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a chess program by primary author [[Victor Vikhrev]] and [[Alexey Manjakhin]]. Its development already started in 1971, when Victor Vikhrev wrote his first chess program in [[Algol]] for the [https://en.wikipedia.org/wiki/BESM-6 BESM-6]. During the 80s the program was re-written in [[Pascal]] to run on an [[IBM PC]] <ref>http://adamant1.fromru.com/centaur.html Кентавр (Russian, as of October 2018 no longer available)</ref> <ref>[https://chesspro.ru/guestnew/looknullmessage/?themeid=54&id=31&page=10#54-31-4381 ChessPro online | Шахматный форум | Новости мира движков] (Russian)</ref>. As one of the rare instances of a [[Best-First|best-first]] searcher, Centaur keeps its complete [[Search Tree|search tree]] in [[Memory|memory]] considering multiple optimistic, realistic and pessimistic [[Evaluation|evaluation]] scores, and to grow the tree based on [https://en.wikipedia.org/wiki/Probability_distribution probability distribution] based on those scores, it seems quite similar to [[Hans BerlinerAndrew James Palay|Berliner's]] and [[Chris McConnell|McConnellPalay's]] [[B*#ProbabilityBasedSearch|PB*]] <ref>[[Andrew James Palay]] ('''1983'''). ''Searching with Probabilities''. Ph.D. thesis, [[Carnegie Mellon University]], [http://www.dtic.mil/dtic/tr/fulltext/u2/a221478.pdf pdf]</ref> <ref>[[Hans Berliner]], [[Chris McConnell]] ('''1995'''). ''B* Probability Based Search.'' [[Carnegie Mellon University]] Computer Science research report</ref>. A [[MS-DOS|DOS]] version of Centaur featuring a [[3D Graphics Board|3D graphics board]] was released in the early 90s, a 16-bit [[Windows|Windows 3.x]] version was commercially available since the mid 90s <ref>[http://www.foro.meca-web.es/viewtopic.php?f=9&t=72&start=50#p8510 Re: La Máquina Preservadora. Programas de Ajedrez] by Tibono, [[Computer Chess Forums|Meca Foro]], October 09, 2015 (Spanish)</ref>.