Re: [gnugo-devel] life & death (3.3.5)

[Arend Bayer]

On Sun, 25 Aug 2002, Paul Pogonyshev wrote:

> in the position below black is to play, state of the white group is
> ko. since there're no threats, it is alive.
>
> if gnu go plays black, it setups the ko and, of course, loses it:
>   a8 - a7
>   c8 - a9
>   e3 - a8

This is acceptable. If GNU Go can attack with ko, it doesn't check
whether it has sufficiently many ko threats available on the board. I
doubt many players below 4d would usually do this (in other words, I
usually don't, and I am 3d...)

> i tried to play black and started an attack that can be answered:
>   a7 - a8
>   a6 - e3 ???   this mistake killed the entire white group
>   a5 - f3
>   g3 - pass
>
> the strangest thing is that gnu go thinks that white group is still
> alive and that black stones inside are dead. even if all white stones
> was connected, it would be seki!

This is indeed bad, and we should add the position after a7-a8-a6 to our
regression tests. The eye space analysis is going wrong here.

Thanks
Arend