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
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