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Subject: Re: Ultra small pawn hash efficiency

Author: Robert Hyatt

Date: 12:39:27 11/21/02

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On November 21, 2002 at 12:39:24, Matthias Gemuh wrote:

>On November 21, 2002 at 11:07:38, Robert Hyatt wrote:
>
>>On November 21, 2002 at 08:26:48, Matthias Gemuh wrote:
>>
>>>On November 21, 2002 at 08:15:50, Georg v. Zimmermann wrote:
>>>
>>>>On November 21, 2002 at 07:13:10, Vladimir Medvedev wrote:
>>>>
>>>>>depth = 9, from initial position:
>>>>>
>>>>>pawn hash = 1 entry -- 28% successful hits
>>>>>2  --  33%
>>>>>3  --  37%
>>>>>4  --  38%
>>>>>5  --  41%
>>>>>7  --  43%
>>>>>10 --  45%
>>>>>100 -- 60%
>>>>>...
>>>>>65K -- 84%
>>>>>
>>>>>I was quite surprised with this :)
>>>>>Even 1-node pawn "hash" helps a lot!
>>>>
>>>>Doesnt one get something around 99% with big tables ?
>>>
>>>
>>>
>>>With 2x65kB. More is not needed, if only pawns are considered.
>>
>>
>>There are more possible pawn positions than that.  White has 8, black has 8.
>>there are
>>48 possible squares any of them can be on...  That is a pretty big number.
>
>
>
>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.
>
>Thanks,
>Matthias.
>
>Thanks,
>Matthias.

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.





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