 22, 2012) My own contribution to [[Magic Bitboards]] was the line-wise forerunner, dubbed [[Kindergarten Bitboards]], also tried with "random" factors, while [[Lasse Hansen]] had the idea to hash both lines simultaneously. I was initially skeptical whether the huge tables pay off.</ref> In these nine years Chiron has improved a lot thanks also to ideas found in strong [[:Category:Open Source||open source engines]], in [[Computer Chess Forums|computer chess forums]] and websites, etc. In particular I would like to thank [[Fabien Letouzey]], [[Tord Romstad]], [[Robert Hyatt]], the [[Ippolit]] guys, [[Ed Schroder|Ed Schröder]], [[Bruce Moreland]], [[Ernst A. Heinz|Ernst Heinz]] and many others. Thanks to [[Miguel A. Ballicora|Miguel Ballicora]], [[Eugene Nalimov]] and [[Daniel Shawul]] for the probing code of their [[Endgame Tablebases|tablebases]]/[[Endgame Bitbases|bitbases]], to [[Pradu Kannan]], [[Gerd Isenberg]] and [[Lasse Hansen]] for the [[Magic Bitboards|magic bitboards]], to [[Steinar H. Gunderson|Sesse]] and [[Stephan Vermeire]] for the [[CTG|CTG specifications]], to [[Ilari Pihlajisto]] for [[Cutechess-cli|cutechess-cli]] that I've been using since 2009 for testing Chiron with very fast games. Thanks to all the people that tested Chiron in the past, among them [[Ciro Luigi Vignotto|Ciro Vignotto]], [[Leo Dijksman]], [[Olivier Deville]], [[Günther Simon]], [[Lars Hallerström]], the testers of [[CEGT]] and [[CCRL]] and many others. Thanks to [[Wilhelm Hudetz]] for the Chiron logo. Finally, thanks to [[Salvo Spitaleri]] who has been the [[:Category:Opening Book AuthorsAuthor|opening book author]] of Chiron since 2006.

* [httphttps://www.chironchess.com/ .:: Chiron Chess Engine ::.:]: [httphttps://www.chironchess.com/news/34-news/74-chiron-153-released / Chiron 1.5 3 released], November May 01, 20122016: [httphttps://www.chironchess.com/news/34-news/77-chiron-2-released Chiron 2 released], December 13, 2012: [http://www.chironchess.com/chiron-34-released/ Chiron 3 4 released], May 01January 10, 20162017 : [httphttps://www.chironchess.com/chiron-45-released/ Chiron 4 5 released], January 10June 21, 2017 2021