Author: Uri Blass
Date: 13:39:58 02/20/02
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On February 20, 2002 at 13:10:01, Vincent Diepeveen wrote: >On February 20, 2002 at 09:19:20, Uri Blass wrote: > >sounds very buggy to me. > >easier is storing an array with hashcodes. goes very fast. >you can even skip step 2. > >what you do is pretty hard and not very smart IMHO. I agree it was not easy and I agree that hash tables are probably better but I wanted to get my program to participate in the 5th division of the winboard engines and one of the conditions was repetition detection. I did not want to copy from other programmers. I may change it later after I learn about using hash tables in chess programs but I guess that the speed difference relative to hash tables is not big and I believe that my program does not waste more than 1% of it's time in repetition detections(in most of the cases there is a conversion in the last 4 plies so I can detect no repetition with no problem). The main advantage of hash tables should be different then detection of repetition. some more details about my program: It generates only legal moves and for that purpose it builds attack tables that tells it for every square the directions that it is attacked and a pin array that tells it for every piece if it is pinned. Today it extends only positions when there is a single legal move or positions when the king is in check. It practically does not use today the fact that it generates only legal moves except the single reply extension but I may use my attack tables for the evaluation and for better search rules in the future. > >in the next line please tell me whether there is repetition: > >Ra1-a2 Rh7xh6 Ra2-c2 Kg7-h8 Kh1-h2 Kh8-g8 Rc2-a2 Rh6-h7 Kh2-h1 Rh7-h6 Ra2-c2 No repetition: taking back one ply every time sho that the last position did not repeat: Ra2-c2 white a2c2 Rh7-h6 Ra2-c2 white a2c2 black h7h6 Kh2-h1 Rh7-h6 Ra2-c2 white h2h1,a2c2 black h7h6 Rh6-h7 Kh2-h1 Rh7-h6 Ra2-c2 white h2h1,a2c2 Rc2-a2 Rh6-h7 Kh2-h1 Rh7-h6 Ra2-c2 white h2h1 Kh8-g8 Rc2-a2 Rh6-h7 Kh2-h1 Rh7-h6 Ra2-c2 white h2h1 black h8g8 Kh1-h2 Kh8-g8 Rc2-a2 Rh6-h7 Kh2-h1 Rh7-h6 Ra2-c2 black h8g8 Kg7-h8 Kh1-h2 Kh8-g8 Rc2-a2 Rh6-h7 Kh2-h1 Rh7-h6 Ra2-c2 black g7g8 Ra2-c2 Kg7-h8 Kh1-h2 Kh8-g8 Rc2-a2 Rh6-h7 Kh2-h1 Rh7-h6 Ra2-c2 white a2c2 black g7g8 Uri
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