Replace MVV/LVA by MVV for good captures

Passed STC

LLR: 3.71 (-2.94,2.94) [-3.00,1.00]
Total: 64363 W: 12299 L: 12214 D: 39850

and LTC

LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 69976 W: 11056 L: 11011 D: 47909

Bench: 8012532

Resolves #340

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 190a30f8c8c613f22dcd8351ed3609ce1ac66986..9656e5e64ddfd912aa694fcffef4c4edc271916e 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -134,10 +134,10 @@ MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, const
 /// highest values will be picked first.
 template<>
 void MovePicker::score<CAPTURES>() {
-  // Winning and equal captures in the main search are ordered by MVV/LVA.
+  // Winning and equal captures in the main search are ordered by MVV.
   // Suprisingly, this appears to perform slightly better than SEE based
   // move ordering. The reason is probably that in a position with a winning
-  // capture, capturing a more valuable (but sufficiently defended) piece
+  // capture, capturing a valuable (but sufficiently defended) piece
   // first usually doesn't hurt. The opponent will have to recapture, and
   // the hanging piece will still be hanging (except in the unusual cases
   // where it is possible to recapture with the hanging piece). Exchanging
@@ -148,15 +148,7 @@ void MovePicker::score<CAPTURES>() {
   // has been picked up in pick_move_from_list(). This way we save some SEE
   // calls in case we get a cutoff.
   for (auto& m : *this)
-      if (type_of(m) == ENPASSANT)
-          m.value = PieceValue[MG][PAWN] - Value(PAWN);
-
-      else if (type_of(m) == PROMOTION)
-          m.value =  PieceValue[MG][pos.piece_on(to_sq(m))] - Value(PAWN)
-                   + PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN];
-      else
-          m.value =  PieceValue[MG][pos.piece_on(to_sq(m))]
-                   - Value(type_of(pos.moved_piece(m)));
+      m.value =  Value(int(pos.piece_on(to_sq(m))));
 }
 
 template<>