Gilberto Rodriguez Orejuela, ‘El Ajedrecista’, died in prison in the United States on 31 May. The Colombian drug lord, a leader of the Cali cartel in the 1990s, acquired his splendid nickname, which translates as ‘the Chess Player’, on account of his ability to stay a step ahead of his rivals and pursuers.
Curiosity sent me hunting for more information, and in doing so I stumbled into an unexpected rabbit hole. For it turns out that ‘El Ajedrecista’ was also the name given to a primitive chess-playing automaton, designed by a Spanish engineer, Leonardo Torres y Quevedo, and unveiled at the University of Paris in 1914.
The ‘automaton’ label is closely associated with the ‘Mechanical Turk’, an attraction from the 1700s which appeared to play chess unaided, but actually contained a small but skilful human operator inside the large cabinet.
But ‘El Ajedrecista’ was the real deal, with electrical circuits and magnets and arms to move the pieces. By a curious coincidence, Fide, the international chess federation, was posting tweets about it on the same day that Orejuela died. This had nothing to do with the name, I believe, but was to advertise the fact that the rather beautiful contraption will be on display at the Fide Candidates tournament, which opens in Madrid on 16 June.
There was just one catch – it could only play one specific form of chess. It was designed solely to execute a mate with king and rook against a lone king, according to a narrow set of rules programmed into the circuitry.
Humans can accomplish this task without much difficulty, but to define a method precisely enough for a computer to execute is no easy task. The algorithm used by Torres’s machine seems to have worked like this:
1. Treat the a+b+c files, and the f+g+h files as separate ‘zones’. If the black king steps into the same zone as the the rook, move the rook to the opposite side.
2. When the rook is more than one rank away from the black king, move it closer by one rank.
3. Next check the position of the kings. If they are more than two ranks apart, move the king one rank closer, vertically. If they are exactly two ranks apart, count the number of files that separate them and apply the next rule
4a. If that number is odd, ‘wait’ with the rook, e.g. move from a5 to b5 or h5 to g5.
4b. If that number is even (and at least two), move the white king one file across, toward the black king.
4c. If that number is zero (that is, the kings face each other), advance the rook one rank to give check. Eventually, this will be mate!
The diagram shows a pretty favourable starting point, and my computer indicates that mate could be achieved in just 11 moves. By contrast, following the recipe above seems painfully slow, but it does get there in the end. Black’s moves were chosen by me, while White’s moves were chosen by applying the recipe above.
1 Ra6 Rule 2 Kd7 2 Kb5 Rule 3 Kc7 3 Rh6 Rule 1 Kd7 4 Kc5 Rule 4b Ke7 5 Kd5 Kf7 6 Ra6 Rule 1 Ke7 7 Rb6 Rule 4a Kf7 8 Ke5 Rule 4b Kg7 9 Kf5 Kh7 10 Kg5 Kg7 11 Rb7+ Rule 4c Kf8 12 Kg6 Rule 3 Ke8 13 Kf6 Kd8 14 Ke6 Kc8 15 Rh7 Rule 1 Kb8 16 Kd6 Kc8 17 Rg7 Rule 4a Kb8 18 Kc6 Ka8 19 Kb6 Kb8 20 Rg8 Rule 4c checkmate
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