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Rybka (Computer)
Number of games in database: 213
Years covered: 2005 to 2016
Overall record: +141 -31 =41 (75.8%)*
   * Overall winning percentage = (wins+draws/2) / total games.

Repertoire Explorer
Most played openings
B90 Sicilian, Najdorf (10 games)
C42 Petrov Defense (7 games)
000 Chess variants (5 games)
B28 Sicilian, O'Kelly Variation (5 games)
D43 Queen's Gambit Declined Semi-Slav (5 games)
D47 Queen's Gambit Declined Semi-Slav (4 games)
C92 Ruy Lopez, Closed (4 games)
B51 Sicilian, Canal-Sokolsky (Rossolimo) Attack (4 games)
C78 Ruy Lopez (4 games)
A01 Nimzovich-Larsen Attack (3 games)

   🏆 TCEC Season 9 (stage 1a)
   Fizbo vs Rybka (May-20-16) 0-1
   Rybka vs Gull (May-19-16) 1-0
   Rybka vs Texel (May-17-16) 1-0
   Ginkgo vs Rybka (May-17-16) 1/2-1/2
   Hannibal vs Rybka (May-14-16) 0-1

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(born 2004) Czech Republic

[what is this?]
Rybka (Czech for "little fish") is a computer chess engine designed by IM Vasik G Rajlich. It supports both single processor and SMP systems. Iweta Radziewicz Rajlich is the main tester & Hans van der Zijden is one of her operators. Jeroen Noomen & Jiri Dufek co-authored her opening book. At the WCCC 2006 (2006), Rybka, playing under the name Rajlich, tied for 2nd place with Shredder (Computer), and behind the champion, Junior (Computer). Rybka won the 15th World Computer Chess Championship in Amsterdam, 2007 and the 16th World Computer Chess Championship in Beijing, September 28th to October 5th 2008 with 8.0/9 (+7 -0 =2). During 2009-10, she also became the World Computer Speed Chess Champion.

In 2011, the International Computer Games Association (ICGA) ruled that Raljich had plagiarized two other programs, Crafty and Fruit, disqualified him for life from competing in the World Computer Chess Championship and all other ICGA events, and stripped Rybka of the championship titles it had won in 2006 through 2010.

 page 1 of 9; games 1-25 of 213  PGN Download
Game  ResultMoves YearEvent/LocaleOpening
1. Spike vs Rybka 1-069200515. IPCCCE39 Nimzo-Indian, Classical, Pirc Variation
2. Rybka vs Jonny 1-0212005Blitz:110'C69 Ruy Lopez, Exchange, Gligoric Variation
3. Zappa vs Rybka 0-1772005IPCCCE12 Queen's Indian
4. Rybka vs Shredder ½-½572005IPCCCB90 Sicilian, Najdorf
5. Rybka vs Argonaut 1-0372005IPCCCC68 Ruy Lopez, Exchange
6. Rybka vs Gandalf 1-0462005?B12 Caro-Kann Defense
7. Ikarus vs Rybka 0-1572005IPCCCB00 Uncommon King's Pawn Opening
8. Shredder vs Rybka 0-1412006WBEC13 Premier Division,C50 Giuoco Piano
9. Ktulu vs Rybka  0-1502006Sonnabend_Div.Hardware_30minD43 Queen's Gambit Declined Semi-Slav
10. Rybka vs Granda Zuniga 1-0472006Torre ENTEL PCSB19 Caro-Kann, Classical
11. Leitao vs Rybka ½-½432006Torre ENTEL PCSD37 Queen's Gambit Declined
12. Rybka vs M Flores 1-0252006Copa Entel ,E10 Queen's Pawn Game
13. J Hellsten vs Rybka 0-1642006Torre ENTEL PCSD36 Queen's Gambit Declined, Exchange, Positional line, 6.Qc2
14. Rybka vs E Arancibia  1-0472006Copa Entel ,B07 Pirc
15. O Zambrana vs Rybka  0-1342006Copa Entel ,B41 Sicilian, Kan
16. Rybka vs E Cordova  ½-½742006Copa Entel ,B25 Sicilian, Closed
17. R Felgaer vs Rybka  0-1382006Copa Entel ,B51 Sicilian, Canal-Sokolsky (Rossolimo) Attack
18. J Alvarez Nunez vs Rybka  0-1442006Copa Entel ,C85 Ruy Lopez, Exchange Variation Doubly Deferred (DERLD)
19. Rybka vs L Rojas  1-0522006Copa Entel ,D90 Grunfeld
20. Zor Champ vs Rybka 1-0872006CSS/Pal Freestyle Tourney Final (45+5)B92 Sicilian, Najdorf, Opocensky Variation
21. Argonaut vs Rybka 0-14220066th International CSVN TournamentB50 Sicilian
22. Ant vs Rybka 0-13420066th International CSVN TournamentA58 Benko Gambit
23. Rybka vs Deep Gandalf 1-05720066th International CSVN TournamentC42 Petrov Defense
24. IsiChess vs Rybka 0-13720066th International CSVN TournamentA57 Benko Gambit
25. Rybka vs Shredder ½-½6720066th International CSVN TournamentA14 English
 page 1 of 9; games 1-25 of 213  PGN Download
  REFINE SEARCH:   White wins (1-0) | Black wins (0-1) | Draws (1/2-1/2) | Rybka wins | Rybka loses  

