Re: [gnugo-devel] bug report

[Gunnar Farnebäck]

I wrote:
> There are at least two ways to fix this bug:
> 1. Change safe_move() to not cache results when reading at reduced
>    depth. The main difficulty with this is that we currently have no
>    way to detect reduced depth.

Implemented below. Fixes the crash.

- new global variable depth_offset
- only cache safe_move() results when reading depth is unmodified

/Gunnar

Index: engine/globals.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/globals.c,v
retrieving revision 1.67
diff -u -r1.67 globals.c
--- engine/globals.c    8 Jun 2004 05:06:12 -0000       1.67
+++ engine/globals.c    3 Nov 2004 21:18:07 -0000
@@ -49,6 +49,7 @@
 int ko_depth;           /* deep reading cut off */
 int branch_depth;       /* deep reading cut off */
 int aa_depth;
+int depth_offset;       /* keeps track of temporary depth changes */
 int owl_distrust_depth;   /* below this owl trusts the optics code */
 int owl_branch_depth;     /* below this owl tries only one variation */
 int owl_reading_depth;    /* owl does not read below this depth */
Index: engine/liberty.h
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/liberty.h,v
retrieving revision 1.228
diff -u -r1.228 liberty.h
--- engine/liberty.h    11 Oct 2004 21:03:28 -0000      1.228
+++ engine/liberty.h    3 Nov 2004 21:18:07 -0000
@@ -719,6 +719,7 @@
 extern int fourlib_depth;       /* deep reading cutoff */
 extern int ko_depth;            /* deep ko reading cutoff */
 extern int aa_depth;            /* deep global reading cutoff */
+extern int depth_offset;        /* keeps track of temporary depth changes */
 extern int owl_distrust_depth;  /* below this owl trusts the optics code */
 extern int owl_branch_depth;    /* below this owl tries only one variation */
 extern int owl_reading_depth;   /* owl does not read below this depth */
Index: engine/reading.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/reading.c,v
retrieving revision 1.152
diff -u -r1.152 reading.c
--- engine/reading.c    8 Sep 2004 17:03:42 -0000       1.152
+++ engine/reading.c    3 Nov 2004 21:18:07 -0000
@@ -5558,8 +5558,12 @@
     initialized = 1;
   }
 
-  /* If we have this position cached, use the previous value. */
+  /* If we have this position cached, use the previous value.
+   * Only use cached values when stackp is 0 and reading is not being done
+   * at a modified depth.
+   */
   if (stackp == 0
+      && depth_offset == 0
       && safe_move_cache_when[move][color == BLACK] == position_number)
     return safe_move_cache[move][color == BLACK];
 
@@ -5578,7 +5582,7 @@
    * Comment: This is currently not a problem since no reduced depth
    * reading is performed.
    */
-  if (stackp == 0) {
+  if (stackp == 0 && depth_offset == 0) {
     if (0)
       gprintf("Safe move at %1m for %s cached when depth=%d, position 
number=%d\n",
              move, color_to_string(color), depth, position_number);
Index: engine/utils.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/utils.c,v
retrieving revision 1.97
diff -u -r1.97 utils.c
--- engine/utils.c      8 Sep 2004 17:03:42 -0000       1.97
+++ engine/utils.c      3 Nov 2004 21:18:08 -0000
@@ -806,6 +806,8 @@
   if (mandated_owl_node_limit != -1)
     owl_node_limit = mandated_owl_node_limit;
 
+  depth_offset = 0;
+  
   if (report_levels) {
     fprintf(stderr, "at level %d:\n\n\
 depth: %d\n\
@@ -861,6 +863,7 @@
   fourlib_depth      += n;
   ko_depth           += n;
   breakin_depth             += n;
+  depth_offset       += n;
 }
 
 void