Reports | June 29, 2011 8:42

Rybka disqualified and banned from World Computer Chess Championships

Rybka disqualified and banned from World Computer Chess ChampionshipsThe International Computer Games Association (ICGA) has disqualified and banned Rybka and its programmer Vasik Rajlich from previous and future World Computer Chess Championships. The ICGA accuses Rajlich of plagiarizing two other programs, Crafty and Fruit, and demands that he returns the trophies and prize money of the World Computer Chess Championships in 2007, 2008, 2009 and 2010.

For quite a while there has been some serious turmoil in the computer chess world. When we reported about the Houdini-Rybka match in February of this year, the article triggered lots of comments about the issue of cloning. Was Houdini derived from the Ippolit series? Was it plagiarized from Rybka? And what about Rybka, was it largely based on the code of other engines? Nine days later we published an article by IM David Levy, President of the International Computer Games Association (ICGA), who shared his thoughts about how to tackle the issue. A few days later he announced the establishment of the ICGA Clone and Derivative Investigation Panel. Not long after, on March 1st, we received an open letter about the Rybka-Fruit case signed by fourteen chess programmers. They all supported the claim that Rybka was cloned from Fabien Letouzey’s Fruit. In the last few months all the allegations have been seriously studied by the International Computer Games Association (ICGA). On Tuesday night we received the following text from the ICGA President himself.

Rybka Disqualified and Banned from World Computer Chess Championships The International Computer Games Association (ICGA) has been conducting an investigation into allegations that, in the chess program Rybka, the programmer Vasik Rajlich plagiarized two other programs: Crafty and Fruit. The ICGA has considered and evaluated the evidence presented to the investigation panel and the report prepared by the panel’s Secretariat. (The report and evidence files are attached.) We would like to thank those members of the panel who contributed to this investigation and the Secretariat for the enormous amount of conscientious work they have put in to this matter. By a unanimous 5-0 decision of executive members of the ICGA we find ourselves in agreement with the verdict of the Secretariat’s report. We are convinced that the evidence against Vasik Rajlich is both overwhelming in its volume and beyond reasonable question in its nature. Vasik Rajlich is guilty of plagiarizing the programs Crafty and Fruit, and has violated the ICGA’s tournament rules with respect to the World Computer Chess Championships in the years 2006, 2007, 2008, 2009 and 2010. Specifically, Vasik Rajlich, on all five occasions, violated Tournament Rule 2 which requires that: Each program must be the original work of the entering developers. Programming teams whose code is derived from or including game-playing code written by others must name all other authors, or the source of such code, in their submission details. Programs which are discovered to be close derivatives of others (e.g., by playing nearly all moves the same), may be declared invalid by the Tournament Director after seeking expert advice. For this purpose a listing of all game-related code running on the system must be available on demand to the Tournament Director. By claiming other programmers’ work as his own, and failing to comply with the abovementioned rule, Vasik Rajlich has unfairly been awarded one shared 2nd-3rd place (in 2006) and four World Computer Chess Championship titles (in 2007, 2008, 2009 and 2010). Furthermore, it seems to the ICGA that Vasik Rajlich clearly knew that he was in the wrong in doing so, since he has repeatedly denied plagiarizing the work of other programmers. The ICGA regards Vasik Rajlich’s violation of the abovementioned rule as the most serious offence that a chess programmer and ICGA member can commit with respect to his peers and to the ICGA. During the course of the investigation and upon presentation of the Secretariat’s report Vasik Rajlich did not offer, despite repeated invitations from the ICGA to do so, any kind of defence to the allegations, or to the evidence, or to the Secretariat’s report, other than to claim in an e-mail to myself on May 13th 2011 that: Rybka has does not "include game-playing code written by others", aside from standard exceptions which wouldn't count as 'game-playing'. The vague phrase "derived from game-playing code written by others" also does not in my view apply to Rybka. The ICGA is of the view that such a serious offence deserves to be met with correspondingly serious sanctions against the perpetrator. In deciding on appropriate sanctions the ICGA has borne in mind the approach of the International Olympic Committee for dealing with the most serious cases of the violations of its rules. The ICGA has therefore decided as follows:

