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Subject: Re: Endgame blunder

Author: Ulrich Tuerke

Date: 06:35:48 03/05/98

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On March 05, 1998 at 05:39:03, Kai Lübke wrote:


>Now Fritz took a 2 minute search (approx.) going to 14 or 15 ply IIRC,
>yet returned a draw score for Rc2.
>Rebel instantly said +4,30 for Rxc2 then.
>
>*Then*, surprisingly, Fritz needed only a few seconds to report a -4
>score itself! Really strange why it didn't see it before, that one extra
>ply can't be the only reason.
>
>But I've seen similar (though not quite as drastic) things time and
>again, that one program made a deep search, returned an even score,
>predicted its opponent's move correctly and then suddenly dropped to -3
>in seconds...
>

This behavior is quite typical for a "pre-processing" program, i.e. a
program performing large (time consuming) parts of the evaluation at the
root nodes only. Even a very deep search does not have the chance to
change the results of the pre-processor's evaluation, but will only
slightly correct these root evaluations.
But when it comes to the next move, a new run of the pre-processor will
correct the evaluation. Seems to me, that something like this happened.

Regards, Uli



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