[gnugo-devel] reading patch

[Gunnar Farneback]

This patch to reading.c solves test case reading:171. The total
regression delta is:

./regress.sh . reading.tst 
171 unexpected PASS!
./regress.sh . rosebud.tst 
1 unexpected PASS!
./regress.sh . lazarus.tst
5 unexpected FAIL: Correct 'R13', got 'N11'
14 unexpected FAIL: Correct 'Q15|T5|H5', got 'Q14'
./regress.sh . nicklas4.tst
1201 unexpected PASS!
./regress.sh . global.tst
34 unexpected FAIL: Correct 'N6', got 'L6'

Two of the three failures seem to be purely accidental. In lazarus:5
the difference is that an owl defense for P10 is found at N11, which
doesn't exactly look unreasonable. In lazarus:14 the difference is
that Q19 and O14 become amalgamated, which they clearly should be.

In global:34 the difference is that neither O6 nor M8 is considered
owl defendable any more. This looks tricky to determine and may
involve semeai considerations.

- break_chain2_moves() revised

/Gunnar

Index: engine/reading.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/reading.c,v
retrieving revision 1.66
diff -u -r1.66 reading.c
--- engine/reading.c    4 Jul 2002 19:33:00 -0000       1.66
+++ engine/reading.c    20 Aug 2002 20:45:35 -0000
@@ -4628,6 +4628,7 @@
   int apos;
   int adj;
   int adjs[MAXCHAIN];
+  int dummy_adjs[MAXCHAIN];
   int libs[2];
   int unsafe[2];
 
@@ -4636,6 +4637,18 @@
   for (r = 0; r < adj; r++) {
     apos = adjs[r];
 
+    /* If stackp > backfill_depth, don't bother playing liberties of
+     * 2-liberty strings if those also have at least one neighbor in
+     * atari. This is intended to solve reading:171 and generally reduce
+     * the number of nodes.
+     *
+     * FIXME: We may need to still accept these moves if they happen to
+     * take the ataried string out of atari.
+     */
+    if (stackp > backfill_depth
+       && chainlinks2(apos, dummy_adjs, 1) > 0)
+      continue;
+      
     findlib(apos, 2, libs);
     for (k = 0; k < 2; k++) {
       unsafe[k] = is_self_atari(libs[k], color);