[gnugo-devel] thrashing dragons

[Arend Bayer]

The thrashing dragon heuristic is currently only applied when the value
of the best move (without considering the thrashing dragon) is less than
10.0. Instead of this hardwired limit, I think it makes more sense to make
this proportional to our lead. If we are leading by 50 points, then there
is nothing wrong with constraining the thrashing dragon in preference to
a 20 point gote move, I would think.

Does anyone see a problem with this? Among other things, it will make
GNU Go much more willing to constrain thrashing dragons in high handicap
games, which seems like a good idea.

Arend

(A thrashing dragon is a dead group to which the opponent's last move
belongs, i.e. when the opponent probably thinks it is alive.)


nngs3:580       PASS H3 [H3|J5|K3|J3]
thrash:7        PASS D14 [D14]
thrash:8        PASS H10 [H10]
thrash:13       PASS P11 [P11]
kgs:450         PASS L15 [L15]
Total nodes: 1619562816 2972871 12882427

Index: engine/genmove.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/genmove.c,v
retrieving revision 1.94
diff -u -p -r1.94 genmove.c
--- engine/genmove.c    8 Sep 2004 17:03:42 -0000       1.94
+++ engine/genmove.c    16 Sep 2004 00:09:46 -0000
@@ -452,7 +452,7 @@ do_genmove(int *move, int color, float p
    * dragon dangerous and change its status from DEAD to
    * UNKNOWN. This may generate a move.
    */
-  if (val < 10.0 && !doing_scoring && !limit_search) {
+  if (val < 0.4 * our_score && !doing_scoring && !limit_search) {
     if (revise_thrashing_dragon(color, our_score, 15.0)) {
       shapes(color);
        f (!disable_endgame_patterns)