Rybka

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Rybka
Developed by Vasik Rajlich
Latest release 2.3.2a / June 18, 2007
OS Windows
Genre Chess engine
License Proprietary
Website rybkachess.com

Rybka is a computer chess engine created by International Master Vasik Rajlich. As of May 2008, Rybka is top-rated in all notable chess engine rating lists[1][2][3][4][5] and has won many official Computer Chess Tournaments including the 2007 World Computer-Chess Championship. Rybka supports both single processor and symmetric multiprocessing (SMP) systems.

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[edit] Name

The word rybka means little fish in the Czech language, where it is pronounced [ˈrɪpka]. 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 ."

It has been speculated that the name might be a pun on Bobby Fischer's last name; it might be also a diminutive used by him when speaking to his wife.

[edit] Playing strength

Rybka 1.0 beta (which is available as a free download) has been rated at 2809 Elo [6] (about the same strength as Toga II), and Rybka 2.3.1 is estimated to be about 200 Elo stronger than 1.0 beta.[citation needed] Newer versions of Rybka can also use multiple processors, yielding an estimated increase of 50 Elo per doubling of processors. [7]

Rybka's evaluation is considered one of its main advantages over rival programs.[8][9]

Rybka is significantly stronger – about 60% faster – when used in 64-bit mode than in 32-bit mode.[7]

[edit] Internals

Rybka is a closed-source program, but still some details have been revealed: Rybka uses a bitboard representation[10], and is an alpha-beta searcher with a relatively large aspiration window[11]. It uses very aggressive pruning, leading to imbalanced search trees[12]. The details of the evaluation function are unknown, but since version 2.3.1 it has included work by Larry Kaufman on material imbalances, much of which was worked out in a series of papers in the 90s.[13]

Rybka has been accused of being based on Fruit, but Rajlich has denied this categorically.[14] Comments by the programmer reveal Rybka does use some standard chess programming techniques, such as the null-move heuristic and aspiration windows, along with other null-window tricks.

[edit] Team

Iweta and Vasik Rajlich
Iweta and Vasik Rajlich

Vasik Rajlich is the main author of Rybka, with IM Larry Kaufman in primary charge of the evaluation function since version 2.3. Iweta Rajlich is the main Rybka tester. Jeroen Noomen (who used to work on Rebel) and Dagh Nielsen are the authors of its opening book.

[edit] History

 Please help improve this section by expanding it.
Further information might be found on the talk page or at requests for expansion.

The first Rybka beta was released on December 2, 2005.

[edit] Tournament participations

In 2005, from December 27 to December 30, Rybka participated in the 15th International Computer Chess Championship in Paderborn, Germany. Rybka won the tournament with a score of 5½ points out of 7, ahead of other engines such as Gandalf, Zappa, Spike, Shredder and Fruit.

On the CCT8 from February 25 to February 26, Rybka won with a score of 8 out of 9, going undefeated.

In the April 2006 PAL/CSS Freestyle main tournament, an unaided Rybka 1.1 took first place. In the final tournament, Rybka 1.1 finished in second and third place, behind Hydra.

In the 6th Leiden ICT in May 2006, Rybka won with a score of 8½ out of 9, ahead of Sjeng, Gandalf and Shredder.

At the 14th World Computer-Chess Championship in Turin, Italy in May 2006, Rybka, playing under the name Rajlich, finished second, tied with Shredder, after Junior, the winning 2006 World champion.

In the June 2006 PAL/CSS Freestyle main tournament, the Rybka team, playing under the handle Rajlich, tied for first place with Intagrand. In the final, the Rybka team took clear first place, a point ahead of the field. All 8 qualificants to the final were Rybka users.

In the 2006 Dutch Open Computer Championships, Rybka 2.2 finished in first place with a perfect score of 9 out of 9. [15]

In December 2006, Rybka participated in the 16th International Computer Chess Championship in Paderborn, Germany. Rybka won the tournament with a score of 6½ points out of 7. [1]

In February 2007 , Rybka participated in the CCT9 and Rybka won with 6/7. Rybka by Vasik Rajlich is CCT9 Champion

In the 7th Leiden ICT in May 2007, Rybka won with a score of 7½ out of 9, ahead of Zappa and HIARCS. [16]

Rybka won the 15th World Computer Chess Championship in June 2007 with a score of 10 out of 11.

The Rybka team, playing under the handle Rajlich, won the June 2007 PAL/CSS Freestyle final with a score of 6/9.

[edit] Rybka versus grandmaster challenges

Whilst Rybka has won a match with GM Jaan Ehlvest which involved giving a pawn odd to the human, IM Larry Kaufman of the Rybka team has pledged his own money to a human GM that can beat Rybka in a six-game match without material odds. GM Jaan Ehlvest was again chosen to play Rybka, getting twice the thinking time and white every match, with Rybka having only a three-move opening book, limited (512MB) hash size, and no endgame tablebases (the match being dubbed "Everything but a pawn"). The match ended 4.5-1.5 after three Rybka wins and three draws.[citation needed]

Rybka vs GM Dzindzichashvili - A Pawn and Move, was played as an eight-game match, March the 3rd-7th 2008. The result was 4-4.

