[computer-go] The effect of the UCT-constant on Valkyria

[Magnus Persson]

I have already posted the following results. The results shows the  
winrates of Valkyria 3.2.0 against gnugo at default strength.


512 Simulations	per move
UCT_K	Winrate	SERR
0	58.8	2.1 (Winrate only)
0.01	56.8	2.2
0.1	60.9	2.2
0.5	54.2	2.2
1	50.6	2.2

With 512 simulations there is not much work done in the tree. So I  
extend the test to 2048 simulations and also added the parameter value  
2 to see what happens when search get really wide.

2048 Simulations per move
UCT_K	Winrate	SERR
0	80.7	2.3 (Winrate only)
0.01	83.3	2.2
0.1	83.7	2.1
0.5	77.3	2.4
1	71.3	3
2	62	4.9

The number of games are 300 for parameters 0 to 0.5 and a little less  
for parameter values 1 and 2

The results confirm that Valkyria still benefits from using confidence  
bounds with UCT, although the effect is really small.

Also the effect of the constant might be a little greater with 2048  
simulations rather than for 512. Still the curves look more or less  
the same. Does anyone have experience doing a test with different  
amounts of simulations where the best parameter value depend on the  
number of simulations?

I prefer to use a low amount of simulations since it is simply faster,  
and also if the winrate of Valkyria gets to close to 100% it becomes  
harder to measure the effect of different parameter settings. Maybe I  
should quit testing against gnugo, and try something stronger.

-Magnus