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Subject: Re: Shredder wins in Graz after controversy

Author: Gerd Isenberg

Date: 15:35:23 12/09/03

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On December 09, 2003 at 12:15:59, Andreas Herrmann wrote:

>On December 09, 2003 at 11:29:58, Sune Fischer wrote:
>
>>On December 09, 2003 at 11:13:56, martin fierz wrote:
>>
>>>On December 09, 2003 at 10:50:23, Sune Fischer wrote:
>>>
>>>[snip]
>>>
>>>>If the bare engine had been playing he would have had to add a few things the
>>>>GUI normally takes care of.
>>>>For UCI engines it is expected that the GUI handles certain (trivial) things.
>>>
>>>claiming a draw on 3-fold repetition is *not* a trivial thing. there are
>>>different possible cases:
>>>
>>>1) if your opponent avoids it, he loses
>>>2) if your opponent avoids it, he wins
>>>
>>>in case 2) you should of course claim the draw, because perhaps he will notice
>>>he could avoid it. in case 1) however, you can safely repeat the moves, and not
>>>claim the draw. it is *not* mandatory to claim a draw on the 3rd repetition. so
>>>you should basically not claim it if you might win if your opponent avoids the
>>>draw.
>>
>>Are you suggesting the UCI protocol should be forbidden? :)
>>
>>>how do you expect a GUI to make the right decision? imagine the following
>>>absurdity: jonny is running without GUI and happily repeats moves against
>>>shredder, and does not claim the draw because the engine doesn't know about it.
>>
>>So you're saying if we take an engine and subject it to something it wasn't
>>designed for it wouldn't work right?
>>Doh!
>>
>>As it were, the engine was *not* designed to play in the console or in winboard.
>>The whole point of UCI is that certain things are easier, e.g. no messy detect
>>repetition draw as in winboard or the console.
>>The engine only has to do it internally, and Jonny clearly was doing that.
>>
>>>shredder has a bug and allows a 3-fold repetition but will deviate before the
>>>fourth repetition. now shredders GUI stops shredder from moving, and says "i
>>>claim a draw with my move XY because of 3fold repetition" - this would have been
>>>hilarious for everybody except SMK :-)
>>
>>Not really.
>>The engine always plays the best moves it can find, if that is a repetition then
>>it's a repetition. No point in continuing because the engines sees the draw and
>>wants it.
>>
>
>I wonder a bit, why Shredder doesn't repeat the moves after the third
>repetition.

Because there was a move with a score > 0 ;-)

Taking the draw if 3-fold repetition at the root is an option according to FIDE
rule 92b) (or was it 72?), even without playing a move to force a further
repetition. So you may ignore the draw score at the root and search further on,
looking for a deviation. If you find nothing better than e.g. 0.0 after a while,
you may still claim the draw and finish the game.

>Was Shredder restarted after the bug was seen by the operators or
>was the contempt factor changed after it? If yes, the question is also: Is this
>allowed inside the ICGA rules?
>

No, changing contempt factor is not allowed during the game, of course.

But why did Shredder allow to repeat positions at all with such positive score?
Doing a few fast moves for time control reasons to pleasurably find the best
winning way with some more time? Or to test or confuse the opponent, who is
probably happy with draw scores?

One possible explanation may be that Shredder assigned draw scores only after a
3-fold, at least if the first repetition occured outside the current search.
Maybe due to some temporary "no progress", Shredder tended to delay some maximum
to the leaves?

My guess is that Shredder simply had a bug in handling the FIDE rule 92a)
correctly, that the opponent may already claim the draw before the 3-fold
repetition occures.

Gerd

>
>
>>If you don't want the engine to go for a repetition you can adjust the contempt
>>factor.
>>
>>In case of bugs anything can happen of course, and in this case Jonny got lucky,
>>it happens.
>>
>>>since 3fold repetition is something you claim or don't claim based on the
>>>current position, it is clearly something the GUI shouldn't be doing!
>>
>>Perhaps, but then the ICGA should have banned UCI engines long before the
>>tournament started, they didn't hence they accepted such behavior, period.
>>
>>-S.
>>>cheers
>>>  martin



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