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Subject: Re: Shredder wins in Graz after controversy

Author: martin fierz

Date: 10:50:14 12/09/03

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On December 09, 2003 at 12:32:15, Robert Hyatt wrote:
[snip]

>I don't see how this matters since the engine doesn't understand the concept
>of "my opponent might make a mistake."

and this is exactly where the problem is. i understand it, and you understand
it, but 99% or 100% of all chess engines don't understand it. which doesn't
change matters: if you have a draw "in hand", you don't claim it. you let the
other guy decide whether he claims it or makes a mistake. computers will say the
position is 0.00. it is >= 0.00. of course it is 0.00 if the opponent plays
well. but you don't know that he will play well, so you have him prove it.
even if your engine doesn't understand the concept, your opponent can still make
a mistake :-)

[snip]

>>there are so many positions where both sides are forced to repeat, because they
>>lose if they don't. e.g. i sac something, get a perpetual and if you go on the
>>wrong square with your king i win. if i make a quite move you defend against the
>>perpetual and win. this is a very common situation. i will definitely not claim
>>the 3fold repetition in such a position, because you just *might* go on the
>>wrong square. i can't do anything about it, the game is a draw. but since you
>>can still go wrong i won't claim the draw just yet, i have no reason to. i can
>>always claim it later.
>
>This does not happen in computer vs computer games.  They resolve this at the
>_second_ repetition, they don't have to wait for the third and then play through
>it to fix the problem.

replace "this does not happen" with "this should not happen in c-c games". for
example, you can imagine the situation where it's hard to see that avoiding the
draw is a loss, in fact, it first looks like a win. you're searching that move
which avoids, then you fail low, allot more time, and the next time you search
that position you're in time trouble and play the move which looks like a win
but is a loss. this is possible if you clear your hashtables, for example....
besides, there is always the possibility of a bug. e.g. shredder repeated the
winning position 3 times, instead of 2. according to your theory, "this does not
happen". of course it does, it was a bug. if it happens to SMK, it can happen to
anybody ;-)

cheers
  martin



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