Author: Peter McKenzie
Date: 13:10:21 07/17/00
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On July 17, 2000 at 13:40:28, Tom Kerrigan wrote: >I've had a number of requests to implement 3-fold repetition detection in TSCP. >It's also clear that TSCP would do better in tournaments (although that isn't >the goal...) if it could detect these draws. > >So the question is, is there an easy way to do the detection? > >In my "strong" program, I just compare hash keys. But TSCP doesn't keep hash >keys and I have no intention for it to do so. So is there another way to do it? > >Thanks in advance. > >-Tom You can do a simple version of repetition detection that catches short repetitions by just looking at the last few moves. For example, consider the repetition (from start position) 1.Ng1-f3 Nb8-c6 2.Nf3-g1 Nc6-b8 3.Ng1-f3 Things to note about this sequence of moves: 4 reversible moves in a row (no castling, captures or pawn moves), your 50move code should keep track of this. The first move in the sequence could have been a capture. To square of last move = to square of move at ply-4. From square of last = to square of move at ply-2 To square of move at ply-1 = from square of move at ply-3 You can extend this logic to handle longer sequences without too much pain. I guess if you generalise it totally you end up with something like what John Stanback posted. cheers, Peter
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