Kibitzer's Corner
< Earlier Kibitzing  · PAGE 9 OF 79 ·  Later Kibitzing>
Apr-20-06  monad: <whatthefat: >
I reckon this Rybka is a bit of a memory hog. Especially compared to a more sophisticated programme like Junior9.

When I had them play each other, I noticed that I could do things, like open PaintShopPro and do a screenshot, no prob. But only whilst Junior was 'thinking'. As soon as it was Rybka's turn to play, I couldn't even open PSP, let alone have it do something.

All that in spite of the vast difference in kN/s, with Junior using around 2000 and Rybka a mere 30. It seems that Rybka is not optimized for RAM use, the way most commercially established programmes are.

I would like to see it reviewed for a bunch of parameters, such as a floating points performance and other arithmetic tests. Does any one know if a Win Count Index measurement has been done on it?

Apr-20-06  monopole2313: I'm interested in writing my own computer chess program. I know C and assembly language but am fairly inexperienced as a programmer. Could someone suggest some introductory books or articles on writing chess programs? Thanks in advance!
Apr-20-06  Shajmaty: <monad: All that in spite of the vast difference in kN/s, with Junior using around 2000 and Rybka a mere 30. It seems that Rybka is not optimized for RAM use, the way most commercially established programmes are.> The analysis has been refined by Rybka: it "sees" in 1000 kN what other engines need 8000 kN. It usually beats Junior, by the way.
Premium Chessgames Member
  ganstaman: <monopole2313> I don't know of any materials out there that can help, but here's the little I know (or at least pretend to know). I would suggest first programming a chess game that is playable between two humans, where the computer at least recognizes illegal moves (make sure to get castling, en passant, recognizing check and checkmate, etc). This is all I've done before, and it's quite a task in itself.

Then you'd probably want to start on the AI portion of the program. So you'd have to determine what legal moves you have and then figure out an algorithm for evaluating positions. I would suggest making this algorithm well documented and easy to tweak since you likely will want to change often until you find the strongest combination of all your parameters.

One thing I've read somewhere (don't remember where, sorry), is that chess programs use a min-max thingy. That is, if it analyzed 4 ply (it moves, opponent moves, it moves, opponent moves), it assumes the opponent will chose the move at that 4th ply that minimizes the positional evaluation (worst move for computer, best for opponent). Then, the computer selects the 3rd ply move that maximizes the positional evaluation after the opponent selects his right 4th ply move. And the opponent would chose the move that minimizes that evaluation of the computer's maximized 3rd ply eval. In the end, the computer chooses the move that maximizes the evaluation after the opponent chooses the minimal move from what the computer maximized of what the opponent minimized.... etc. I feel that I'm getting confusing, so maybe I'd better let someone else (or some article or book) explain this better.

Good luck. Hope I helped at least a little.

Apr-21-06  RandomVisitor: <monopole2313>I would suggets that you get a copy of the free chess engine Crafty and take a look at it. The code is more complicated than you probably imagine.

Bob Hyatt has excellent notes where he explains what he is doing.

Premium Chessgames Member
  Appaz: <<monopole2313> writing my own computer chess program> Do a google search on the NegaMax algorithm.
Premium Chessgames Member
  Appaz: <RandomVisitor: <monopole2313> Crafty [...] The code is more complicated than you probably imagine.> Making a brute force chess playing program is quite easy. You need three bits of code: the NegaMax algorithm (to be called recursively for each ply), a simple evaluation function (to be called from NegaMax), and a logical chess board (to store the position of each recursion).
Premium Chessgames Member
  notyetagm: Rybka eval please for the following position with Black to play:

click for larger view

It is from the Fritz 5 tactical demolition Fritz vs Hertneck, 1998 after 17 ♖c1.

