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Subject: Re: hash tables

Author: Uri Blass

Date: 09:35:56 12/20/03

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On December 20, 2003 at 12:15:41, Thomas Mayer wrote:

>Hi Kurt,
>
>>     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].
>
>when I remember correctly there was a difference between the results and the elo
>difference was very near what I would expect when I take the Théron rule for
>doubling hash size... (I call it Théron rule because he was the first one I saw
>who made the statement that he guess that doubling hash size is around 7 Elo) -
>afaik the difference was even slightly bigger then what we would expect
>according to the above rule... but of course in the given margin of error of
>EloStat...
>
>A more relevant difference is to have hashtables or not to have them, especially
>in endgame - e.g. against engines without any hashtables I have some chances to
>win when I survive until the endgame - against engines WITH hashtables I usually
>have no chance at all...
>
>Greets, Thomas

I think that the main reason is simply the fact that engines with hash tables
are usually stronger not only because of hash tables and have more knowledge
about endgames.

movei cannot play without hashtables but if I release a version without hash you
will probably not have chances against it also in the endgame.

I believe that hash does not help a lot for movei espacially when today I do not
use it for pruning and I will first learn crafty's code about hash.

I believe based on some test positions with one entry for hash tables that today
being 2 times slower is a bigger demage for movei than not having hash(I do not
believe that one entry changes much).

I expect it to be changed when I implement hash correctly.

Uri



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