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.


Harvey Williamson's picture

He was invited to.

leigh's picture

Did he go?

MarkWatkins's picture

Rajlich was invited no less than 3 times (and probably more than that) to participate in the process. He seems to have indicated that he preferred not to take part in the Investigation, and thus for the Panel to produce whatever Report they did, whereupon he would then communicate directly with the Board. Upon completion of Panel proceedings and the final Report being written, Levy then made all the evidence available to him, asking him to comment. He largely chose not to do so.

Here are some snippets from various communications:

leigh's picture

How Jealous, jealous, jealous, jealous, jealous, jealous.......
In Chess, there is a tactics named deflection. You guys have no chance to use on the board, you used it here for taking the titles.
Now, Crafty is the No. 1 in the world; Fruits is the No. 1 in the world, Keep going to see who dare to beat me
Shame, shame, shame, shame, shame

I support Rybka......from today.

Michel83's picture

Well, I'll try:
So when the Rybka-team went around the Internet publically accusing other engines of being clones of Rybka (without ever presenting evidence), was that jealousy too? Since "now" you support Rybka it means you think THAT was totally ok? That would be a total double standard.

leigh's picture

Did I say Rybka was not jealous? No. Did I think Rybka was jealous? Yes.
That's not the point. The point is that Rybka occupied most of the chess engine market. Rybka earned a lot of money. Rybka beat most , not most, all of the engines which designed by the panel members. Let those people to decide if Rybka steals codes, even without thinking everyone knows the answer.
if Rybka steals codes, it should be very easy to find. it is not necessary to organize so many people and take so much time to analyze it.
from view of my point, ICGA should invite some programmers, I mean those programmers should understand all the computer languages that Rybka, Fruit and Crafty use. But they are not chess engine designers. Let them to decide if Rybka steals codes. it will make things fair.

Michel83's picture

Thanks for the clarification.

Don't get this as offense, but a post in which you only write "jealous" and "shame" 5 times in a row is rather annoying and not interesting- even more if you repost the almost same post a second time...reminding a bit of the average youtube-comment.
That's why I reacted.

But your last post above has "meat on the bones" (and whether one agrees with or not, it has a niveau and content that is a good base for a discussion). Thanks (honestly!)!

perham's picture

everybody who doubts the verdict should take a look at the evidence. I'm a computer science student and from what I understand, the evidence is really overwhelming and I guess Fruit's developers can go to the court with it, since he violated GNU GPL's terms.

Decembrist's picture

It is time:

Behind the reverse enginering of Rybka 3:

Head Comrade Yakov is Christophe Theron
Roberto Pescatore is Anthony Cozzie

Fellow decembrists now will speak out!

James White's picture

An interesting scenario is one in which essentially both Rajlich and ICGA are correct. If Rajlich implemented the primary logic of his program using machine learning techniques and trained it on the then-leading OSS chess programs then we would see exactly what ICGA found.

The question of whether that kind of "copying", in which the algorithm of another program is automatically reverse-engineered from its behavior, amounts to a violation of the ICGA rules is not entirely obvious. I would say though that it certainly seems to meet the "derived from" criterion because without the other program(s) then the "learning" algorithm will not function.

It is unlikely to violate US copyright unless the OSS licenses of Crafty and/or Fruit prohibit such usage - which AFAIK the GPL does not - (but IANAL). I have proposed the GGPL (Greater GPL) as a license to deal with exactly these sorts of issues for all types of metaprogramming programs.

The Devil's picture

Almost all strong chess engines seem to be partial clones of each other these days. One would not be surprised if the "cloning" tree extends all the way back to a much earlier engine, with each author borrowing from each other. To be honest, I'm not really surprised with Rybka. The fact it's being sold as a commercial engine is disturbing, but the fact that it's a clone doesn't really bother me.

DjPetrovic's picture

Vasik Rajlich is not a Serb and have no connection with Serbia. He has dual Czechoslovakian-American citizenship, and his wife is from Poland (where they live together).
This is 21st century. It is quite easy to google these things out.

hatsekidosie's picture

There are rumours that I myself am a clone. Or was it clown? Anyway, they say I plagiarize red noses, to which I reply other people with red noses just drink as much as I do: we come up with the same solution after intense calculations of misery and joy. Only 36 percent of our drinks differ.

hatsekidosie's picture

I would not call it plagiarism, I would call it a Ryb-off.

KevinB's picture

I don't want to hastily play armchair software copyright infringement juror, in this case. But, it's so intriguing.

