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Subject: Re: computer programs cannot see a very simple draw in a pawn ending

Author: Ernst A. Heinz

Date: 03:21:36 06/23/98

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On June 23, 1998 at 03:58:26, Ulrich Tuerke wrote:

>On June 22, 1998 at 16:11:47, John Stanback wrote:
>
>>This is a nice position for testing/debugging transposition
>>tables and draw by 50 move rule.  I modified Zarkov to allow
>>it to search beyond 100 plies, but it didn't find the draw.
>>Then I added 1 line of code to store positions which were
>>scored by the 50 move rule or draw by repetition in the
>>transposition table before returning from search().  Now it
>
>I'm afraid this can imply some problems for the search. Assume
>that you have flagged a position as a "draw" in your transposition
>table because the 50 move rule had applied. If this position is later
>reached at a lower depth via a transposition, then the hash table
>would return a "draw". But may be, it really isn't because at lower
>depth the search might be still below the 50 move threshold ?
>This could result in real foolish moves returned from the t-table.
>IMHO, similar remarks hold for the draw by repetition case.
>
>I think that I had once detected problems through storing these
>kinds of positions in the hash table. Now, I don't store them.
>
>Did I get somehing wrong ?

I do not think you got something wrong -- I completely agree with you.

=Ernst=



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