Author: Uri Blass
Date: 08:33:10 07/12/02
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On July 12, 2002 at 09:58:15, José Carlos wrote: >On July 12, 2002 at 09:52:03, Ricardo Gibert wrote: > >>On July 12, 2002 at 09:27:43, José Carlos wrote: >> >>>On July 12, 2002 at 09:19:10, Richard Pijl wrote: >>> >>>><snipped irrelevant part> > >>How should this next position be handled? >> >>[D]8/6k1/1b6/2p5/3pP3/3P4/1B4K1/8 b - e3 0 1 >> >>White has just played e2e4 and the reply de3 e.p. is not a legal move. Should >>this position recur, is it counted as a repetition since the same set of legal >>moves for Black are available? Either way, do programs handle this case >>corrrectly? > > According to Richard quote >*** >"Positions as in (a) and (b) are considered the same, if the same player has the >move, pieces of the same kind and colour occupy the same squares, and the >possible moves of all the pieces of both players are the same." >*** > I understand possible moves = legal moves, so it should be considered a >repetition. As for chess programs, I'm afraid most won't handle it correctly, if >not all, because you would have to test if de3 is legal in the moment you're >deciding whether e3 is an ep square or not. > > José C. Movei has no problem here because it does not use hash tables to detect repetitions. Movei's repetition detection is wrong but not in this case. It assumes that it is repetition if the same pieces are in the same square and the side to move is the same. Using hash tables may do movei slightly faster in detecting repetitions but I prefered not to do it until today because I am afraid from more serious problems and there are more important things to improve in movei. Movei never suffered from wrong repetition detection in games and it played more than 1000 games so I did not consider the problem as an important problem. Uri
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