  1. Vasik Rajlich is hereby disqualified from the World Computer Chess Championships (WCCC) of 2006, 2007, 2008, 2009 and 2010.
  2. The 2nd-3rd place awarded to the program called “Rajlich” in the 2006 WCCC is hereby annulled, sole 2nd place is awarded to the program Shredder, and 3rd place in that event is awarded to the program Zappa.
  3. The 1st places and World Computer Chess Champion titles awarded to the program Rybka in the 2007, 2008, 2009 and 2010 WCCCs are hereby annulled, and all the other programs that competed in those events are moved up in the final tournament standings by one place. Thus the revised tournament standings and titles for those events will now be as follows. 2007 1st Zappa (World Champion) 2nd Loop =3rd GridChess =3rd Shredder 2008 1st Hiarcs (World Champion) 2nd Junior 3rd Cluster Toga 2009 =1st Junior (Joint World Champion) =1st Shredder (Joint World Champion) =1st Deep Sjeng (Joint World Champion) 2010 =1st Rondo (Joint World Champion) =1st Thinker (Joint World Champion) 3rd Shredder
  4. In due course those programmers whose programs have been elevated to World Champion (or joint World Champion) status will receive from the ICGA replicas of the Shannon trophy for the appropriate years.
  5. The plaques on the Shannon trophy that currently bear the name Rybka (for the years 2007-2010) will be removed from the trophy and new plaques will be engraved with the names of the revised winners of the title.
  6. Similarly, the titles of World Computer Speed (Blitz) Chess Champion that were awarded to Rybka in 2009 and 2010 are hereby annulled. The revised winners of the speed chess title for those years are therefore: 2009 Shredder 2010 Jonny and Shredder (joint champions)
  7. Vasik Rajlich is banned for life from competing in the World Computer Chess Championship or any other event organized by or sanctioned by the ICGA.
  8. The ICGA demands that Vasik Rajlich return to the ICGA the four replicas of the Shannon Trophy presented at the World Computer Chess Championships in 2007, 2008, 2009 and 2010, and to return to the ICGA all prize money awarded for Rybka’s performances in those events.

David Levy [President - ICGA] June 28th 2011

Mr Levy also sent us a big number of documents which according to the ICGA form the evidence to the claim that Rybka was plagiarized from Crafty and Fruit. These documents can be downloaded below for anyone who wishes to dive further into the material. The news is obviously a huge blow for the Rybka team. The impact in the computer chess world must be comparable to arguably the most famous example of doping in athletics: the positive drug testing of Canadian sprinter Ben Johnson in 1988. We've asked Vasik Rajlich for a comment and hope to add this later.


Peter Doggers's picture
Author: Peter Doggers

Founder and editor-in-chief of, Peter is responsible for most of the chess news and tournament reports. Often visiting top events, he also provides photos and videos for the site. He's a 1.e4 player himself, likes Thai food and the Stones.


Andres's picture

Funny how Chessbase has not cover the story at all.

brianinski's picture

It would have only taken the polite courtesy of naming the code authors? Just goes to illustrate how a lack of integrity catches up with people. The plagerizer pretending to create Rybka solely by himself, must feel like an idiot!

I wrote to Chessbase and asked Fredrich to join the discussion, yes I found it curious that they seemed unwilling to hinder sales with an admission they were promoting plagerized creative content/someone else's intellectual property.

Peter's picture

The ICGA can prove that code from crafty or Fruit ( I forget which) exists in Rybka 1.0 and through to Rybka 2.3.2a. They would have to be really stupid to accuse someone without being able to prove it and also be advised that legally if sued they would win. Some months ago V Rajlich began talking about renting out powerful Clusters for rybka which would stop any more re-engineering of the Rybka code and i think from what i read its a success. So i don,t think after whats happened now he will create a Rybka 5.and i'm pretty sure he won.t be bothered either. We will continue to receive Houdini updates for free. So Rybka was good while it lasted but i think this is the end of the road for Rybka.

Nico's picture

From another perspective, whilst Rybka may have been the strongest PC chess program, is it actually worth very much? Serious chess that requires heavy lifting like Rybka programs is a minority pursuit, and it is copiously pirated anyway. Is there enough money to sue for? And who of the open source community could put the money together to sue them? I agree it would be a good demonstration of the strength of the GPU licence in court, but I have the feeling this instead will fizzle out with Chessbase making a small payout.

vasline's picture

Gimme me the code and I will create Rybka360. ;-)

It's the end for Rybka.....When I heard people talking about Rybka 5.......It's it a joke???????

And people pay for a non recognize software.....ahahahahahahahahahahahaha

rajlik's picture

You are right my friend.....

Paul V's picture

New interview with Vasik Rajlich:

regards, Paul

vik's picture

The fact is that me as a customer is disappointed, since i was a Rybka 1 series customer especially.

This is a shocker actually !!! he was hiding this all these years omg

kingspawn39's picture

Rybka's a fine chess engine. It has managed to meet all of the qualifying standards of many testers. Suddenly, it's a clone.

pradip's picture

when i first time heard about Rybka, i was comfused whether i would work or not but now i think that you are right.

for more information:

Joshua Perry's picture

Wow! Two programs with exactly the same specs using the same programing language have similar code! That never happens!

