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Subject: Re: False hash probes in endgame and how to avoid this problem

Author: Robert Hyatt

Date: 07:17:58 02/02/03

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On February 02, 2003 at 03:38:00, Sergei S. Markoff wrote:

>Hello Robert!
>
>>You can fudge around all you want, but there is no way to solve the problem
>>short of storing the complete path played to reach a position in the table
>>entry,  Which would make the table useless and way too small...
>
>Is it proven?

Yes.  The game of chess is a graph, not a tree, which means the pathways are
interlinked in odd ways.  But the 50 move rule and repetition rules are
written with the idea of a tree, because of the tranposition table.  The only
way to fix it is to include the "graph information" which is the complete path
from the starting position to the position being stored...

That's simply not doable.


>
>>You just have to ignore it.
>
>I see Crafty is trying to clear hash table in endgame to avoid this problem...
>What you think about not accepting hash probe in some cases in endgame?
>
>Sincerelly yours,
>Sergei

It clears it as it nears the 50-move barrier, which is about all you can do
to avoid walking into a 50 move draw in a winning position.  It isn't optimal,
but it helps.  Note that it only "helps".  It isn't a total solution at all.

I'm not sure what you would do to "not accept some hash probes."





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