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Subject: Re: Ultra small pawn hash efficiency

Author: Robert Hyatt

Date: 16:59:38 11/21/02

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On November 21, 2002 at 17:58:43, Ingo Lindam wrote:

>On November 21, 2002 at 15:39:27, Robert Hyatt wrote:
>
>>On November 21, 2002 at 12:39:24, Matthias Gemuh wrote:
>
>>>Some hasty and wrong thinking then, when I implemented my pawn hash.
>>>Maybe I somehow excluded strange positions like all pawns on 2nd and 3rd rows.
>>>I shall check my code and logic later.
>>>I generate keys such that they lie in range 1..2x64kB and use them as index.
>>>I hit 95%..99% in middle game and WAC.
>
>>Just one white pawn gives you 48 different positions.
>>one white pawn and one black
>>pawn gives you 48*48 different positions.  or, rounding down a bit, 48 could be
>>replaced by 2^5 (32).  48*48 could be approximated by 2^10 or 1024.  two more
>>pawns and we are going to blow past 64K positions.
>
>I don't see a contradiction between the two statements. Aside from there are
>just 48*47 possible positions with one white and one black pawn you count a lot
>of positions having nothing todo with chess reallity and even more positions
>being atleast very unlikely. I can imagine that there are not more than 2x64k
>positions covering 95% of the occuring midgame positions.
>
>[D] 8/1ppppppp/7p/8/8/P7/PPPPPPP1/8 w - -
>
>internette Gruesse,
>Ingo

For the one pawn vs one pawn case, I'd bet that I could find one example of each
possible
position quite easily in a large game collection.  Those positions are not that
oddball, IMHO...

Add 2 more pawns and we are beyond 64 K _possible_ positions...  Of course all
are not
likely in the same search from the same root position...  But big trees should
blow 64K out
quickly.  I'll try it later since I can do that easily...





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