Apr-23-06  RandomVisitor: Rybka sees: 17...Qe4 18.Ng3 Qe6 19.Qf3 Bd6 +0.78/19. In this game, after 17...Qe6 18.Qf3 Black errs with 18...Rg8 allowing white rook penetration to the 7th rank. Better was the simple 18...a5.
Apr-23-06  RandomVisitor: <Appaz>Thank you for that info.
Apr-23-06  monad: <Rybka sees: 17...Qe4 18.Ng3 Qe6 19.Qf3 Bd6 +0.78/19. >

So does Junior 9 at 19 ply, but its evaluation is higher: +1.44. Continuation 20.b3 Rg8 21.Qxb7 Rad8 22.Rce1

Premium Chessgames Member
  notyetagm: Thanks for the evals, <RV> and <monad>.
Premium Chessgames Member
  notyetagm: Rybka eval please of the following critical position from Leko vs Kramnik, 2004:

click for larger view

Black has just played 30 ... ♖f8-g8, with terrible pressure against g2.

In the actual game White (Leko) played 31 ♕h3? and cracked under this enormous kingside pressure, going down in flames in just six more moves.

What should White have played in this position? On the kibitzing page for this game you will find ideas of ♔h1/♖g1 and also ♔f1.


Apr-24-06  AlexandraThess: <notyetagm> Kf1 is aimless move - after Qh4 white have to resign.This move give Black a tempo to remove the Queen from the 5th rank and this makes possible moves like Rh5,Rg5. For example - 31.Kf1 Qh4 32. Kg1 (on 32.g3 simply follows Q:h2)32... Qf2+ - and white loses his bishop. In my view the best move is 31.Kh1 , since black cannnot do anything (the bbishop on g7 can't move because it prevents thee mate on h7).After 31.Kh1 Qh4 32. Rf1 Bf6 33.Rb7 Reg5 34.Qh3 Q:h3 black is better. But instead of 32.Rf1 white could try 32.Qg4 Q:g4 33.fg b4! 34.cb Re4 35.b3 R:b4 .
Premium Chessgames Member
  notyetagm: <AlexandraThess> I didn't mean an immediate ♔f1. The idea I saw on the other page was to play ♕h3 first to prevent ... ♕h4 and then play ♔f1.
Apr-24-06  monad: <notyetagm: Rybka eval >

I'll get on it for you today, in my lunch break.

Apr-24-06  monad: <notyetagm: Rybka eval > As promised:
Analysis by Rybka 1.1 32-bit:

1. = (0.63): 31.Kh1 Qg6 32.Rg1
2. = (0.00): 31.Rda1 Rd5 32.h4 Qxh4
3. = (0.00): 31.b4 Qh4
4. = (0.00): 31.Rb7 Qh4 32.Kh1
5. = (0.00): 31.Rc7 Qh4 32.Kh1

19 ply 2 hours

Apr-24-06  RandomVisitor: White's mistake in this game was 32.Rad7. Better was possibly 32.Kh1 and now if Rh5 33.Ra6! which is not possible in the Rad7 line actually played.

I agree with monad, after 31.Kh1 white stands better

Apr-24-06  monad: <RV>
I reckon it went back earlier even:

The White Queen had no need to place herself on -d7- in the first place. 30.Rd7 Rg8 poss. 31.Bd3 Ree8 32.Qb4 or something like that.

Not brilliant, but safe. And of course, Leko would not have been tempted to play the fatal Qh3.

Premium Chessgames Member
  notyetagm: Thanks for the evals, <RV> and <monad>.
Premium Chessgames Member
  notyetagm: Rybka eval please for the following critical position with Black to move from Yusupov vs Kasparov, 1989:

click for larger view

White has just played 31 ♘c3-d1. Here Kasparov played 31 ... ♘d3-e5 and went on to lose. What does Rybka say Black should play at move 31?

From the kibitzing page for this game:
< In his tribute to Kasparov in New in chess, Timman says Kasparov was easily winning with 31...Nxf4 (and, with more difficulty, still a move later) and suggests that Kasparov had pushed himself so hard early in the game that he lost energy at the end. >

Apr-24-06  RandomVisitor: After 31...Nxf4 32.Qxf4 Be5 33.Qd2 f4 34.Kg1 Qxh3 White has nothing at all.

The evaluation of -3.71 increases to mate in 17 (!) after Qxh3.

Premium Chessgames Member
  notyetagm: <RV> Wow, so the line beginning 31 ... ♘xf4! leads to a -3.71 eval and then to a mate in 17(!) after 34 ... ♕xh3.

So Garry really did miss out on a brilliancy prize. What a shame.


Apr-25-06  Rimrock: <Shajmaty> Check out
Apr-27-06  Shajmaty: <Check out; Thanks for the link, <Rimrock>. I was aware of most of these issues while helping a friend of mine programming a chess machine, back in 1994.
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