[computer-go] Suicide question

[Jacques Basaldúa]

Michael Wing wrote:

> In my program (which implements undo), the cost of
> for suicide detection is around 1%, which means it
> would lose 1.5 ELO points.

In programs that somehow maintain lists of legal moves
or even probability distribution functions over the legal 
moves, avoiding suicide is free. I fact, adding the 
suicide move to the list would cost.

> On the other hand detecting superko costs more like
> 6% or so, which costs 9 or more ELO. So a benefit
> of 1 ELO for doing superko right may not be worth
> the cost.

I guess you mean a bullet proof test from the beginning
of the game. I only test the last 7 moves (if enabled, 
it can also be disabled) and that does not cost much.

The reasons why I use 7 moves are 2:

* I have never found among strong players a need for
repetition other that triple ko and double ko on a 
group with no eyes. (Both are 6 moves long.) My point
is: If the program is so weak that it does silly 
repetitions, improve something else. If it is so strong
that it has the same problems as strong humans, detect
superko.

* My hash system can use only half of the hash (32 bits)
and detect the collision with probability 1. (Because of
the properties of the keys, you need at least 8 keys 
for a combination of keys giving zero.)

A reason I can figure for ignoring repetition in the 
playouts is: If the playouts are random, it won't happen 
much anyway. The probability of a repetition of 6 random 
moves is too small to care about. But in real play it is
frequently a fight for the game. The player forced to
avoid the repetition will resign if it is about the 
life of a big group.


Jacques.