X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fposition.cpp;h=b7baeb6b77d248128893fae25a411638d2805382;hp=b2d46b83a6a3b3d19494f2f0c424cd0df8188905;hb=74829342efcb93a6f581f69e293a02d3e2cfc507;hpb=4b926f227d00076439fbbc60e29c60403d992037

diff --git a/src/position.cpp b/src/position.cpp
index b2d46b83..b7baeb6b 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1015,22 +1015,27 @@ void Position::undo_null_move() {
   sideToMove = ~sideToMove;
 }
 
-// Position::hash_after_move() updates the hash key needed for the speculative prefetch.
-// It doesn't recognize special moves like castling, en-passant and promotions.
-Key Position::hash_after_move(Move m) const {
-
-  int from = from_sq(m);
-  int to = to_sq(m);
-  Piece p = board[from];
-  Piece capP = board[to];
-  Key ret = st->key ^ Zobrist::side;
-  if (capP != NO_PIECE)
-      ret ^= Zobrist::psq[color_of(capP)][type_of(capP)][to];
-  ret ^= Zobrist::psq[color_of(p)][type_of(p)][to];
-  ret ^= Zobrist::psq[color_of(p)][type_of(p)][from];
-  return ret;
+
+/// Position::key_after() computes the new hash key after the given moven. Needed
+/// for speculative prefetch. It doesn't recognize special moves like castling,
+/// en-passant and promotions.
+
+Key Position::key_after(Move m) const {
+
+  Color us = sideToMove;
+  Square from = from_sq(m);
+  Square to = to_sq(m);
+  PieceType pt = type_of(piece_on(from));
+  PieceType captured = type_of(piece_on(to));
+  Key k = st->key ^ Zobrist::side;
+
+  if (captured)
+      k ^= Zobrist::psq[~us][captured][to];
+
+  return k ^ Zobrist::psq[us][pt][to] ^ Zobrist::psq[us][pt][from];
 }
 
+
 /// Position::see() is a static exchange evaluator: It tries to estimate the
 /// material gain or loss resulting from a move.