Computer chess is suddenly extremely interesting, yet, even if this decision is entirely just, I can't help but wonder if it inherently devalues the title (CC champion)?

Presuming no future civil action is successful against Rybka, this coveted title would have been worn by a demonstrably inferior program (according to the CCC's own standards of measure, at the time), because -- what?! -- a Mr.Vasik Rajlich's bibliography was found wanting.

It's difficult to sell intellectual dishonesty to a public bent upon having the very best program (to enable their brilliant, uncredited kibitz work).

And, the sale is only more difficult, with people here suggesting Mr.Vasik Rajlich would be entitled to retain his titles, if only he'd disclosed that Rybka was 64% control-v -- with everything (from Claude Shannon, to Cray Blitz, to Crafty) all rolled up into an unscrupulous payday for wireless toilet riders.
[note to self: seek a copyright on slogan: "the right tool for anyone >96% primate."]

Might as well ban any chess program which fails to provide source code -- either openly, or perhaps to some special committee (a few members willing to sign NDAs, and act as judges)... The only trouble is, it then becomes the "Open Source Computer Chess Championship," and who needs this distinction?

Harvey Williamson's picture

This post i just found is a nice try to summarise things.

'I see a lot of assumptions and questions below about aspects of this case, so let me (as someone whose profession is in the software domain) attempt to offer some clarity from a code licensing perspective:

- Each piece of software is distributed under a certain license (of which there are many types) that the creator of the software decides on. The particular chosen license sets forth the rules of how the code and software may and may not be used, e.g., whether the code of the software is allowed to be reused/copied, and whether to do so requires attribution or payment. For software as an intellectual property, to not comply with the terms of a license is equivalent to stealing (from a legal perspective). So copying without attribution, in this case, makes the author liable for theft, at the least.

- That Rybka is superior in strength to the engines it has allegedly copied from is not surprising: it shows that more than copying has taken place, e.g., the application of some genuine creativity on the part of the creators of Rybka. That, however, does not mean that the copying is less of a violation, so the argument that it's better and therefore not exactly the same is moot; noone claimed that it's exactly the same, merely that portions of it are too much alike to be the result of mere independent creation coinciding by chance.

- The evaluation function is one of the most critical and distinguishing pieces of a chess engine; it's also the part that must be guarded the most if the author wishes to not be easily outdone. This is what makes some engines stronger than others. So copying the evaluation function is the same as grabbing the parts of highest value (without "paying" for them). As an analogy, if you visit a wine cellar and take away a $5 bottle without paying, the owner may choose to avoid the hassle of going after you, but if you took a vintage $5000 bottle away, they may be inclined differently.

- Whether we like or agree with the presence of licenses, especially restrictive licenses (like GPL, for those who know about it), is another point that has no relevance to the discussion. It's the author's choice what license to use, and it's their legal right to have their intellectual property protected from misuse under the terms of the chosen license. And yes, some licenses are generally preferable from the perspective of someone wishing to reuse code without too many strings attached (e.g., GPL isn't one of them).'

Morley's picture

Nothing about this over at Chessbase yet. Wonder why.

Crazylocha's picture

Freidric was a principle on this investigation/report. His holding back is commendable in allowing it to take off on its own. His restraint will probably result in a lengthy article soon. Hard for him to do an editorial report from his position fairly until it has had time to "season" a little. Also he has to rectify any legal contract issues with his Chessbase company and contracts with VS/rybka team before he publishes. Am sure there area few.sleepless nites andconference calls with lawyers, etc. before he can speak out.

Crazylocha's picture

Freidric was a principle on this investigation/report. His holding back is commendable in allowing it to take off on its own. His restraint will probably result in a lengthy article soon. Hard for him to do an editorial report from his position fairly until it has had time to "season" a little. Also he has to rectify any legal contract issues with his Chessbase company and contracts with VS/rybka team before he publishes. Am sure there area few.sleepless nites andconference calls with lawyers, etc. before he can speak out.

MarkWatkins's picture

To the best of my knowledge, Frederic Friedel, and the ChessBase news editor Albert Silver, only asked for access to the documents on the Investigations Wiki, and did not intend to be "Panel Members" (though these labels were deemed to be equivalent internally). Silver has since made clear that he would like his name removed from the Report as a Panel Member.

blueofnoon's picture

What the hell has happened?

I remember how Rybka team attacked other engines such as fire, ippolito, houdini etc for "pirating" their code.

But when somebody accused their own program for same reason, they decided not to defend themselves at all?

