[gnugo-devel] some kind of bug, bad position reading - v3.2

[Paul Pogonyshev]

Problem 3 from igs (http://igs.joyjoy.net/English/tsumego/3.html)

|XXX.....
|.OOXXX..
|...O....
|.O......
+---------

I attached an sgf file with this position (board is filled with black
stones to make gnu go concentrate on the position).

A bug:
   enter these commands:
      load igs3.sgf
      listdragons (or showdragons)
      a2          (or d1)
   Gnu go fails due to some kind of memory corruption. Parts of *owl
   structure are unaccessible in do_owl_attack (engine/owl.c). This
   causes access violation in pop_owl function called from line 1582:
         pop_owl(&owl);
   Note that listdragons/showdragons are needed to reproduce the bug.
   In case it is a platform-dependent bug, i'm using windows 98.

Furthermore, gnu go fails to attack white stones:
B: e2
W: d1         |XXX.....
B: a3         |XOOXXX..
W: a2         |O.OOX...
B: e1         |.O.OX...
W: c2         +---------

If gnu go plays white:
B: a2         |XXX.....
W: a3         |OOOXXX..
B: d1         |X..O....
W: pass       |.O.X....
              +---------

So, it "understands" that white stones are dead after two moves, but
cannot find that moves if attacking.

And yet another thing. If gnu go is to make a move for white in
position

|XXX.....
|XOOXXX..
|O..OX...
|.O.OX...
+---------

it moves b2. I think that c2 is a better move since b2 leaves a
ko-threat for black (in case of a ko) at c2.

regards,
  Paul Pogonyshev

Igs3.sgf
Description: Binary data