Fix repetition detection bug

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index 2b6e2b4c07a5e84640d839cd6aca37b77abf9f6d..0336a832a363291d4c07d5ade63899db790a9bca 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -356,8 +356,9 @@ void Position::print(Move m) const {
   std::cout << std::endl;
   if (m != MOVE_NONE)
   {
+      Position p(*this);
       string col = (color_of_piece_on(move_from(m)) == BLACK ? ".." : "");
-      std::cout << "Move is: " << col << move_to_san(*this, m) << std::endl;
+      std::cout << "Move is: " << col << move_to_san(p, m) << std::endl;
   }
   for (Rank rank = RANK_8; rank >= RANK_1; rank--)
   {
@@ -1300,6 +1301,11 @@ void Position::undo_null_move() {
 }
 
 
+///
+PieceType Position::captured_piece() const {
+  return st->capture;
+}
+
 /// Position::see() is a static exchange evaluator: It tries to estimate the
 /// material gain or loss resulting from a move. There are three versions of
 /// this function: One which takes a destination square as input, one takes a
@@ -1672,6 +1678,7 @@ Value Position::compute_non_pawn_material(Color c) const {
 /// Position::is_draw() tests whether the position is drawn by material,
 /// repetition, or the 50 moves rule. It does not detect stalemates, this
 /// must be done by the search.
+// FIXME: Currently we are not handling 50 move rule correctly when in check
 
 bool Position::is_draw() const {
 
@@ -1685,7 +1692,7 @@ bool Position::is_draw() const {
       return true;
 
   // Draw by repetition?
-  for (int i = 2; i < Min(Min(gamePly, st->rule50), st->pliesFromNull); i += 2)
+  for (int i = 4; i <= Min(Min(gamePly, st->rule50), st->pliesFromNull); i += 2)
       if (history[gamePly - i] == st->key)
           return true;