Obvioulsy, either the folks doing the investigation don't understand anything about programming and compilers, or they have a motive to take adverse action against a better programmer. I'm guessing the latter since they were able to dissassemble the code.

What's the easiest way to beat the top guy? Have him labeled a cheat and removed from competition. If it's the same code, and you only need to give credit, how come the rest of the programmers didn't use the same code and have as good a program? Oh yeah, because it's not the same code and Vas is a much better programmer.

What a shameful attack...

Franco Martel's picture

remove Rybka is unfair, but use the codes of fruit and crafty, there is a difference between the performance of Rybka and his predecessors. Remove titles Rybka, but rather responds to interest from other participants that l title. What is that Rybka just stay with your crown and share the credit and he gave with the other programmers Fruit and crafty.

Gangtrag's picture

I think the biggest problem in the Fish that she used the original model which says that any move in chess, there is only one right decision and no matter how much you do not try to do differently in a perfect game will always be one solution it follows that in the foreseeable future, the overlap all programs will be above 70%

Gangtrag's picture

And yet people who took out the decision in terms of ordinary mathematics idiots. The best idea is not to Fish estimates the position itself but the ability to cut off the options that have no counter-play (the same as it was unable to Fruit of the proper degree) The fish was so long the world's first only because all the other programs could not play any arbitrary position with many figures in the middle of the party. Rajlich made perhaps the simplest and yet most brilliant thing he did not fooling myself with writing positional tables calculate the strong and weak fields, and positional advantage here because the evaluation of Fish and coincides with Fruit (yes this is a table of these programs are almost identical to what I 99% sure but they are also identical in any book on chess theory) So, let's find the first printed book on chess theory and has sued for plagiarism and other authors Fruit chess programs (left to find the heirs of the author of this book and in the bag)

Rei's picture

Wow its amazing the comments here to me from almost all who have clearly not read the evidence and reports all which can be downloaded and viewed here:

It took me a couple of hours to read all get the full set of facts but even if you read the summary in the Rybka_Investigation_report.pdf you will VAST AMOUNTS of clear evidence of stolen code and if it matters to anyone I am have been a programmer for almost 20 years.

But if you are still inclined not to get the facts and make judgement quickly heres a couple key points IMHO:

The pre-releases of Rybka contained large amounts of identical obsolete code that was in Crafty. Obsolete/Dead code is in fact that, its a bunch of code that was written, never used but somehow was not removed.

The early Rybka versions have a sequential, numerical and in many cases verbatim comments to that of Fruit 2.1.

The chances of someone leaving the same dead code or writing a comment like:

//this line is a hack, its crappy but so is UCI

where to code and algorithms match others code is not remote is impossible.

And FYI, the way this was obtained was by using something called a dissambler/de-compiler which are programs that essentially take programs that computers run which are zeros and ones/binary and generate source..again the chances of even getting the same output from ones of these is remote.

As a programmer, this was not shameless it was a crime.

Gangtrag's picture

There is such as macros, my friend, and now no one programmer to write software from scratch will not (this makes no sense unless the loss of nerves and time) you casually read the report and yet there is clearly stated that the match is 30-40% in all engines (then if you follow the letter of the law all the thieves)

Rob's picture

I honestly don't think you are *older* than 20 with all the incoherence and the spelling and grammar errors. I'm not really sure what kind of "programming" you've been doing, certainly programming remote controls don't count. This is a much exaggerated view of the matter. Taking low level implementation from other people and using it as abstract tools is a common practice in programming and engineering in general. Nobody writes programs while thinking about the electrons in the semiconductor devices. Although really, they should, using your logic. Because otherwise they would be "stealing" the concepts from electrical engineers/ systems engineers/ operating system engineers, etc. Right? It's not right to "use" other people's CPU, you should make your own and think of the electrons as they move and try to program that! This is your argument.

Programming is a hierarchy of abstraction. Nobody builds __anything__ from scratch. Just as no one thinks about electrons, no one thinks about circuitry of motherboard and logic gates in the CPU, no one really thinks about assembly instructions and registers, no one really thinks about operating system code and kernel, and certainly no one thinks about low level code that exists in C or other kinds of libraries that makes the applications do what they do. Programs __always__ build on top of other programs. It has been that way since the dawn of time.

I believe Rybka is a genuine case of a chess program that was built "on top of" not "derived from" other MUCH MUCH WEAKER engines. Clearly, neither Crafty nor fruit have made it even close to the top 10 engines in the world. They are, and have clearly been, more or less envious of Rybka's tremendous success, and while they can't think of any way to be productive or positive, they want to belittle/blame/degrade Rybka to make themselves feel better. Perhaps they have the dream of sharing Rybka's success, although they take trivial part in it.