[edit] Zappa match

In September 2007, Zappa defeated Rybka in a match, 5.5-4.5. The 180 move game was closing to a draw when both engines were approaching the 50-move rule, however, due to a feature of the Rybka engine, it moved a pawn to avoid a draw, thus resetting the counter for the 50-move rule. This led to a positional disadvantage that eventually allowed Zappa to whittle away Rybka's defenses, and win the game.[citation needed]

[edit] Future release plans

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The release date for Rybka 3.0 UCI is flexible, but the general target is spring 2008. The following features have been confirmed, though not all specifically for Rybka 3.0:

  • In an interview with Frank Quisinsky, Vasik Rajlich revealed plans for a future GUI that would "properly display chess knowledge to the user."[8], most likely in the form of graphical evaluation of the pieces on the board. The GUI is being developed by Convekta, and is currently in beta testing for a limited set of users.
  • Native Linux support has been confirmed without a specific date. Rajlich' view on this is: "Generally, I'd like to say that we'll support Linux from Rybka 3. However, schedules have a way of slipping, so no promises yet."[17] 32-bit Rybka does, however, run under WINE, and 64-bit Rybka runs under both Linux and Mac OS X using an experimental, Rybka-specific translation layer called microwine.[18]
  • Chess960 support was implemented for the Chess Classic Mainz 2007, where Rybka subsequently won the computer Chess960 tournament.[19][20]
  • Support for Pocket PCs and similar mobile devices.[21]
  • And naturally, general playing strength improvements, including increased multiprocessor improvements, increased search efficiency, and better position evaluation.[22]

Rajlich has asserted that Rybka will continue to use open protocols, both for normal operations as well as for the data presented by the Rybka 3 GUI.

[edit] Strelka Controversy

In May 2007, a new chess engine called Strelka appeared on the scene, claimed to be written by Yuri Osipov. Soon, there were allegations that Strelka was a clone of Rybka 1.0 beta, in the sense that it was a reverse-engineered and slightly modified version of Rybka.[23] Several players found Strelka to yield identical analysis to Rybka in a variety of different situations, even having the same bugs and weaknesses in some cases. Osipov, however, stated repeatedly on discussion boards that Strelka was based on Fruit, not Rybka, and that any similarities was either because Rybka also was based on Fruit, or because he had tuned the evaluation function to be as close as Rybka as possible.[24][25]

With the release of Strelka 2.0 beta, source code was included. Rajlich stated that the source made it "obvious" that Strelka 2.0 beta was indeed a Rybka 1.0 beta clone, although not without some improvements in certain areas. On basis of this, he claimed the source as his own and intended to re-release it under his own name[26], although this has not happened yet. He also made allegations that "Yuri Osipov" was a pen name. Osipov again denied the allegations of cloning, but as of 2008, there is generally consensus that Strelka is indeed a Rybka clone.[citation needed]

[edit] References

  1. ^ CCRL 40/40 - Pure list (2008-05-23). Retrieved on 2008-05-26.
  2. ^ CEGT 40/20. Chess Engines Grand Tournament (2008-05-25). Retrieved on 2008-05-26.
  3. ^ Computerschach und Spiele - Eternal Rating. Computerschach und Spiele (2007-03-18). Retrieved on 2008-05-21.
  4. ^ The SSDF Rating List. Swedish Chess Computer Association (2007-11-03). Retrieved on 2008-04-22.
  5. ^ Bayesian Elo Ratinglist WBEC Ridderkerk after edition 14. Retrieved on 2008-05-20.
  6. ^ Rybka
  7. ^ a b FAQ for Rybka 2.0-2.2n2
  8. ^ a b Interview with Vasik Rajlich
  9. ^ Rybka’s immortal game
  10. ^ rybka source code
  11. ^ Rybka search
  12. ^ Rybka search
  13. ^ Rybka @ Amsterdam 15th WCCC
  14. ^ Is Rybka a derivative of Fruit?
  15. ^ Rybkachess.com
  16. ^ International CSVN Tournament 2007
  17. ^ (Experimental) 64-bit Rybka on Linux
  18. ^ (Experimental) 64-bit Rybka on Linux
  19. ^ Rybka in Chess Classic Mainz 2007, Chess 960
  20. ^ CCM7 - 3. Livingston Chess960 Computer-Weltmeisterschaft. Chess Tigers. Retrieved on 2007-08-22.
  21. ^ I want know if rybka will be developed for pocketpc
  22. ^ No new Rybka version for the next six month?
  23. ^ Strelka 1.0 x32:Rybka clone?
  24. ^ Strelka = Rybka 1.0
  25. ^ osipovs arguments about strelka
  26. ^ Strelka 2.0

[edit] External links