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Subject: Re: Pawn Hashkey Size

Author: David Rasmussen

Date: 04:33:08 12/04/01

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On December 04, 2001 at 04:30:03, Sune Fischer wrote:

>>
>>In the exact same test, Crafty gets similar results. 115 collisions in 3
>>minutes, but at a search-rate of 137kn/s compared to my 450kn/s. So at this
>>rate, Crafty would get about 3-400.
>>
>>/David
>
>Are you sure this is a pawn hash table only?
>I can believe these numbers if they are for the standard hash, but it doensn't
>sound right for the pawns.
>

Of course I'm sure. It's pretty difficult to mess that up, since the trans/ref
table and the pawn hashtable in Crafty used very differently.

What I have done in the test is exactly this:
In EvaluatePawns(), whenever I get a hit in the beginning of the function,
Crafty would usually return with the values from the table, but I don't. I just
remember that there was a hit, and the score that came with it. And now, I am
only talking about the final score value, not the pawn structure properties that
Crafty also stores in the table. If I checked on those too, there might be even
more collisions.
At the end of the function, the score has been calculated, and I check if there
was a hit at the beginning. If there was, the score (and other data, which I
don't check) from the pawn hashtable, better be the same, or else we have a
collision. We might have even more, but we definately have these. I just count
these collisions, and print them out. Very simple, and it proves without doubt
that "damaging" collisions do happen, and fairly often. They might not be
damaging after all, since there are relatively few of them overall, but still,
the rate of collisions are very much like what I see with my program.

/David



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