Author: Don Dailey
Date: 11:07:25 06/20/98
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On June 20, 1998 at 13:02:54, Robert Hyatt wrote: >On June 20, 1998 at 11:30:01, Stuart Cracraft wrote: > >> >>> >>>1. This shoule *not* be a compute-intensive task. If you aren't yet hashing >>>your pawn structure scoring, you should, because whether a pawn is passed or not >>>is a static piece of information that is independent of other pieces. If you >>>hash this, you will find that you find over 99% of your pawn structure >>>evaluations are not needed because after you compute them one time, you will not >>>re-compute this again, just use the hashed value. >>> >> >>While what you say is true about the 99%/1%, passed pawns that are >>carefully calculated are not hashable. The reason is that a good calculation >>of a hashed pawn includes who controls its queening square and >>who controls the square directly ahead of it (facillitating its advance) >>as well as other attacks along its path as well as blockading enemy pieces >>on that path that would impede its progress. These extra items involve >>calculations related to non-pawn pieces and therefore may be in >>different positions where the passed pawn is on the same square. Hence, >>unhashable. If you take the trivial case of just hashing the fact that it is >>a passed pawn, then yes, that is hashable. But not the full case which >>is what you really need. >> > > >But if you read his post *carefully* he was talking specifically about the >case of *recognizing* passed pawns, not *evaluating* them. This is only >dependent on the positions of enemy pawns, and the effective cost of this >is always *zero* with hashing. What you do with that information later is >another issue, but not the recognition phase. Stuart, Don't you keep information in your pawn structure hash table? I don't even return a score, I simply calcuate all the important pawn things I can and then, like you, evaluate them later. For instance I have a list of passed pawns. I identify them and nothing more. I have bitboards telling me which squares can never be attacked by pawns and I identify backward pawns. In the evaluation I test for things like occupying a square in front of a passed pawn or in front of a backward pawn, things I cannot do in the pawn structure table. Why should I have to recalculate this again? - Don
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