MovePicker: take advantage of threat move for ordering

[stockfish] / src / movepick.cpp

diff --git a/src/movepick.cpp b/src/movepick.cpp
index ee747c94525cdee18b9f78ea585abd3854cd23e8..ca0d8681a1d0515f4fc8c87110ab34124138ecd5 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -72,6 +72,7 @@ MovePicker::MovePicker(const Position& p, bool pv, Move ttm,
   mateKiller = (ss.mateKiller == ttm)? MOVE_NONE : ss.mateKiller;
   killer1 = ss.killers[0];
   killer2 = ss.killers[1];
+  threatMove = ss.threatMove;
   depth = d;
   movesPicked = 0;
   numOfMoves = 0;
@@ -270,10 +271,16 @@ void MovePicker::score_noncaptures() {
       else
           hs = H.move_ordering_score(pos.piece_on(move_from(m)), m);
 
-      // Ensure moves in history are always sorted as first
+      // If the null move was refuted by a capture then give a
+      // bonus if we move away the captured piece.
+      if (threatMove != MOVE_NONE && move_from(m) == move_to(threatMove))
+          hs *= 3;
+
+      // Ensure history is always preferred to pst
       if (hs > 0)
           hs += 1000;
 
+      // pst based scoring
       moves[i].score = hs + pos.mg_pst_delta(m);
   }
 }