Author: Will Singleton
Date: 11:56:45 06/13/04
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On June 13, 2004 at 14:54:24, Will Singleton wrote: >On June 13, 2004 at 14:24:57, GeoffW wrote: > >>Hi >> >>I was thinking how I would add pawn hashing to my program. Having read a little >>of the Crafty source I have a rough grasp of the idea, however there are a >>couple of things I am hazy on. >> >>Q1) >>I understand the pawn hash score stored must not contain any piece related >>scoring as that must be factored in later. In my program even the simple choice >>of which pawn position look up table is determined by the phase of the game, i.e >>it will be piece dependent. How would I get over that obstacle ? Score the pawns >>for end game, opening and middle in the hash, and choose which one to use later >>? >> >>Q2) >>Crafty uses an 8 bit bitmap to store file for passers, this is ok for a bitboard >>program as it is probably trivial to find the exact location later. However for >>a non bitboard program it is non trivial to find the exact locations. Do I have >>any alternative but to store the passer locations in the hash ? That would be 16 >>bytes just for the passed pawns for both sides? >> >>Hope my questions made sense I typed them quickly as the England match is about >>to start, must dash ................... >> >>Thanks for any help >> >> Regards Geoff > >I don't know if my implementation is best, probably not. Testing shows it works >ok. I adjust the hashkey by the castle status, king positions, endgame flag, as >well as piece count and material value. So, any factor that might affect the >pawn scoring, that isn't accounted for elsewhere, will be allocated its own >position in the table. > >Since we've got a lot of memory to play around with, and the pawn table doesn't >have to be big to yield its max benefit (which isn't much anyway), I store tons >of stuff in the table. Passed pawn arrays, number of passers, pawn holes, pawn >blocks, etc...
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