Speculative prefetch

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index b00bda24b0596b56a4661a315cfebc2e6c0195e0..b2d46b83a6a3b3d19494f2f0c424cd0df8188905 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1015,6 +1015,21 @@ 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::see() is a static exchange evaluator: It tries to estimate the
 /// material gain or loss resulting from a move.