[gnugo-devel] More on minimum values

[Evan Berggren Daniel]

I decided to look a little bit more at minimum values.  After some
thinking, I decided that making the minimum value parameter a soft minimum
made more sense than pushing values above it.  In order to find out how
big a change this made to playing strength, I ran a 100 game series
between the unpatched and patched versions.  The patched version won 67 to
33.

I think this suggests there is a substantial negative impact as a result
of minimum values in their current form.  I don't have a great solution to
propose that solves the problem while keeping some randomness to joseki
choice for the sake of variation.  I think the patch in its current form
is reasonable though not ideal, and better than the previous versions.

The games are available at http://evand.rh.ncsu.edu/~evand/minval.tar.gz

Thanks

Evan Daniel


Index: engine/value_moves.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/value_moves.c,v
retrieving revision 1.81
diff -u -d -r1.81 value_moves.c
--- engine/value_moves.c        1 Feb 2003 10:31:50 -0000       1.81
+++ engine/value_moves.c        15 Feb 2003 01:17:14 -0000
@@ -2686,7 +2686,8 @@
     move[pos].min_value += tot_value / 200;
   if (tot_value < move[pos].min_value
       && move[pos].min_value > 0) {
-    tot_value = move[pos].min_value;
+    tot_value = move[pos].min_value - 2 +
+           (2 * tot_value / move[pos].min_value);
     TRACE("  %1m:   %f - minimum accepted value\n", pos, tot_value);
   }


Full results:

W+18.5
W+4.5
B+13.5
B+12.5
B+18.5
W+2.5
W+5.5
W+5.5
B+23.5
W+10.5
B+2.5
B+14.5
W+17.5
B+12.5
W+19.5
W+15.5
B+8.5
B+31.5
B+1.5
B+10.5
W+48.5
B+1.5
B+22.5
B+12.5
B+6.5
W+21.5
B+35.5
B+39.5
B+62.5
B+39.5
B+22.5
B+28.5
B+39.5
B+0.5
W+1.5
B+5.5
B+11.5
B+55.5
B+12.5
W+2.5
B+45.5
W+1.5
B+18.5
B+41.5
B+35.5
B+20.5
B+42.5
W+5.5
B+21.5
B+1.5
W+1.5
B+3.5
B+89.5
W+4.5
B+29.5
B+2.5
B+8.5
W+12.5
W+37.5
B+18.5
B+9.5
W+24.5
B+25.5
W+8.5
W+9.5
B+29.5
B+24.5
B+16.5
B+7.5
B+15.5
B+16.5
B+5.5
W+22.5
B+21.5
B+17.5
B+13.5
W+20.5
B+41.5
B+22.5
B+42.5
B+0.5
W+23.5
B+14.5
W+19.5
W+39.5
B+28.5
W+12.5
B+37.5
W+7.5
W+1.5
B+2.5
W+14.5
B+6.5
B+28.5
B+2.5
W+0.5
B+23.5
B+29.5
W+12.5
B+14.5