Rybka Chess Community Forum
What is the significance of "contempt" in Rybka's parameters?
What should it be set as?
In Rybka 2.3.2a, it only affects immediate draw decisions, like whether to repeat position or allow fifty move rule draw. In Rybka 3, it is very important. It affects many aspects of play, such as whether to seek or avoid even trades, whether to open or close the position, whether to seek or avoid pawn symmetry, etc. Default setting for play (in analysis mode default is zero) is 15, as I concluded this was best against our leading engine rivals, and it also makes the play more interesting in general. Against another Rybka 3 on equal hardware zero is best of course; you should not have contempt for yourself! Against human players a much larger value is appropriate, and we even let Rybka calculate the proper setting if you input your rating!
> Against human players a much larger value is appropriate, and we even let Rybka calculate the proper setting if you input your rating!
How do I get Rybka to calculate the contempt setting for a particular elo opponent?
I'll have to check which GUIs if any support this feature, and whether it actually was implemented as planned.
It seems Contempt also adds to the eval, e.g. when I set it to 100 it evaluates an equal position as +1 pawn. I don't like this feature, because you have to know the Contempt setting to correctly read Rybkas evaluation.
Indeed, we debated this internally, as it's a(nother) change in computer chess convention. In the end we decided that it was more logical, and also a reminder about the contempt which is in use.
If you don't tinker with the defaults, just remember that in game play (not analysis) the contempt is always 15. This means that in the opening Rybka's eval is optimistic by nearly 15 centipawns but that this figure drops as the pieces come off.
LK, in correspondence analysis, what should be the setting for both contempt values?
(I don't understand the difference between the two types of contempt value since analysis is just another form of play.)
If you use infinite analysis or fixed-depth, only "contempt analyze" matters, and the default is zero, as that will give you objective analysis. A positive value for contempt is used when you believe that your engine is stronger than your opponent. For actual play, the default is 15 because Rybka 3 is stronger than all possible opponents except another Rybka 3. For analysis, you would set a positive value if you know that your opponent (or his computer) are inferior to you and your computer or if you must avoid a draw for tournament reasons; otherwise use zero.
Thank you for an enlightening and useful definition of "contempt."
> A positive value for contempt is used when you believe that your engine is stronger than your opponent.
Am I right in thinking that this is true if computer is white. But if computer is black,and we think engine is stronger than opponent then we have to set comtempt Analysis to a negative value, and this applies only to analysis not play?
I forgot that we made "contempt analyze" from White's point of view, so this should be right.
>For analysis, you would set a positive value if you know that your opponent (or his computer) are inferior to you and your computer or if you must avoid a draw for tournament reasons; otherwise use zero.
Actually, Contempt Analysis is always from white's point of view. :)
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