Re: [gnugo-devel] reading patch

[Trevor Morris]

Um, on looking at this again, I do believe that it is correctly a
ko, and not unconditional.

To wit, in reading:154 - 
 B G4, W F2, B H2, W H3, B H4, W J2, B H1, W J4

A bit complicated, but none-the-less, it is a ko.

-Trevor


At 10:48 PM 10/26/2001 +0200, Gunnar Farneback wrote:
>This patch to reading.c solves the test case reading:154 and as a
>consequence trevor:3. I haven't run the rest of the regressions so I
>don't know whether it has additional effects.
>
>- break_chain2_efficient_moves() and break_chain2_moves() revised
>
>/Gunnar
>
>Index: engine/reading.c
>===================================================================
>RCS file: /cvsroot/gnugo/gnugo/engine/reading.c,v
>retrieving revision 1.26
>diff -u -r1.26 reading.c
>--- engine/reading.c   2001/10/26 07:21:11     1.26
>+++ engine/reading.c   2001/10/26 20:42:33
>@@ -4453,7 +4453,10 @@
> break_chain2_efficient_moves(int str, int moves[MAX_MOVES],
>                            int scores[MAX_MOVES], int *num_moves)
> {
>+  int color = board[str];
>+  int other = OTHER_COLOR(color);
>   int r;
>+  int k;
>   int adj, adjs[MAXCHAIN];
>   int adj2, adjs2[MAXCHAIN];
>   int libs[2];
>@@ -4477,10 +4480,10 @@
>       continue;
>     
>     findlib(adjs[r], 2, libs);
>-    if (approxlib(libs[0], board[adjs[r]], 3, NULL) <= 2)
>-      ADD_CANDIDATE_MOVE(libs[1], 0, moves, scores, *num_moves);
>-    if (approxlib(libs[1], board[adjs[r]], 3, NULL) <= 2)
>-      ADD_CANDIDATE_MOVE(libs[0], 0, moves, scores, *num_moves);
>+    for (k = 0; k < 2; k++)
>+      if (approxlib(libs[k], other, 3, NULL) <= 2
>+        && !is_self_atari(libs[1 - k], color))
>+      ADD_CANDIDATE_MOVE(libs[1 - k], 0, moves, scores, *num_moves);
>     
>     /* A common special case is this kind of edge position
>      * 
>@@ -4550,6 +4553,7 @@
>     for (k = 0; k < 2; k++) {
>       unsafe[k] = is_self_atari(libs[k], color);
>       if (!unsafe[k]
>+        || is_ko(libs[k], color, NULL)
>         || (!require_safe
>             && approxlib(libs[k], other, 5, NULL) < 5))
>       ADD_CANDIDATE_MOVE(libs[k], 0, moves, scores, *num_moves);
>
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