Author: Robert Hyatt
Date: 07:40:41 07/20/99
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On July 20, 1999 at 02:20:03, Scott Gasch wrote: > >Ok, I've heard people talking about pawn hash tables and this got me thinking >about them. I am not sure how to do it -- > >1) if you just hash 8 pawn locations and an associated evaluation that is pretty >easy. It's a nice small number, can fit in memory, etc... However, you can't >recognize passed pawns becasue you don't know where the enemy pawns are? > hash all 16 pawns into one signature... then this isn't a problem.. >2) if you make a table with all 16 pawns in all possible configurations I >calculate a total of 1120853258472 possibilities. That requires quite a bit of >memory... ;) you will find most of those don't really occur... and in a good chess engine, pawn advances are treated cautiously because they permanently affect pawn structure and most programs weigh this heavily. I usually see a 99% hit rate on pawn hash probes, for example... This means that only 1% of the positions need a full pawn-structure analysis. So that I can put _anything_ in the pawn structure analysis I want since it costs essentially nothing. > >3) do you mean just hash the recent scores for pawn structures? This way any >node that has the same pawn structure anywhere in the tree can get the pawn >score instantly? > yes... >Thanks, >Scott
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