Author: Ed Schröder
Date: 03:01:47 03/08/03
Go up one level in this thread
On March 08, 2003 at 04:21:25, Tony Werten wrote: >On March 08, 2003 at 03:43:20, Ed Schröder wrote: > >>On March 08, 2003 at 01:42:15, Robert Hyatt wrote: >> >>>On March 08, 2003 at 01:29:46, Joel wrote: >>> >>>>Hey All, >>>> >>>>Just wondering what everyone thinks is the best way to implement a pawn hash >>>>table? >>>> >>>>At the moment I am incrementally generating a seperate pair of pawn hash keys, >>>>and using them to index a table - very similar to how my transposition table >>>>works. >>>> >>>>Is it possible to do _significantly_ better than this? It seems to be somewhat >>>>expensive to do, although having said that my NPS still went up at least 20% in >>>>most situations. >> >>>That is what everyone since chess 4.x has done. Two signatures, one for >>>all pieces and pawns, one just for pawns. >> >>I don't use it, the problem is that you can not evaluate the coherence between >>pawns and the other pieces. If you have stuff like that in your eval pawn >>hashing is unusable and IMO that evaluation (coherence) is a must in a chess >>program. >One doesn't exclude the other. You can skip expensive "is this a >backward/passed/ouside passed/isolated/double pawn" tests if the hashtable >indicated that there isn't a backward/passed etc pawn on the file the pawn is >on. Of course I know that, but in case you have coherence code you should try it to combine with pawn-hashing and look at the troubles you get, if you are lucky you gain a few percent speed-up but end-up with a program that is very complicated to modify. Well, at least that was my experience with pawn-hashing, so I dropped it. I am not saying it can't be done, but if you have coherence code a major rewrite of the pawn stuff is needed, but maybe I have become just lazy during the years :) Ed >If there is and there isn't a double pawn on the current file then you can skip >all tests because you know it can only be the current pawn. > >Tony > >> >>My best, >> >>Ed >> >> >> >>> >>> >>>> >>>>I am not really worried about effeciency as much as some other people here, so I >>>>guess I am really asking whether I am missing something major. >>> >>>Doesn't sound like it. But you will end up storing more than just a score for >>>the position. IE passed pawn locations, weak pawn locations (or bitmaps that >>>feature them). Etc... >>> >>>> >>>>Regards, >>>>Joel
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