Cheating chess computer

In 2011, the World Computer Chess Championship banned the four-time champion Rybka chess engine for cheating.

Chess pieces
che (Nolanus, Danny B.), CC BY-SA 2.5, via Wikimedia Commons

Yesterday I wrote about one of the first recorded instances of someone using a computer programme to cheat in a chess tournament. Today I wanted to write about the opposite: the time a chess computer programme was itself accused of cheating in a tournament specifically designed for computer chess programmes.

Firstly, I only just discovered that computer-only chess tournaments are a thing. They have in fact been running since at least 1970. The World Computer Chess Championship first ran in 1974. It pitted the world’s top chess programmes against each other. Who would be the top non-human chess player in the world?

That first year the Soviet chess engine Kaissa won. The chess computer arms race has continued since then, with ever more sophisticated programmes like the German “Shredder” and the Israeli “Junior” taking the title. Starting in 2007, the winner for an unprecedented four years in a row was the Rybka chess engine. But in 2011, Rybka ran into an unprecedented problem: it was accused of cheating.

How does a computer cheat at computer chess? Well, one of the rules for the World Computer Chess Championship is that the programmes must be original: you cannot use code from other chess engines. This is the rule in question:

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 the details of their submission form. 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.

Rules for the 18th World Computer-Chess Championship

In 2011, after four years of victories, officials of the International Computer Games Association (the tournament organisers) ruled that Rybka had plagiarised some of its code. Without attribution, this was a contravention of the rules. The chess engine was stripped of its four titles and banned from ever competing again.

Now, the question of whether the creator of Rybka actually cheated or not divided the chess computer world. Was it truly plagiarism, or did Rybka simply use a similar approach to other chess engines? You can read the back-and-forth in the third link below, if you really want to go down the rabbit hole.

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