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Subject: Re: Interesting mate test for hashing

Author: Robert Hyatt

Date: 10:07:02 09/10/99

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On September 10, 1999 at 12:58:13, Bruce Moreland wrote:

>Store all mate scores as bounds and see what happens.  I'll tell you what will
>happen.  You'll find this in a few seconds and there won't be any bugs.
>
>bruce


It didn't help a bit, unless I modified the bounds as I mentioned.  I was always
updating a true mate score, and getting rid of this didn't help a bit, as I
expected when playing around yesterday.  The problem was those "mate in N"
bounds that get stored... they can be wrong if they aren't adjusted.  I now
store true mate scores as always, but mate bounds are reduced to just say
"< -MATE+300 or > MATE-300.  I use 300 because of the large tablebase mate
scores that get stored.  But I am still storing actual mate scores as I have
never had a problem with that (i adjust them to mate-in-N from the current
ply of course.)

But those bound mates were causing this particular problem to blow up, because
I would store > MATE-10 (mate in 5) at position X, ply 8, then look that up at
ply=10 or 12 and make a wrong decision.  It was _very_ hard to find in a tree
of 1M nodes...




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