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Subject: Re: Basic questions regarding pawn hash

Author: Andrew Williams

Date: 00:04:19 06/14/04

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On June 13, 2004 at 14:57:54, Aivaras Juzvikas wrote:

>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)
>

PM is normally over 95% for pawn hash table hits. I did it this way because it
seems more "natural", given some of the requirements of my evaluation function.

Andrew



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