Author: Robert Hyatt
Date: 06:41:18 03/08/03
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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. Sure you can. You can evaluate all the pawn-only stuff, and then you can pre-cmpute whatever you need such as passed pawn locations, weak pawn locations, weak square locations, open file locations, half-open-file locations, and so forth. You stuff that in the pawn hash table, and then use it when you evaluate pieces to get the "coordination". I do the same thing for king safety which uses pawn structure as a major factor. But then piece locations, number of pieces, etc are folded in to the score using the pre-computed pawn structure values. I don't think _anybody_ evaluates pawns by themselves, except to recognize the classic weak pawns, but doing that saves time and pre-computing everything else saves more time. IE open files and weak squares for use in king safety. Open files for use in rook scoring. (weak pawns also). And so forth. I perhaps should have said "that is what everybody that does pawn hashing has done...." :) > >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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