Interesting! I got confused by GoUctUtil::IsMutualAtari, but now I'm
not
sure if it is even really used, nor exactly what is it supposed to
actually test in that condition. :-)
Then it turns out that I'm already implementing pretty much all the
tests in Pachi as Fuego is, just probably way too mistuned and buggy,
ah well... ;-) The strange thing is, I don't seem to be getting any
noticeable gain from 2-liberty tactics and checking the pattern at two
last moves instead of just the last one; did you get a big gain from
these?
The aim of mutual atari checking is to keep seki from being destroyed,
by avoiding moves that are both selfatari and atari on the opponent.
There are some size limits on the blocks involved, for example you
need to be able to almost-fill a nakade space by selfatari-ing your
nakade block.
I had programmed this a long time ago, but while it was working
beautifully on the seki regression test cases, it lead to a small
overall decrease in playing strength. It has only become profitable
(and enabled) shortly before the match against Chou 9p. The reason it
works now in Fuego is that it is used in conjunction with a
"balancer", which means that Black and White must use this rule
roughly equally often. I think we measured about 52% win rate in self-
play from using mutual atari avoidance plus balancer.
The original version of 2nd-last move pattern improved winning
percentage against GnuGu from 73% to 78% with 3k simulations. That was
in November 2007.
2-lib tactics was about 2% improvement around the same time but has
been improved since.
If I ever write a full paper on Fuego, I will test the effect of
leaving out each of the existing rules individually. Or even better,
someone else will do that :)
Martin_______________________________________________
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