If that's really the case, I want the Rybka team to leave computer chess community forever, not just the computer world championship.

shahinjy's picture

I think all of chess players are cheaters when says "My 60 memorable games", my 100 best games and etc. All chess champions, GM, IM and etc are cheaters when says - my game. Actually theirs games based on the idea of Ruy Lopez, Petroff, Chigorin, Alapin and others who created, wrote and developed openings.

Arctor's picture

Your ideas are intriguing to me and I would like to subscribe to your newsletter

shahinjy's picture

If you think ICGA`s rule is right, then I think what i wrote above. It is sad.

Eiae's picture

Computer chess, who cares?

Anyway, Chess960 is the way to cure this disease engines have infected classical chess with. Let's get back to thinking over-the-board and have the best player win.

Tititi's picture

To me this is clear : During 4 years Rybka smashed all the programs out there. The other authors were JEALOUS of him. Fruit and Crafty are clearly insignificant compared to Rybka. If I write a piece of code , a "for loop" they will claim it'theirs. Those guys are loosers who can't stant comptetition.
If you can't beat his engine, take down the man. I will keep buying Rybka and ignore the other loosers.

Joe's picture

Please don't speak about programming since you don't know much about it. I am Software Engineer. Most Code is MOSTLY unoriginal and copied. Nobody wastes time reinventing the wheel. Also, search algorithms, tree lookups, comparisons are all similar code. This is the core of a chess program. These are solved problems. I've also viewed the evidence and as a Software Engineer is it NOWHERE conclusive. I can find similarities in similar programs at will. That doesn't prove plagiarism. I can take two Excel like programs and show that they do many things the same.

The problem like all things in chess are these petty, petty pathetic games played by chess institutions whether the FIDE, US Chess Federation, or Magnus/Kasparov revolting. They think that these institutions exist to serve themselves. NO! They exist to serve us the Chess playing public.

If I was ICGA I would be ready for a Libel lawsuit.

Despicableme's picture

Well , just remember how strongly they supported Kramnik with paper and computers for his bathroom during the Elista match...

Jack's picture

Hi Joe!

You create something and I will check it thoroughly and then improve it and call it my creation and prove it by saying that it is better than yours! :)

what do you say then?

max's picture

Joe's arguments are those of a Real Software Engineer :)

Bert de Bruut's picture

Chessbase has a problem as retail seller of Rybka. It is possible that the developers of Crafty and Fruit are going to ask compensation, now that Rybka has made good sales without proper acknowledging the contribution to its product by its rivals. Had Rybka for instance abided by the GPL license Fruit was under, then its source code would also have been open to competitors, and Rybka would never have dominated the market in the years 2007-2010 as it has done.

Despicableme's picture

ok, thx 4 the info.

Harvey Williamson's picture

The ICGA have created a page on Wikispaces

Here anyone can post ideas and proposed rule changes by clicking on the Discussion tab. You must 1st be a member of Wikispaces this takes about 11 seconds.

Only posts on this Wiki will be considered by the ICGA board.'

Wondering's picture

So what happens to all of the good work gone into later Rybkas,

it just gets flushed down the toilet? That's ridiculous.

Why wouldn't they encourage him to open source? Something.

It's obvious they don't really care about advancing computer chess,

it's all about money and egos.

And then Houdini takes things from Rybka. It's absurd, the whole thing.

Despicableme's picture

I cant see any article on chessbase about this , why is that?

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!

Martin's picture

Allthough I agree with Eiae that it's "just computer chess", it is slightly interesting. It seems to me that its all mostly build on circumstantial evidence. However overwhelming that may be, I'm by no means a legal expert or a computer-chess expert, but I'm having my doubts if that would hold in court. Is reverse-engineering accepted as evidence in court, for example?
Also, allthough it's highly suspicious that Rajlich doesnt defend himself, the burden of proof is on the claimant. Innocent until proven guilty, is one of the most important legal principles.

Martin's picture

Allthough I agree with Eiae that it's "just computer chess", it is slightly interesting. It seems to me that its all mostly build on circumstantial evidence. However overwhelming that may be, I'm by no means a legal expert or a computer-chess expert, but I'm having my doubts if that would hold in court. Is reverse-engineering accepted as evidence in court, for example?
Also, allthough it's highly suspicious that Rajlich doesnt defend himself, the burden of proof is on the claimant. Innocent until proven guilty, is one of the most important legal principles.

