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

Author: Ulrich Tuerke

Date: 00:58:26 06/23/98

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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 ?

>gets a score of 0 after a 101 ply search, which takes about
>6.7 seconds.
>
>John
>
>...



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