[computer-go] Floating komi

[Hideki Kato]

I'd like to give here an example to make things clear.

The conditions are:
1) Using digitizing scheme that maps real score to [0,1] (or [-1,1]) 
so that the program cannot distinguish losing/winning by 0.5 or 10.5 
pt at all.
2) Playouts include some foolish moves (usually with low 
but not zero probability), not to connect large groups in atari 
position for example, due to hold its randomness.
3) The position is at early endgame where there are no moves that 
gain greater than 2 pt, for example, in perfect play.
4) Black is behind by 0.5 pt.

The playouts may return winning but gambling move (perhaps with low 
probability) under above conditions, especialy in case of the number 
of playouts is small which is usually true on 19x19, and UCT will 
choose it.

The question is, which is better to keep 0.5 pt behind or to play 
gambling moves (here I mean such moves that B will lose many pts if W 
will answer correctly) with expecting W's (stupid) mistakes?


In addition to above, there is one more issue to consider. If the 
playout has a systematic error, nakade for example, it's not good to 
keep 0.5 pt ahead.  Having more margin is clearly better.

The idea of floating komi helps above two.  I'd like to emphasize that 
I know it's not a universal solution.  As it seems, however, very hard 
to solve nakade problem, it could be a pracitical solution.

-Hideki
--
gg at nue.ci.i.u-tokyo.ac.jp (Kato)