Re: RE: computer-go: Bad Tactical move in MFG

[Jeffrey Rainy <JRainy@xxxxxxxxxxxx>]

>Ok, I'm gonna ask the dumb question: Why does X live after a and c?
>I could probably see it on a 9x9 board as it extends on the right toward the
>corner (assumed empty) and make another eye there, but otherwise?
>

After a and c
We get :

|......
|.OOO..
|OXXO..
|.XO...
|XXOf..
|OXXOOX
|O.XXde
 ------

If O doesn't play 'd', X plays 'd', connects to the new stone, because O won't be able to cut at 'e'.  Then, X can double-atari the two white 
groups. If O took time to prevent this, X has free space to the right to make a second eye.
If O plays 'd', X plays 'f' and then is able to capture one of the two white groups, making a second eye.

The best I see for O after a and c is :

|......
|.OOO..
|OXXO..
|.XO...
|XXO.OO
|OXXOOX
|O.XXX.
 ------

With X to play. This is bad.  O was better enclosing X than letting it get out like that.  

I'm quite surprised that MFGO spotted that sequence and made the right move (good work David).  I'm usually able to beat it, and unless 
another poster had mention this tesuji, I would not have spotted it. 

Jeff.