Rybka

Infobox Software
name=Rybka


caption=
developer=Vasik Rajlich
latest_release_version=3
latest_release_date=August 6, 2008cite web | url=http://rybkachess.com/index.php?auswahl=Release+notes | title=Rybka 3 Release Notes | date=August 6,2008 | accessdate=2008-08-07]
operating_system=Windows
genre=Chess engine
license=Proprietary
website= [http://rybkachess.com/ 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 [cite web | url=http://www.computerchess.org.uk/ccrl/4040/rating_list_pure.html | title=CCRL 40/40 - Pure list | date=2008-05-23 | accessdate=2008-05-26] [cite web | url=http://www.husvankempen.de/nunn/rating.htm | title=CEGT 40/20 | date=2008-05-25 | publisher=Chess Engines Grand Tournament | accessdate=2008-05-26] [cite web | url=http://www.computerschach.de/index.php?option=com_wrapper&Itemid=242 | title=Computerschach und Spiele - Eternal Rating | date=2007-03-18 | publisher= "Computerschach und Spiele" | accessdate=2008-05-21] [cite web | url=http://ssdf.bosjo.net/list.htm | title=The SSDF Rating List | publisher=Swedish Chess Computer Association | date=2007-11-03 | accessdate=2008-04-22] [cite web | url=http://wbec-ridderkerk.nl/html/BayesianElo_ed14.htm | title=Bayesian Elo Ratinglist WBEC Ridderkerk after edition 14 | accessdate=2008-05-20] and has won many official Computer Chess Tournaments including the 2007 and 2008 World Computer Chess Championships. Rybka supports both single processor and symmetric multiprocessing (SMP) systems.

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."

Playing strength

Rybka 1.0 beta ( [http://www.superchessengine.com/rybka.htm which is available as a free download] ) has been rated at 2809 Elo [ [http://www.superchessengine.com/rybka.htm Rybka ] ] (about the same strength as Toga II), and Rybka 2.3.1 is estimated to be about 200 Elo stronger than 1.0 beta.Fact|date=June 2008 Newer versions of Rybka can also use multiple processors, yielding an estimated increase of 50 Elo per doubling of processors. [http://rybkachess.com/index.php?auswahl=FAQ+for+v+2.x FAQ for Rybka 2.0-2.2n2] ]

On September 26, 2008, the latest SSDF rating list was released, with Deep Rybka 3 in first place in the rankings with a rating of 3238.

Rybka's evaluation is considered one of its main advantages over rival programs. [http://www.top-5000.nl/int/rybka.htm Interview with Vasik Rajlich] ] [ [http://www.chessvibes.com/tournaments/rybkas-immortal-game/ Rybka’s immortal game] ]

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

Internals

Rybka is a closed-source program, but still some details have been revealed: Rybka uses a bitboard representation [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=20132#pid20132 rybka source code ] ] , and is an alpha-beta searcher with a relatively large aspiration window [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=19588#pid19588 Rybka search ] ] . It uses very aggressive pruning, leading to imbalanced search trees [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=17961#pid17961 Rybka search ] ] . 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. [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=15090#pid15090 Rybka @ Amsterdam 15th WCCC ] ]

Rybka has been accused of being based on Fruit, but Rajlich has denied this categorically. [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=19118#pid19118 Is Rybka a derivative of Fruit? ] ] 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.

Team

The Rybka team is unusual among computer chess teams in that several of its main members are strong chess players: Vasik Rajlich, the main author of Rybka as an International Master (IM). The same is IM Larry Kaufman, who is (from version 2.3) in primary charge of the evaluation function. Iweta Rajlich, Vasik Rajlich's wife and the main Rybka tester is a Women's GM (WGM) and IM. Jeroen Noomen (who used to work on Rebel) and Dagh Nielsen are the authors of its opening book -- the latter is one of the world's top freestyle chess players.

History

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

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 chess championship, Rybka 2.2 finished in first place with a perfect score of 9 out of 9. [ [http://www.rybkachess.com/docs/docc06.htm Rybkachess.com] ] 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. [ [http://wwwcs.uni-paderborn.de/~IPCCC/ 17th International Computer Chess Championship - IPCCC 2007 in Paderborn ] ]

In February 2007 , Rybka participated in the CCT9 and Rybka won with 6/7. [ [http://www.cctchess.info/index.html 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. [ [http://www.csvn.nl/index.php?option=com_content&task=view&id=258&Itemid=28 International CSVN Tournament 2007] ] 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. Later that year it won again the Dutch open computer chess championship, scoring 8/9. [ [http://www.csvn.nl/index.php?option=com_content&task=view&id=282&Itemid=46 Computerschaak - ONK 2007 ] ]

In October, 2008, Rybka won the 16th World Computer Chess Championship, held in Beijing, China, scoring 8/9.

