Re: [gnugo-devel] Comments on lazarus.tst

[Gunnar Farneback]

Dan wrote:
> Maybe we should allow P8 but on the other hand P8 over Q8 seems
> to typify one of GNU Go's weaknesses, which is a failure to
> simplify the position.

I don't think it's worth regressing over this distinction in this test
case. There are lots of better examples of that problem.

> > I think the upper right is dead as it stands. I've put variations in
> > the sgf-file below.
> 
> I don't think so.

Me neither.

> Instead of attacking the 5 nakade stones at T8, W can attack at T6. This
> gives W a live eye shape.

Interestingly enough, GNU Go does exactly the same mistake. The appended
patch fixes the problem.

/Gunnar

Index: engine/optics.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/optics.c,v
retrieving revision 1.35
diff -u -r1.35 optics.c
--- engine/optics.c     11 Jan 2002 01:38:37 -0000      1.35
+++ engine/optics.c     15 Jan 2002 11:35:59 -0000
@@ -1244,8 +1244,19 @@
        }
        
        gg_assert(num_attacks > 0 && num_defenses > 0);
+
        *attack_point = attack_points[0];
+       /* If possible, choose a non-sacrificial defense point.
+         * Compare white T8 and T6 in lazarus:21.
+        */
        *defense_point = defense_points[0];
+       for (k = 0; k < num_defenses; k++) {
+         if (safe_move(defense_points[k], eye_color) == WIN) {
+           *defense_point = defense_points[k];
+           break;
+         }
+       }
+       
        DEBUG(DEBUG_EYES, "  vital points: %1m (attack) %1m (defense)\n",
              *attack_point, *defense_point);
        DEBUG(DEBUG_EYES, "  pattern matched:  %s\n", graphs[graph].patname);
Index: patterns/eyes.db
===================================================================
RCS file: /cvsroot/gnugo/gnugo/patterns/eyes.db,v
retrieving revision 1.16
diff -u -r1.16 eyes.db
--- patterns/eyes.db    9 Jan 2002 01:01:32 -0000       1.16
+++ patterns/eyes.db    15 Jan 2002 11:36:00 -0000
@@ -2540,6 +2540,15 @@
 
 Pattern 7202
 
+ X
+XX*
+ XX>
+
+:2,1
+
+
+Pattern 7203
+
  x
 xX*
  XX.
@@ -2547,7 +2556,7 @@
 :2,1
 
 
-Pattern 7203
+Pattern 7204
 
  x
 xXX