Re: [gnugo-devel] Computing illegal influence

[Gunnar Farneback]

Arend wrote:
> This happens at move 263 (the move number is misleading). You can reproduce
> it with 
> 
> loadsgf game.sgf 261
> genmove_white
> black K2
> genmove_white
> 
> The trace output directly before the above message is
>   J2: owl attack/defend for E7
>   J2: owl attack/defend for F2
> 
> This is due to the persistent owl cache entry below.

This patch should solve the problem, but I haven't actually tested it.
In any case this bug shouldn't do any real harm, so it may be better
to save the patch for post 3.2.

- store_persistent_owl_cache() revised

/Gunnar

Index: engine/owl.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/owl.c,v
retrieving revision 1.83
diff -u -r1.83 owl.c
--- engine/owl.c        20 Apr 2002 20:41:53 -0000      1.83
+++ engine/owl.c        22 Apr 2002 20:48:36 -0000
@@ -4792,6 +4792,7 @@
   if (ON_BOARD1(move2))
     active[move2] = 1;
 
+  /* Distance four expansion through empty intersections and own stones. */
   for (k = 1; k < 5; k++) {
     for (pos = BOARDMIN; pos < BOARDMAX; pos++){
       if (!ON_BOARD(pos) || board[pos] == other || active[pos] != 0) 
@@ -4808,18 +4809,23 @@
     }
   }
   
+  /* Adjacent opponent strings. */
   for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
     if (board[pos] != other || active[pos] != 0) 
       continue;
     for (r = 0; r < 4; r++) {
       int pos2 = pos + delta[r];
       if (ON_BOARD(pos2) && board[pos2] != other && active[pos2] != 0) {
-       active[pos] = 1;
+       mark_string(pos, active, (char) 1);
        break;
       }
     }
   }
   
+  /* Liberties of adjacent opponent strings with less than five liberties +
+   * liberties of low liberty neighbors of adjacent opponent strings
+   * with less than five liberties.
+   */
   for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
     if (board[pos] == other && active[pos] != 0 && countlib(pos) < 5) {
       int libs[4];