Lastly, Ive wondered if all would be well if Rajlich would just admit he copied parts of Fruit/Crafty and gave them credits according to GPL. Okay, Letouzey might want to see money, but I figure he could easily settle that for a small percentage and have his conscience cleared....

Ed's picture

I dont think it has been made sufficiently clear that the GPL is Viral (with all the advantages / and disadvantages that brings, i wont go into the merits here).

To admit that the source code contains portions of GPL code renders all the code GPLed, even your own creation. That, more than anything, might have been the reason for the initial and current reluctance to be more forthcoming?.

Martin's picture

Ed, there's always the option to pay for the use of the code. At least, I assume the original authors can sell their code to any license they wish. As I said, in this case that would come to a percentage of turnover/profit on the Rybka sales. But given the strength difference between the engines that shouldn't need to be a killer percentage.

Somrowsky's picture

Well, these news are quite shocking.

I checked the Chessbase website for a German report on these events, then I checked the English site and then the Spanish one.

The result was always the same: nothing. BACK IN THE USSR, or what? :)

chesscomputer's picture

is now rybka 4.1 multicore 64 bit freeware? i want download it for free?!

Nic the NZer's picture

I think it has become lost a bit that this has very little to do with the GPL license on the Fruit source code. The ICGA have decided that Rybka violated some of their regulations and so have asked for the return of prizes won as a result, and have banned Vasik Rajlich from competing in their competitions. Vasik Rajlich could have avoided this by correctly attributing all his sources when entering these competitions. It is my understanding that the regulation means you must attribute where you are copying source code, not the use of similar algorithms.

The ICGA has taken considerable trouble to find as much evidence as possible that Rybka incorporates the source code of other engines in it's make up. It did this before drawing conclusions and has also given Vasik Rajlich a chance to respond to the evidence given, or to defend himself by proving his innocence independently.

There is no problem with the GPL unless the FSF decides to prosecute in which case they would then need to prove the case themselves. There would probably be a different standard of proof in such a case anyway.

As any computer programmer can tell you a programs source code is rather like a novel in the following sense. Two people can independently write two books about the same subject and they might even have similar arguments to make. This does not imply that one book is copied from the other. In the same way two programmers might implement the same algorithm, but the source code written will be substantially different, as will the compiled version of this source code. It is virtually impossible for two programmers to write the same source code without copying.

hatsekidosie's picture

What if we'd forget about plagiarism and call it sampling of source code? A postmodern view on writing could do the trick.

John Jackson's picture

Let everybody 'steal' from each other with impunity, then let them compete with each other. What's wrong with this? - a no-holds-barred wrestling fight.

Joe's picture

I hope the ICGA is ready for a lawsuit. Libel is serious. If you read the reports they are very amateurish. They do not conclusively prove that he plagiarized anything. In fact, their own evidence by being circumstantial implies and admits that it is not an established fact, irrespective of the Institution "proclaiming" it so. If they had only said that they believe that it was plagiarism then it would have been an opinion. But they state it as a fact. Oh Noes!!

I think that the ICGA forgot that Rybka is a commercial product and so Vas's loss in reputation will result in massive damages. Can't wait to see how this will turn out.
How many millions Vas will win that is.

And for those of you who think the ICGA is correct, well, the best proof that Rybka is genuine is that it can BEST both Fruit and Crafty. It is substantially better. This is evidence that it is substantially different and is powerful evidence for a court.

kingspawn39's picture

I do agree with your argument, in theory; however, I cannot consider Rybka's superiority over Fruit and Crafy to be any evidence that Rybka is an original design.

For, Toga II is a direct clone of Fruit, and Toga II routinely outperforms the Fruit engine it was based upon. In addition, Strelka is a clone of Rybka's original free engine, Rybka 1.0, Yet, I do believe Strelka has outperformed that engine, too.

Rybka's dominance in the world of computer chess has been nothing short of spectacular. I sincerely hope Rybka is an original design.

Paul V's picture

I´m surprised that chessbase haven´t taken a more proactive role on this .

They are still selling the product with indirect reference to ICGA-titles:

"For years Rybka has been the uncontested number one in computer chess and since its great breakthrough in 2006 the program has won with remarkable regularity one world title after the other."

- I must say I find all of this quite detrimental to the chessbase brand.

gabriel's picture

Chessbase sucks!! Look at them. holding the information and only publishing what is in their own interest. They belong to another era, where information was totally controlled, more close to USSR or Nazi Germany. This is even more ridiculous in the internet era, where anyone can find the missing information in other sources, like chessvibes.

Philip's picture

and fruit is free


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