Rybka versus grandmaster challenges

Whilst Rybka has [http://www.rybkachess.com/docs/RYBKA_EHLVEST_2007/Rybka_versus_GM_Ehlvest.htm 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 [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?tid=794;pg=1 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. [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?tid=1614 Rybka vs Ehlvest II - information center] ]

Rybka later played an eight-game match against GM Roman Dzindzichashvili with pawn and move odds, from March 3 to March 8. The result was 4-4, after two Rybka wins, 4 draws and 2 losses. [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?tid=3363 Rybka vs Dzindzichashvili - information center] ]

Zappa match

In September 2007, Zappa defeated Rybka in a match, 5½-4½. The 180 move game [http://www.chessgames.com/perl/chessgame?gid=1473884] was closing to a draw but was approaching the fifty move rule coming into effect. 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. [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?tid=2235]

Version 3

While previous versions of Rybka were released exclusively by Convekta, Rybka 3 was released by both Chessbase and Convekta. [Chessvine Article, [http://chessvine.com/archives/38-A-Little-Fish-Rybka-in-Corporate-Waters.html "A 'Little Fish' (Rybka) in Corporate Waters"] ] Although still a UCI engine, Rybka 3 has extra features when run under the ChessBase and Convekta user interfaces. In an interview with Frank Quisinsky, Vasik Rajlich revealed plans for a future GUI that would "properly display chess knowledge to the user.", most likely in the form of graphical evaluation of the pieces on the board. The GUI, named "Aquarium", is being developed by ChessOK (formerly known as Convekta). [ [http://chessok.com/?p=508 Rybka Aquarium: Interview with the Developers] ]

Chess960 support was implemented for the Chess Classic Mainz 2007, where Rybka subsequently won the computer Chess960 tournament. [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=14910#pid14910 Rybka in Chess Classic Mainz 2007, Chess 960 ] ] [cite web | url=http://chesstigers.de/ccm7/computer_wm.php?lang=0&kat=6&subkat=1 | title=CCM7 - 3. Livingston Chess960 Computer-Weltmeisterschaft | publisher=Chess Tigers | accessdate=2007-08-22]

There were many general playing strength improvements, including multiprocessor performance improvements, increased search efficiency, and better position evaluation. Three engine styles are supported: optimum, human, and dynamic. The opening book was improved to such an extent, that it is now also sold as a separate product. Chess engine rating lists which have already published results for Rybka 3 show it topping the rating lists ahead of the previous version of Rybka, sometimes by as much as 100 ELO points. [ [http://www.husvankempen.de/nunn/40_40%20Rating%20List/40_40%20All%20Versions/rangliste.html CEGT] ]

Future release plans

The following features have been confirmed for future versions:

* Native Linux support has been confirmed without a specific date. Release plan for platforms other than Windows is expected to come after Rybka 3.0 is finished. [http://chessok.com/?p=512] 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". [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=18932#pid18932 (Experimental) 64-bit Rybka on Linux ] ]
* Support for Pocket PCs and similar mobile devices. [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=18095#pid18095 I want know if rybka will be developed for pocketpc ] ]

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.Fact|date=July 2008

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. [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?tid=939 Strelka 1.0 x32:Rybka clone? ] ] 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 to Rybka as possible. [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=18905 Strelka = Rybka 1.0 ] ] [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?tid=3015 osipovs arguments about strelka ] ]

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 [ [http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?pid=39198#pid39198 Strelka 2.0 ] ] , 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.Fact|date=June 2008

"Rybka's Immortal Game"

A sacrificial brilliancy has been called "Rybka's Immortal Game", an allusion to the 1851 Immortal Game between Adolf Anderssen and Lionel Kieseritzky: [http://www.chessvibes.com/tournaments/rybkas-immortal-game Rybka's Immortal Game]

References

External links

* [http://www.rybkachess.com/ Official Site]
* [http://www.rybkaforum.net/ Official Forum]
* [http://wwwcs.uni-paderborn.de/~IPCCC/ The 15th International Computer Chess Championship]
* [http://www.computerchess.org.uk/ccrl/4040/ The CCRL Rating List]
* [http://www.husvankempen.de/nunn/rating.htm The CEGT Rating List]
*chessgames player|id=100439
* [http://chessok.com/?p=512 Interview with the Developers of Rybka 3]