[computer-go] Greedy search vs UCT

[Magnus Persson]

I have checked if there is a difference for Valkyria in using  
confidence bounds or just greedily search the move with the highest  
winrate. This is Valkyria 3.2.0 using 512 simulations per move against  
GnuGo 3.7.10.

UCT_K	Winrate	SERR
0	58.8	2.2 (greedy)
0.01	56.8	2.2
0.1	60.9	2.2
0.5	54.2	2.2
1	50.6	2.2

As you can see up to uct_k = 0.1, the winrate aginst gnugo is more or  
less constant (500 games was played for each value of uct_k) and then  
it declines.

So although 0.1 was best I cannot claim that it is better than a plain  
greedy search.

I will repeat this using 4 times as many simulations per move. The  
search  sensitivity to uct_k may depend on how deep the tree is  
searched.

-Magnus