Rybka, the best chess-playing computer program in the world and the winner of the last four World Computer Chess Championships (WCCC), has been disqualified and banned for the plagiarizing of two other chess engines, Crafty and Fruit.

In a damning missive, the president of the International Computer Games Association (ICGA), the governing body behind the WCCC, describes how the author of Rybka, Vasik Rajlich, “unfairly” cheated his way to four victories by ripping off the work of other chess masters. The ICGA is demanding the return of both the trophies and the prize money, and has revised the standings of the last five championships to reflect Rybka’s excommunication. Not since IBM’s Deep Blue cheated to beat Garry Kasparov in 1997 has the world of computer chess been so uproarious!

The ICGA’s entire case seems to hinge on Rybka’s similarities to Fruit, an open source chess engine that was the runner-up at WCCC 2005. Rybka debuted the year after, and from the get-go experts were claiming that Rybka evaluated moves in an identical fashion to Fruit. Curiously, ICGA isn’t even disqualifying Rybka because it copies Fruit — rather, it’s simply upset that Rajlich claims his engine is original, and refuses to give credit where it’s due.

To come to this rather epic and libelous conclusion, the ICGA assembled a 34-person panel of programmers who have competed in past championships to analyze Rybka. Unfortunately, Rybka’s source code has never been available, so reverse engineering and straight-up move-evaluation comparison was used to analyze the originality of Rajlich’s chess engine. The panel unanimously agreed that newer versions of Rybka are based on Fruit — and worse, that the early beta versions were based on Crafty, another open-source chess engine. Rajlich has always claimed that Rybka is original — even when confronted with the findings of the report by the president of the ICGA.

Vasik Rajlich, incidentally, is an international master himself, and a graduate of MIT. Spectrum has a fantastic analysis of his background as both a brilliant chess player and an engineer — and it leaves you wondering if Rybka’s disqualification is actually kosher, or merely the result of a witch hunt. After all, with Rajlich not making his source code available, it’s almost impossible for the ICGA to be sure that he ripped off Crafty and Fruit — but at the same time, it’s easy to see the allure of the open-source, world championship runner-up Fruit.

If Rajlich did plagiarize Crafty and Fruit, the reasons are probably financial: Rybka is a commercial piece of software, and its accolade as the best chess program in the world must surely bring in a few dollars. It’s a tricky situation, though: with Rybka now outlawed from the WCCC, and with the ICGA asking other tournaments to block its entry, the only real way Rajlich and the rest of the Rybka team can clear their names is to show their source code — a financially untenable move. In short, Rybka is stuck between a rock and a hard place.

Read more at ChessVibes or download Rybka

[Image credit: thrig]