Re: [gnugo-devel] owl testcase (New Owl Defend Pattern)

[SP LEE]

> Evan wrote:
> > A simple owl testcase from a game today.
>
> A wonderful illustration why static eye analysis is so terribly
> difficult. The position in the lower right corner is this:
>
> . . X . O . . . . 8
> . O . X O . . . . 7
> . O X X X O . . . 6
> . O O X O O O O . 5
> . . . X X O X . O 4
> . O . X O O X . O 3
> . . O O X X . X X 2
> . . . . X . . . . 1
> L M N O P Q R S T
>
> I think it's clear that correct eye analysis in cases like this would
> require reading. Two questions appear:
>
> 1. How do we find relevant moves to read without getting a too slow
>    analysis?
> 2. What data structure would be appropriate for reading?
>
> /Gunnar
>
> PS If a white stone is added at O1 in the original position, there is
> still no way for white to kill all black stones in the corner,
> although it requires an under the stones tesuji to save black.

I would think it's hard to say what kind of eye R2 is. However, filling
a false eye is not always urgent. The following patch solves the problem
(owl1:320) by overruling the eye analysis decision. After run all the
regression test, there are several breakages.

ld_owl:20 Fail Correct critical (B3|A2|A6) (A2|B3), got critical B3 A4.
nngs3:740 pass
nngs4:740 pass

Surprisingly for ld_owl:20, A4 is also a good defense position, because
after A4, black can occupy either A6 or A2 to make 2 eyes. Therefore I
also made a patch for ld_owl.tst.

SP Lee

Index: owl_defendpats.db
===================================================================
RCS file: /cvsroot/gnugo/gnugo/patterns/owl_defendpats.db,v
retrieving revision 1.101
diff -u -r1.101 owl_defendpats.db
--- owl_defendpats.db 18 Jul 2003 18:59:22 -0000 1.101
+++ owl_defendpats.db 21 Aug 2003 16:44:30 -0000
@@ -3045,6 +3046,21 @@
 ---+

 ;!obvious_false_oeye(a)
+
+
+Pattern D804a
+#spl 3.5.1 owl 320
+
+|OO? defend eye in the corner
+|.*X
++---
+
+:8,-,value(75)
+
+|AA?
+|.*X
++---
+;lib(A) > 2


 Pattern D804b
Index: ld_owl.tst
===================================================================
RCS file: /cvsroot/gnugo/gnugo/regression/ld_owl.tst,v
retrieving revision 1.30
diff -u -r1.30 ld_owl.tst
--- ld_owl.tst 12 Aug 2003 03:02:56 -0000 1.30
+++ ld_owl.tst 21 Aug 2003 17:04:12 -0000
@@ -53,7 +53,7 @@
 19 dragon_status S2
 #? [critical (S3|T5) (S3|T5)]
 20 dragon_status B2
-#? [critical (B3|A2|A6) (A2|B3)]
+#? [critical (B3|A2|A6) (A2|A4|B3)]

 loadsgf games/life_and_death/ld6.sgf
 21 dragon_status B18