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Subject: Re: Diep as a strong sparring opponent (longish)?

Author: Russell Reagan

Date: 13:04:54 10/13/03

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On October 13, 2003 at 14:26:23, Anthony Cozzie wrote:

>I think it is definitely possible to tune a program for longer time controls:
>fewer extensions and a larger eval.   OTOH, I don't think we're talking hundreds
>of elo points.  Maybe 50. (relative performace at short and long time controls)

As the time control approaches infinity, the strength difference between two
engines becomes zero, because both engines would solve the game and play
perfectly (theoretically, of course). I think this is why people claim that
their engine plays better at longer time controls. The weaknesses in the weaker
engine simply masked.

I believe that you can find out which engine is better by playing many short
games as opposed to fewer longer games. As you get into very short games (1/0),
the relative importance of various strengths and weaknesses becomes skewed. For
instance, poor time management can be fatal in 1/0 games, while it will only
have a slight affect on the results of games at longer time controls.

Different time controls can help you find bugs or weaknesses of different
magnitude. For instance, in a 1/0 game, if you have a big weakness, it will be
exposed by an engine that is more solid all around. That weakness could be time
management or king safety or whatever. The weaker engine will not see what is
coming in the shallower depth allowed in a 1/0 game, while the stronger engine
will pick up on that weakness sooner.

This is simple to see if you play 1/0 games between two engines. I played
Ruffian vs. Crafty in a 1/0 match, and in the majority of games, Ruffian's score
would jump up, and Crafty's score would do the same within 2-4 moves usually.
That would make it pretty easy to pinpoint exactly where a potential weakness
existed in Crafty, or any engine that was tested in this manner.

I think that you need to test at several time controls however. 1/0 games will
show you weaknesses, but the matches also seem to be pretty one sided in favor
of the superior engine. This could make testing whether or not a change is
indeed an improvement difficult. For instance, you might fix your poor time
management and king safety, but your engine might still get the pulp beat out of
it because of some other weakness. 1/0 games pretty much expose any weakness
that exists, from my experience. So to test one change, longer games (longer
than 1/0) could prove more useful. Different time controls will show you
different things. However, really long time controls show you less and less as
the time controls get longer, so there is some point at which there is no point
in playing longer games.

But anyway, I agree with Christophe that being better at longer time controls
isn't exactly a good thing. It only means that the longer time controls hide the
weaknesses of the engine, which does nothing to help you improve your engine,
and if anything it probably hinders your ability to do so.

Also note that this is really only applicable in regard to computer vs. computer
games. Computer vs. human at long time controls is pretty interesting IMO.
Especially correspondance time controls.



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