Remove the now redundant TT prefetch call from Position::do_move.

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index db4c857b0d25401cf97e3f70b56c8aeb10a46ee1..cbaa07e86e6c7925aa810347fc63688f63810252 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -25,12 +25,12 @@
 
 #include "bitcount.h"
 #include "movegen.h"
+#include "notation.h"
 #include "position.h"
 #include "psqtab.h"
 #include "rkiss.h"
 #include "thread.h"
 #include "tt.h"
-#include "notation.h"
 
 using std::string;
 
@@ -807,9 +807,6 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
       st->castlingRights &= ~cr;
   }
 
-  // Prefetch TT access as soon as we know the new hash key
-  prefetch((char*)TT.first_entry(k));
-
   // Move the piece. The tricky Chess960 castling is handled earlier
   if (type_of(m) != CASTLING)
       move_piece(from, to, us, pt);
@@ -1016,6 +1013,26 @@ void Position::undo_null_move() {
 }
 
 
+/// 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.