Remove old zobrist trick for castling rights

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index c9db6224abfa2a160d5cf0777c15993a34e86f4b..6ef7aedc23f5c3aaa51402e127f07a4dac0b2a60 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -105,8 +105,7 @@ Key cuckoo[8192];
 Move cuckooMove[8192];
 
 
-/// Position::init() initializes at startup the various arrays used to compute
-/// hash keys.
+/// Position::init() initializes at startup the various arrays used to compute hash keys
 
 void Position::init() {
 
@@ -120,15 +119,7 @@ void Position::init() {
       Zobrist::enpassant[f] = rng.rand<Key>();
 
   for (int cr = NO_CASTLING; cr <= ANY_CASTLING; ++cr)
-  {
-      Zobrist::castling[cr] = 0;
-      Bitboard b = cr;
-      while (b)
-      {
-          Key k = Zobrist::castling[1ULL << pop_lsb(&b)];
-          Zobrist::castling[cr] ^= k ? k : rng.rand<Key>();
-      }
-  }
+      Zobrist::castling[cr] = rng.rand<Key>();
 
   Zobrist::side = rng.rand<Key>();
   Zobrist::noPawns = rng.rand<Key>();
@@ -781,9 +772,9 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
   // Update castling rights if needed
   if (st->castlingRights && (castlingRightsMask[from] | castlingRightsMask[to]))
   {
-      int cr = castlingRightsMask[from] | castlingRightsMask[to];
-      k ^= Zobrist::castling[st->castlingRights & cr];
-      st->castlingRights &= ~cr;
+      k ^= Zobrist::castling[st->castlingRights];
+      st->castlingRights &= ~(castlingRightsMask[from] | castlingRightsMask[to]);
+      k ^= Zobrist::castling[st->castlingRights];
   }
 
   // Move the piece. The tricky Chess960 castling is handled earlier
@@ -1112,6 +1103,7 @@ bool Position::see_ge(Move m, Value threshold) const {
   return bool(res);
 }
 
+
 /// Position::is_draw() tests whether the position is drawn by 50-move rule
 /// or by repetition. It does not detect stalemates.