[computer-go] Interesting tactics statistic

[Mark Boon]

A while ago there was a discussion about storing results of tactical  
searches. Since I'm just starting to touch the tactical search area  
in my new project I decided to review the situation.

So as a start I decided to gather some simple statistics (based on  
this 40,000 game collection discussed before). First of all there are  
about 8.5 million moves in this collection, making an average of 210  
per game. So far I had always assumed this to be in the 225-250 move  
range. But probably the number of games that get resigned reduces the  
number somewhat.

Next I counted the number of tactical 2-liberty searches there are in  
an average position. For this I needed to know how many chains are in  
atari on average, and how many chains have 2 liberties. The  
respective numebrs turn out to be 2.3 and 7.7, making it a nice round  
10 per move. Somehow I had thought these number would have been  
larger....

Next I'll have to see whether it's faster to simply read those 10, or  
if time can be gained by a clever algorithm that only reads those  
that are affected by the last move. I'll post those results too when  
I get to it.

	Mark Boon