Re: [gnugo-devel] Re: [gtp] Re: resignation support in clients?

[Gunnar Farnebäck]

I wrote (on September 2):
> In the special case where GNU Go finds that all its stones are dead
> and the "thrash around for a while anyway" patterns don't kick in it
> would at least be very natural to resign rather than pass. It should
> be an easy patch.

It wasn't easy until I changed the genmove() interface, but now it is.
This patch also changes the lively_dragon_exists() function to be
based on status instead of crude_status. As far as I can tell it
wasn't intentional that it used crude_status but an oversight when the
old status field was renamed to crude_status.

- resign rather than pass when all own stones seem dead
- lively_dragon_exists() based on status rather than crude_status

/Gunnar

Index: engine/dragon.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/dragon.c,v
retrieving revision 1.143
diff -u -r1.143 dragon.c
--- engine/dragon.c     13 Sep 2004 10:45:11 -0000      1.143
+++ engine/dragon.c     9 Nov 2004 20:23:05 -0000
@@ -494,7 +494,7 @@
   lively_white_dragons = 0;
   lively_black_dragons = 0;
   for (d = 0; d < number_of_dragons; d++)
-    if (DRAGON(d).crude_status != DEAD) {
+    if (DRAGON(d).status != DEAD) {
       if (DRAGON(d).color == WHITE)
         lively_white_dragons++;
       else
Index: engine/genmove.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/genmove.c,v
retrieving revision 1.96
diff -u -r1.96 genmove.c
--- engine/genmove.c    8 Nov 2004 04:10:02 -0000       1.96
+++ engine/genmove.c    9 Nov 2004 20:23:05 -0000
@@ -54,7 +54,7 @@
 
 static void break_mirror_go(int color);
 static int find_mirror_move(int *move, int color);
-static int should_resign(int color, float our_score);
+static int should_resign(int color, float our_score, int move);
 
 void sgfShowConsideredMoves(void);
 
@@ -533,13 +533,14 @@
   }
   else {
     TRACE("genmove() recommends %1m with value %f\n", move, *value);
-    /* Maybe time to resign...
-     */
-    if (resign && resign_allowed
-       && *value < 10.0 && should_resign(color, our_score)) {
-      TRACE("... though, genmove() thinks the position is hopeless\n");
-      *resign = 1;
-    }
+  }
+  
+  /* Maybe time to resign...
+   */
+  if (resign && resign_allowed
+      && *value < 10.0 && should_resign(color, our_score, move)) {
+    TRACE("... though, genmove() thinks the position is hopeless\n");
+    *resign = 1;
   }
   
   /* If statistics is turned on, this is the place to show it. */
@@ -743,16 +744,24 @@
 /* Helper to decide whether GG should resign a game
  */
 static int
-should_resign(int color, float our_score)
+should_resign(int color, float our_score, int move)
 {
   float status;
   int d;
   /* We resign 19x19 games only, smaller board games are fast enough.
    * We resign only if the margin is bigger than 45 pts and if we are
    * behind (of course).
+   *
+   * As an exception to this rule, we resign on any board size if
+   * it looks like all our dragons are dead and the generated move
+   * is a pass.
    */
-  if (board_size < 19
-      || our_score > -45.0) 
+  if (move == PASS_MOVE && !lively_dragon_exists(color))
+    return 1;
+  
+  if (move != PASS_MOVE
+      || board_size < 19
+      || our_score > -45.0)
     return 0;
   /* Check dragon statuses. If a friendly dragon is critical, we are
    * possibly not that much behind after we save it. If some hostile
Index: patterns/helpers.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/patterns/helpers.c,v
retrieving revision 1.63
diff -u -r1.63 helpers.c
--- patterns/helpers.c  8 Sep 2004 17:03:42 -0000       1.63
+++ patterns/helpers.c  9 Nov 2004 20:23:05 -0000
@@ -763,14 +763,10 @@
   if (doing_scoring
       || (stones_on_board(BLACK | WHITE) > board_size * board_size * 2 / 5
          && stones_on_board(WHITE) > board_size * board_size / 5)
-      || color == BLACK)
+      || color == BLACK
+      || lively_dragon_exists(WHITE))
     return 0;
 
-  for (d = 0; d < number_of_dragons; d++)
-    if (DRAGON(d).color == WHITE
-       && DRAGON(d).status != DEAD)
-      return 0;
-
   return 1;
 }