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Subject: Re: Are over-optimistically evaluations stronger than realistic evaluati

Author: Amir Ban

Date: 12:17:32 04/29/03

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On April 28, 2003 at 11:30:08, Charles Worthington wrote:

>That's an interesting question but I have one of my own. Is not the engine's
>choice of continuations based soley on its eval of the line? Many times I have
>seen Shredder follow its over optimistic evals to a dead draw as white. I would
>rather my program know where it really stands and whether or not it has
>realistic winning chances. Also...I personally would like to know where it
>stands as well. There is nothing quite so frustrating as to have an over
>optimistic eval turn on you and bite you. I have seen numerous situations where
>The King has an eval of +2 against Deep Fritz's -1 and it RARELY works out in
>The Kings favor. It's hard for me to muster faith in an engine that is clueless
>about it's own position and it is the one thing that keeps me from giving
>Shredder a fair shot at becoming my main engine. Enough times of seeing Fritz
>pull the rug out from under my Shredder eval has spooked me I guess. I just do
>not see how it is possible to handle a position properly when you cannot even
>eval it properly and in fast blitz time controls (3+2), I might also add that
>the "optimistic" engines almost always perform more poorly than the well
>balanced engines. The truth seems to perform better than the lie in this case.
>Of course this discussion is about self-inflicted optimism by tampering with the
>parameters so it seems even more extreme. You are taking an already-optimistic
>engine and furthering it's optimism. It would likely take many thousands of
>games to come to a conclusion as to which works best. Honestly though, I think
>that in this case having your program lie to you (and itself) will not prove
>beneficial. The program will play better if it has a full understanding of its
>actual chances and not imagined ones...Optimism causes the program to
>overestimate it's chances and play far too aggressively (ie. unwarranted
>sacrifices) in certain positions where caution is warranted. Against a human
>this may prove beneficial but against a program firmly grounded in reality it
>may prove fatal. So, like in life, I think the truth has to be better than the
>lie. And I think that extensive testing of these settings would show that, more
>often than not, the lie would come back to bite you.
>

I agree.

I believe overvaluation is the most common reason for engine losses. It's much
more common than undervaluation, a less fatal problem. This is especially true
in tactical situations, where the program with overvaluation seems not to see
tactics, because its search is meaningless.

Amir




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