Simplify SEE Pruning (#2191)

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index b8d7b1068b2f462a494a1c3165fff8b4caec5e52..14121d47af67dd234c5f04134328a9c895654717 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -387,7 +387,7 @@ void Position::set_state(StateInfo* si) const {
       if (type_of(pc) == PAWN)
           si->pawnKey ^= Zobrist::psq[pc][s];
 
-      else if (type_of(pc) != PAWN && type_of(pc) != KING)
+      else if (type_of(pc) != KING)
           si->nonPawnMaterial[color_of(pc)] += PieceValue[MG][pc];
   }
 
@@ -491,7 +491,7 @@ Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners
   // Snipers are sliders that attack 's' when a piece and other snipers are removed
   Bitboard snipers = (  (PseudoAttacks[  ROOK][s] & pieces(QUEEN, ROOK))
                       | (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders;
-  Bitboard occupancy = pieces() & ~snipers;
+  Bitboard occupancy = pieces() ^ snipers;
 
   while (snipers)
   {
@@ -1189,16 +1189,13 @@ bool Position::has_game_cycle(int ply) const {
 
           if (!(between_bb(s1, s2) & pieces()))
           {
-              // In the cuckoo table, both moves Rc1c5 and Rc5c1 are stored in the same
-              // location. We select the legal one by reversing the move variable if necessary.
-              if (empty(s1))
-                  move = make_move(s2, s1);
-
               if (ply > i)
                   return true;
 
-              // For nodes before or at the root, check that the move is a repetition one
-              // rather than a move to the current position
+              // For nodes before or at the root, check that the move is a
+              // repetition rather than a move to the current position.
+              // In the cuckoo table, both moves Rc1c5 and Rc5c1 are stored in
+              // the same location, so we have to select which square to check.
               if (color_of(piece_on(empty(s1) ? s2 : s1)) != side_to_move())
                   continue;