[Computer-go] useless ko threats

[Stefan Kaitschick]

Bots love to throw in useless ko threat type moves now and then.
Sometimes its just a wasted threat, at other times it loses a useful
liberty too.
Why do even strong bots show this "stupid" behaviour?

Ko threat type moves have one thing in common: a big payoff if the opponent
answers incorrectly.
If the first response tested is wrong, then the ko threat will start off
with a very good winrate.
The correct response will be found fairly soon, but by then the original
move will have a winrate bonus.
This bonus is small, but it is there.
The problem is, that the winrate degradation, that a useless ko threat
causes, can also be small.
So if the (erroneous) bonus outweighs the (real) loss, the bot will
conclude that throwing in the ko threat is good.
To remedy this, I think the winrates of early replies that prove
ineffective, have to be discounted from the parent node.
I know its not as easy as it sounds, because the winrate also directs the
search.
I'm not proposing a method here, just pointing to the problem.

Stefan
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