Running gnugo --quiet -l tune.sgf -L132 --decidedragon H7 -o vars.sgf we learn that the owl code finds that:
H7 can be attacked at H2 (16 variations)
H7 cannot be defended (39 variations)
This produces a variation tree in the SGF file vars.sgf which
you can navigate using CGoban. The tree looks like this, and I've
put the cursor on the most significant node:
This is the position:
The comment in the file at this point states:
defense move at H7 (variation 36, hash 313eb3e1)
owl_defend H7: 0 (genus 0)
This node only has one daughter, so only one move was considered
at this point, and it was not G1. The move considered
was H2 (not shown). Thus we need to add a pattern in
owl_defendpats.db. The following pattern may seem very
specific but since the comb formation is a basic one, there
is no need to over-generalize it.
Pattern D195
# db added (2.7.201)
?OOO? comb formation
O.X.O
O.*.O
-----
:8,-,value(50)
Since the two center points in this formation may be regarded
as miai, we add another pattern:
Pattern D196
# db added (2.7.201)
?OOO? comb formation
O.*.O
O.X.O
-----
:8,-,value(50)
After these patterns are added, GNU Go finds the right move,
as gnugo --quiet -l tune.sgf -L132 --decidedragon H7 -o vars.sgf
reports that
H7 can be attacked at H2 (16 variations)
H7 can be defended at J1 (44 variations)
and the resulting variation tree looks very reasonable. This fixes
the problem at this move, although we could go on and analyze why
GNU thinks that F19 kills the top group.
Some caveats.
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Updated: $Date: 2006/11/23 10:12:40 $ $Author: ramprasadb $