Hi!
On Thu, Feb 11, 2010 at 10:32:49AM +0100, Le Hir Matthieu wrote:
> First, I'm wondering how komi is determined when a dynamic system is used :
>
> * According to this page : http://senseis.xmp.net/?Komi%2FvalueOfFirstMove
> the value of komi at first move is half the points the black move is
> supposed to be ( 14 points) > 7,5 komi in even games.
> How does this apply to high handicap games ?
I *think* that komi value is miai-counted, not deiri-counted, so in miai
counting that corresponds to the 7.5 value also proposed in the article.
I have never been an expert in the counting theory, however, so maybe
I am wrong.
Pachi uses 7.5 points per handicap stone, in some testing I also used 8
points per stone which gives similar winrates. It makes no theoretical
sense to use the 0.5 fraction in this, but it seems to work well enough
and I did not have time to tune for better value.
> From what I think I understood, dynamic komi is supposed to try to keep the
> game more even.
> If the computer is black, playing at 9 handi, will the " burden komi" (
> negative) be 9 x - 7,5 ? - 67,5 ? It sounds highly improbable.
Yes, this is the komi value pachi uses. I have found that higher komi
values work similarly well (perhaps a bit worse) as long as the komi is
not completely ridiculous.
> On the other hand, 9 handicaps are supposedly giving an advantage of 90 to
> 120 points, so my natural thought would be that the bot would give itself at
> least a negative komi of that many points ?
>
> I can't figure out well how komi is determined at first move.
extra_komi = 7.5 * handicap_stones_count
Then it is linearly decreased until it hits 0 at move 200.
This is the most naive implementation. In practice, neither extra_komi
determination nor its application throughout the game should be linear,
probably. There is a lot of experiments to be done. :-)
> In relation with the previous question, I'm wondering how komi is determined
> and what its value is for every handicap game ( as black and as white). Is
> there a specific value for each ( before first move is played) or is it only
> determined by the way it was programmed and the programmer's preferences ?
It is only determined by the programmer's preferences and more
importantly empirical measurements of what kind of values worked best.
P.S.: For some measured dynamic komi positive effects, please see the
presentation I posted few months ago. I plan to finish up and submit a
paper with investigation of also other approaches hopefully in time for
the IEEE call for papers. ;-)
--
Petr "Pasky" Baudis
A great many people think they are thinking when they are merely
rearranging their prejudices. -- William James
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