Re: [gnugo-devel] Bug: gnugo plays inside own territory for no reason

[Gunnar Farnebäck]

[Sorry for the duplicate, forgot to add Malcolm the first time.]

Malcolm wrote:
> For the attached sgf file, gnugo thinks that white should play N5:

This is the position:

   A B C D E F G H J K L M N
13 . . O X X X X O O O O . . 13
12 . . O O X O O O X O O O X 12
11 . O . O X X O X X X O O . 11
10 . . O X . X X X . X O . O 10
 9 . . O X X X O . . . X O O 9
 8 . O . O X O X X . . X X X 8
 7 O O . O O O X . X + X X O 7
 6 X X O O O O O X . O X O O 6
 5 X X O . X X O X X O X O . 5     WHITE (O) has captured 5 stones
 4 X O O X X O O O O X X O X 4     BLACK (X) has captured 4 stones
 3 X X X X . X O X X O O O O 3
 2 . . O O X . X . X X O . X 2
 1 . . . . X X X X X O O X . 1
   A B C D E F G H J K L M N

and according to the sgf file the game was played with Japanese rules.

> address@hidden:~$ gnugo --score finish -l Defner-pepsiman-20041213.sgf
> 136 white (O) move N5
> 137 black (X) move D5
> 138 white (O) move : PASS!
> 139 black (X) move : PASS!
> Black wins by 7.5 points
> 
> This gives black an extra point, so I think it has made a mistake.

No, N5 is correct. The lower right corner is a seki and under Japanese
rules no points are awarded in seki for either player. Thus there is
no territory at any of the points, N5, N4, M2, N2, M1, or N1. In fact
white gains one point by playing N5. It's still a seki after the move
so there is no territory but the captured stone at N4 now counts one
point as a prisoner.

Under Chinese rules white should play D5 before N5. (I don't know if
N5 is necessary in that case but it certainly doesn't hurt white.) 

/Gunnar