Vas deserves the credit for taking the awfully weak, yet highly potent open source engines and creating what could be called an Artificial Intelligence masterpiece. He has clearly come up with much better heuristics than the two weaker engines, much more improved pruning and search, better data structure and memory management, and probably much higher level abstract code. Rybka dominated computer chess for half a decade due to Vas' genuine contribution. Today, engines that are of comparable strength are arguably built "on top of" Rybka. An obvious example is Houdini.

Why isn't anyone blaming Houdini for ripping Rybka off and taking its code and improving it, now charging people for its newer 2.0 version? And why isn't anyone going through the list of all 600 or so engines and perform the same tests they performed on Rybka with the same kind of precision and exhaustiveness to see if they are, in fact, derived from other engines?

This whole decision of ICGA comes across to me as a hesitant and not-well-thought-out decision on part of the directors of their board. How can they decide the merit of a case without allowing any defense from Vas, charging the maximum penalty with such fury and speed? It's almost like they were paid to delete Rybka from their lists. They should seriously consider to reverse their decision. If I was Vas, I would take no time in appealing the ICGA's decision.

Also, Vas should probably admit, if he is utilizing any, if at all, parts of the source code he used that was originally provided in Fruit of Crafty. This is a first step.

nereza's picture

Your long eulogy of Rybka is simply ridiculous. It is now a proven fact - the guy who programmed Rybka reused big portions of code from other chess engines without any alterations or with just minor ones. Period. We are not talking about common programming algorithms or well-known data structures and abstractions - it is about blocks of source code, copy and paste.
And the thing that this engine is allegedly much better than the ones it copied has little significance if at all. These open source chess engines were created without any commercial idea, and you can imagine that the authors have to do something else for a living. Then some smart "businessmen" comes, commercializes the whole thing, starts making money from it and of course he will have both the time and resources to greatly improve the code that he originally stole. There are two things in that - the first one is the legal side of the story. The copied open source engines were released under a certain open source license - in this case GPL. This license stipulates that their code can be reused but under certain conditions. In the case of Rybka there is a clear infringement of this license. An example here - Internet Explorer, the famous browser until recently had an explicit mentioning in its license information that it contains portions of the code of a prior browser called Mosaic. Well, may be very few have heard about Mosaic, 'cos it was popular only in the very early years of the internet, but still Microsoft honored their legal obligation and recognized the presence of prior effort in their popular product.
The second side is the moral one. This guy Vas simply capitalized on the efforts and achievements of others, lied for years denying that and didn't even bother to acknowledge the fact that his engine was a success only because it was based on certain open source engines created by other people. What a schmuck.

Gangtrag's picture

And the remains of dead code is a surplus just a macro and not plagiarized as you think (

DM's picture

One cannot argue with Rybka's results.
Rybka won several years in a row.
There are claims that Rybka is substantially the same as Crafty and Fruit.
If this were true I would expect Fruit and Crafty to place relatively close to the first place finisher - Rybka.

So people are claiming that these programs are substantially the same and the results are very different.

I think a more independent review should be conducted.

Grats Rybka on your results.
These allegations should not tarnish your results.
This isnt an issue of doping.
The code was written, the computer followed it, and it beat other computers that also were following code.

If I write a windows program do I need to write a menu bar from scratch or do I use a menu bar control that others wrote and if I do - does it take away from whatever I achieve with the program.

Chess programs share pieces like menu bars.

We are here because we have a love for the game.
Lets not take away from the accomplishments of Rybka.
Not unless all programs are going to be subject to the same review.

cod fish's picture

hug your code and sleep

Mauricio Valdes's picture

Rybka is the Danailov of chess engines!

Rob's picture
soidog's picture

rybka is disqualified from world computer chess championships on a technicality but that does not mean that vasik radlich has not made a significant contribution to computer chess. although rybka may in fact contain plagiarized code or algorithms from fruit or crafty does anyone seriously think that these engines are in the same league with deep rybka? i ran a 3-way 10-game round robin tournament among deep rybka, and the latest versions of fruit and crafty and the results are: rybka 20/20, fruit 7.5/20 and crafty 2.5/20. so my advice to radlich is kiss the world championships goodbye and just keep up the good work and continue to work on the speed of rybka (slow compared with houdini3) and thank you for a find product. if you can produce the best engine there is the world will beat a path to your door world championships or no world championships. in fact if everyone agrees that rybka is the strongest engine and the world championships are held sans the strongest engine it is the world championships and not rybka that will become irrelevant.


Latest articles