Rybka
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| Developer(s) | Vasik Rajlich |
|---|---|
| Stable release |
4.1 / March 5, 2011
|
| Operating system | Windows |
| Type | Chess engine |
| License | Proprietary |
| Website | rybkachess |
Rybka is a computer chess engine designed by International Master Vasik Rajlich. Around 2011 Rybka was one of the top-rated engines on chess engine rating lists and has won many computer chess tournaments.
After Rybka won four consecutive World Computer Chess Championships from 2007 to 2010, it was stripped of these titles after the International Computer Games Association concluded in June 2011 that Rybka was plagiarized from both the Crafty and the Fruit chess engines and so failed to meet their originality requirements. The ICGA proceedings against Rybka were subsequently upheld by the FIDE Ethics Commission, saying "the ICGA has not violated the FIDE Code of Ethics, nor any other FIDE rule or general principle of law". However, the same FIDE Ethics Commission ruled that banning Rajlich for life failed to have a clear statutory basis and sufficient procedural guarantees, and so they sanctioned ICGA with a warning.
Rajlich has now agreed to underpin the Fritz brand of ChessBase, merging Rybka to produce Fritz 15 released in late 2015.
The word rybka, pronounced [ˈrɪpka], means little fish in Czech, Polish, and in many other Slavic languages. Vasik Rajlich was once asked in an interview by Alexander Schmidt, "Did you choose the name Rybka because your program always slipped out of your hands like a little fish?" He replied, "As for the name Rybka – I am sorry but this will remain my private secret."
Rybka is a closed-source program, but still some details have been revealed: Rybka uses a bitboard representation, and is an alpha-beta searcher with a relatively large aspiration window. It uses very aggressive pruning, leading to imbalanced search trees. The details of the evaluation function are unknown, but since version 2.3.1 it has included work by GM Larry Kaufman on material imbalances, much of which was worked out in a series of papers in the 1990s.
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