Hi Don!
I just started an experiment! First some thought about what I believe is
the factors involved. And then I describe the setup and some preliminary
impressions and results.
Quoting Don Dailey <[email protected]>:
1. boardsize could be a factor.
I would not expect it to be useful on 9x9, especially dynamic komi would
get incredibly unstable on small board towards the end of the game. So what
I am testing is 19x19.
2. it may be more feasible in handicap games.
My previous experiments for even game showed little or no gain. My
subjective feeling is that it is in high handicap games on 19x19 where
effect can be strong.
3. it may work better against humans for psychological reasons.
I cannot measure that.
4. Maybe I did not stumble on the right approach when I did my
experiments.
With dynamic komi the MC evaluation suffers more from noise because when
the win rates get close to 100% it even makes MC programs play randomly (or
systematically from the top left corner or something similar). This problem
becomes greater the stronger the program is. It is probably not so bad
because a stronger program will also have larger difference in win
rates for
strong and weak moves. This is my explanation why Valkyria probably only
benefits from.
The other reason why dynamic komi may be good is that a MCTS program
prefers high win rates over a safe winning margin leading to the 0.5 points
syndrome. On 9x9 boards present programs do not appear to suffer from this.
They are so strong that with a "safe" 0.5 lead they win without mistakes.
And if they do suffer from it still it is not clearly visible. It
looks like
a middle game mistake and then they realize they are behind a wild fight
occur.
On 19x19 this is probably a major problem for most program without dynamic
komi or some other greedy search method. If a game is long and the score
drops to 0.5 long before the game is finished the program must
play the rest
of the game as strongly as the opponent. This is a disaster for black in
high handicap games. In the worst case even an opponent just slightly
stronger can win with a large handicap, because the game become even too
soon.
Ok, enough babbling about the stuff dynamic komi could possible fix.
I just started an experiment to make Don happy. It is not so easy to make
such an experiment completely satisfactorily but it will be a first step to
test Valkyria at least.
I want to show that Valkyria plays stronger as black with 9 handicap
stones on 19x19. The problem is that I would need an extremely strong
opponent to beat Valkyria as white under normal time constraint. And I have
no access to such an opponent.
So I let Valkyria play Black with about 1s per move and White with 10s per
move approximately (1000 and 10000 playouts respectively).
I run two conditions in parallel one where black use dynamic komi and one
where it play without it. My hope is that the modest difference in playing
strength will be enough to make a difference. In the worst case black wins
100% of the games in both conditions.
The good news is that I think the effect of dynamic komi in this
particular experiment is huge just from watching the very first games.
With dynamic Komi black is really aggressive. It is tactically weak but
fights in a way that the white groups are eyeless and have no territory. It
kills large white groups in almost every game.
Without dynamic komi white is allowed to establish relatively strong
groups all over the board without a fight and gets closer to an even game
for almost every move played. So far white won 5 out 7 games which
I did not
expect. 10k vs 1k should not be more than a 3-4 stones I thought.
White has won 1 game out of 6 against black with dynamic komi.
It is too early to make any conclusions yet but if the effect is as large
at it seems to be I can probably give some convincing numbers already
tomorrow.
Caution is important also. As in all self play experiments effect tend to
be exaggerated. The next step is this seems to be a good setup is to test
against Fuego. I would also like to scale it up using 10k playouts
for black
and 100k playouts for white to if effect stays with better play for both
colors.
It may also be that the effect is double. White with h9 has winrates below
20% in these games and play desperate move rather than patient moves quite
often. Maybe white can use dynamic komi too to some degree? Or perhaps a
linear komi to make it play the opening more sound and then get more
desperate later?
-Magnus
_______________________________________________
Computer-go mailing list
[email protected]
http://dvandva.org/cgi-bin/mailman/listinfo/computer-go
