Author: Aivaras Juzvikas
Date: 11:57:54 06/13/04
Go up one level in this thread
On June 13, 2004 at 14:47:42, Andrew Williams 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 >>? >> > >What I do is to hash in the game stage as well, so I could end up with three >separate entries in the pawn hash table for the same constellation of pawns. > does it pay off?i mean without stuff like that u get 99% pawn hash table hit/try ratio, and with game stages i guess it should be much less?even adding ep square (which isnt needed in my case coz it doesnt affect pawn evaluations) reduces success by 1% (only tested in opening positions) >>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? >> > >If store two 8-bit words for each of: > passers > candidate passers > weak pawns > >When I grab the entry from the table, I find the relevant pawns by walking up >the relevant file. I've not looked at crafty's approach, but it sounds like it's >the same. > >>Hope my questions made sense I typed them quickly as the England match is about >>to start, must dash ................... >> > >Me too!! > >Andrew
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