Author: Andreas Herrmann
Date: 10:27:26 12/07/02
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On December 07, 2002 at 06:55:39, David Rasmussen wrote: >In my incremental move generator, I first check if there is a hash move, and if >there is, then I check it for pseudo-legality. If it's not pseudo-legal, I >conclude that there is a hash collision. The position that this move was stored >from cannot be the same as the current, and still they have the same hash >signature. In my program when this happens, I exit. I do this because this >basically never happens. Until now. It was playing a game on ICC, and it >suddenly exited. I could see from the log that this is what happened. So I was >wondering: How often does this kind of collision happen for your engines? >I think Bob Hyatt has mentioned that this happens in 1 of 100 games. It doesn't >for me. > >/David Hi David, as far as i can remember in the papers of Dennis Breuker (http://www.breuker.demon.nl/thesis/index.html) you can find informations / statistics how often a collision can happen. In Holmes i uses a 63 bit signature and i store a hash age value. If the entry is to old i don't use it. I also check if the moves from the hash are legal before play them, but i havn't seen a collision now in many thousands of games. Holmes would beep in this case 3 times :) and write it to my log file that there was a hash collision. Andreas
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