Author: Robert Hyatt
Date: 20:46:42 11/01/98
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On November 01, 1998 at 13:47:18, Ernst A. Heinz wrote: >On November 01, 1998 at 12:56:12, Inmann Werner wrote: >> >>you are right. my percentage is about 50% in normal game. I have to think about >>it. >>On the one hand, if I make a hit, the evaluation is extremly fast. On the other >>hand, if I only hash the pawns, I get much more hits, but have more to do in >>much more difficult in evaluation, because good king standing and rook standing >>depends on pawn structure. >>When I have a little time, I try both and look whats really faster. > >Werner, > >All pieces that tend to move around *frequently* will greatly hurt the hit rate >of your Pawn hashing. Therefore, I recommend that you never include any major >or minor pieces therein. The Kings, however, are different "animals" which can >safely be hashed together with the Pawns as long as they must stay behind safe >shelters in the middlegame. "DarkThought" drops them from the Pawn hashing >*dynamically* as soon as King safety does not matter anymore. > >=Ernst= I did this in Cray Blitz, but believe that the current scheme I use in Crafty is far better. With the king included my hash hits were in the 90% range or so, while with it out, 99.9% is common. I looked at what I was doing, and it was mainly king safety related. And the king safety with the king at g1 is no better/worse than the king safety with the king at h1 or h2, if you only look at pawns. I now do normal pawn scoring, then king safety on *both* sides of the board, and store all this with just the pawn hash signature. When I want to evaluate king safety, I look at which side the king is on and start with that raw pawn structure score around the king... and then factor in other things (like is there a queen, how close are the pieces, are there open files with rooks on them around the king) and so forth.. I now get 99.9% hash hits which covers the king safety pawn structure... and there's no loss in accuracy of any kind...
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