Re: [gnugo-devel] owl goal dragon gets cut

[Gunnar Farnebäck]

Arend wrote:
> Say there were two strings, and they can be cut now. Then we compute the
> distance map from both strings (using the readconnect code), and build two
> components of the goal by assigning each stone to the string to which it is
> closer. The new goal is then the bigger of the two components.

It should probably not only take size into account but also where the
stones of the original dragon are.

> I would very much appreciate comments/ideas on this approach.

The trickiest part is of course to do this with reasonable
performance. Do you know how the node counters compare to CVS?

For what it's worth I made a failed, and not very ambitious, try to
solve this problem about a year ago. I don't remember whether the
results or the performance, or maybe both, was the problem. In case
that it can give some kind of inspiration, I include it below.

/Gunnar

Index: engine/owl.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/owl.c,v
retrieving revision 1.178
diff -u -r1.178 owl.c
--- engine/owl.c        10 Aug 2003 17:56:50 -0000      1.178
+++ engine/owl.c        9 Sep 2003 05:47:43 -0000
@@ -65,6 +65,7 @@
 
 struct local_owl_data {
   char goal[BOARDMAX];
+  int heart;
   char boundary[BOARDMAX];
 
   /* FIXME: escape_values[] are never recomputed. Consider moving this array
@@ -3634,6 +3635,7 @@
     }
 
   owl->color = color;
+  owl->heart = apos;
   owl_mark_boundary(owl);
 }
 
@@ -3824,6 +3826,22 @@
   && owl->boundary[pos2] < boundary_mark)
       mark_string(pos2, owl->boundary, boundary_mark);
   }
+
+  for (k = 0; k < 12; k++) {
+    int pos2 = pos + delta[k % 8];
+    if (k >= 8) {
+      if (!ON_BOARD(pos2))
+      continue;
+      else
+      pos2 += delta[k % 8];
+    }
+    
+    if (board[pos2] == OTHER_COLOR(board[pos])
+    && owl->goal[pos2] > 0
+    && disconnect(pos2, owl->heart, NULL) == WIN)
+      mark_string(pos2, owl->goal, (char) 0);
+  }
+
 }
 
 /* Lists the goal array. For use in GDB:
@@ -4910,6 +4928,8 @@
       }
     }
   }
+  owl->heart = libs[0];
+  
   /* FIXME: We would want to use init_owl() here too, but it doesn't
    * fit very well with the construction of the goal array above.
    */
@@ -5172,7 +5192,7 @@
   for (m = 0; m < board_size; m++) {
     for (n = 0; n < board_size; n++) {
       pos = POS(m, n);
-      if (dragon[pos].color == owl->color) {
+      if (dragon[pos].color == owl->color && !owl->goal[pos]) {
       if (dragon[pos].crude_status == ALIVE)
         owl->escape_values[pos] = 6;
         else if (dragon[pos].crude_status == UNKNOWN

@@ -5419,6 +5439,7 @@
 
   /* Copy the owl data. */
   memcpy(new_owl->goal, (*owl)->goal, sizeof(new_owl->goal));
+  new_owl->heart = (*owl)->heart;
   memcpy(new_owl->boundary, (*owl)->boundary, sizeof(new_owl->boundary));
   memcpy(new_owl->escape_values, (*owl)->escape_values,
    sizeof(new_owl->escape_values));