Ticket #168: send2ret1.patch

engine/board.c

@@ -3310 +3310 @@
 }
 
 /*
+ * If (pos) has exactly one neighbor of color (color)
+ * returns position of this neighbor. Otherwise returns -1.
+ */
+
+int
+find_neighbor(int pos, int color)
+{
+  int npos;
+
+  ASSERT_ON_BOARD1(pos);
+  ASSERT1(IS_STONE(color), pos);
+
+  if (board[SOUTH(pos)] == color)
+    npos = SOUTH(pos);
+  else
+    npos = 0;
+  if (board[WEST(pos)] == color) {
+    if (npos)
+      npos = -1;
+    else
+      npos = WEST(pos);
+  }
+  if (board[NORTH(pos)] == color) {
+    if (npos)
+      npos = -1;
+    else
+      npos = NORTH(pos);
+  }
+  if (board[EAST(pos)] == color) {
+    if (npos)
+      npos = -1;
+    else
+      npos = EAST(pos);
+  }
+  return npos ? npos : -1;
+}
+
+/*
  * Returns true if str1_pos and str2_pos belong to the same string.
  */
 

engine/board.h

@@ -330 +330 @@
 int second_order_liberty_of_string(int pos, int str_pos);
 int neighbor_of_string(int pos, int str_pos);
 int has_neighbor(int pos, int color);
+int find_neighbor(int pos, int color);
 int same_string(int str1_pos, int str2_pos);
 int adjacent_strings(int str1_pos, int str2_pos);
 void mark_string(int str, signed char mx[BOARDMAX], signed char mark);

engine/reading.c

@@ -175 +175 @@
       int ko_move;                                                      \
       int apos = moves.pos[k];                                          \
                                                                         \
-      if (komaster_trymove(apos, other, moves.message[k], str,&ko_move, \
-                           stackp <= ko_depth && savecode == 0)) {      \
+      if ((board_ko_pos || !send_two_return_one(apos, other))           \
+          && komaster_trymove(apos, other,moves.message[k],str,&ko_move,\
+                              stackp <= ko_depth && savecode == 0)) {   \
         int dcode = do_find_defense(str, (defense_hint));               \
                                                                         \
         if (REVERSE_RESULT(dcode) > savecode                            \
@@ -1452 +1453 @@
 
   /* If the string is a single stone and a capture would give a ko,
    * try to defend it with ko by backfilling.
-   *
-   * FIXME: What is an example of this? Is it correct that the
-   *           return value is WIN and not KO_A or KO_B?
+   * If we don't find any defending move return LOSE and not KO_B,
+   * because we'll lose this ko sooner or later.
    */
   if (stackp <= backfill_depth
       && countstones(str) == 1

engine/utils.c

@@ -1434 +1434 @@
   int other = OTHER_COLOR(color);
   int lib1;
   int lib2;
+  int neighbor;
+
+  /* We must check this, because in such position:
+   *
+   * -----
+   * O.*OX
+   * OOXXX
+   *
+   * move * prevents making an eye by X player.
+   */
+  neighbor = find_neighbor(move, color);
+  if (neighbor == -1 || countlib(neighbor) != 2)
+    return 0;
 
   /* Try to play the move. */
   if (!trymove(move, color, "send_two_return_one-A", NO_MOVE))