[gnugo-devel] Semeai

[Inge Wallin]

I just watched gnugo lose a game against TanGo4746.  At move 179, the
following position came up. Gnu go was white and at the move:

   A B C D E F G H J K L M N O P Q R S T
19 . . . . . . . . . . . . . . . . . . . 19
18 . . . . O X O O . . . . X O O O O O . 18
17 . X O O X X X O . . O O X O X X O X . 17
16 . . X X X X O . . O X X X O X X X X . 16
15 . . . . . . O . . O O O X X X . X . . 15
14 . . X . . . . . . . X . X O O X X O . 14
13 . . X O . . . O O . . X . D O O O O . 13
12 . . O . . . . X O . . . O . O X X X . 12
11 . . . O . . . . . O O . O O O X . . . 11
10 . . . + X . . X X X O O X X . X . . . 10
 9 . . O . . . X O O O X O X . X . . . . 9
 8 . . . . X X O O . X X X O X . . . . . 8
 7 . . O O X . X X X X O O O X . . . . . 7
 6 . . O X s X . . X O O X X O X X . . . 6
 5 . . X X . X X X O O X X O O . . . . . 5
 4 . . . X . X O O . O . O . O . X . . . 4
 3 . . . . X O X . O X X X O O X . . . . 3
 2 . . . X O O O X O X . O O X X . . . . 2
 1 . . . X O . . X X O O . X . . . . . . 1
   A B C D E F G H J K L M N O P Q R S T

Consider the two dragons at N18 and O18.  They are in a game-deciding
semeai.  The natural move would be white T18 which makes white alive
and at the same time kills black.

However, Gnu go played M14!  Why?

Here is what Gnu go thinks about the matter:

N18 : B dragon size 20 (24.00), genus 1112, escape factor 0, crude
status dead, status critical, moyo size 0, moyo territory value 0.00,
safety critical, weakness pre owl 0.82, weakness 1.00, owl status dead
... semeai defense move at T18
... semeai attack move at M14
... neighbors O14 O18 L14 O13

O18 : W dragon size 8 (11.50), genus 1122, escape factor 0, crude
status critical, status critical, moyo size 0, moyo territory value
0.00, safety critical, weakness pre owl 0.58, weakness 1.00, owl
status critical
... owl attackable at T18, code 5
... owl defendable at T18, code 5
... semeai defense move at M14
... semeai attack move at T18
... neighbors N18

Notice that the owl defence is at T18 (correct) but the semeai defense
is at M14 (wrong)!  I let Gnu go do detailed trace using -t -t , and
the analysis never even tried T18 as a semeai defense move.

Now, my question is: wouldn't it be natural to try the owl defense
move as the semeai defense move first in any semeai?  Or have I missed
something? 

        -Inge