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Subject: Re: hash tables

Author: Uri Blass

Date: 08:44:54 12/20/03

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On December 20, 2003 at 11:21:26, Kurt Utzinger wrote:

>On December 20, 2003 at 11:03:04, scott farrell wrote:
>
>>On December 20, 2003 at 10:53:56, Jay Hysenbeg wrote:
>>
>>>hi,
>>>i was wondering what happens when u use low hash for a long time control. to the
>>>point where the hash is normaly filled before the eng has made its move.
>>>thank you
>>>jay h.
>>
>>well, things start to deteroriate, your move ordering isnt as good etc., and
>>your branching factor ends up so bad that it cant get from say 10 ply to 11 ply
>>or whatever, it sort of like hits a brick wall somewhere.
>>
>>To what extent this happends largely depends on your replacement scheme, and how
>>well it deals with overwriting entries.
>>
>>I test changes to my hash by running extremely small hashes, like 16k entries,
>>just to see how it will cater.
>>
>>Scott
>
>     Size of hash tables seem to have much less influence
>     than I have imagined. This showed a test over 50 games
>     between Fritz 8 [96 MB hash] against Junior 8 [8 MB hash]
>     and a second 50 games match Fritz 8 [8 MB hash] vs Junior 8
>     [96 MB hash]. The final result was in both matches almost
>     identical [25m+10s].
>     Kurt

It is possible that 8 MB is already almost enough for your time control.

It is possible that 96 MB is only 10 elo better than 8 MB at the time control
that you tested but if you use 12 MB against 1 MB you get bigger
difference of 25 elo.

I do not expect more than 25 elo based on upper bound of 7 elo for doubling the
hash tables.

Even if the difference is 24 elo then it means that you can expect only
26.5-23.5 for the stronger side in 50 games and the statistical error in a match
of 50 games is more than 1.5 point.

Uri



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