Speedup see()

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index d58fdec1339cfffec3665c3830003824875ac310..0c81763155d078275263430b17b4a044269daeab 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -59,17 +59,18 @@ Key Position::exclusion_key() const { return st->key ^ Zobrist::exclusion;}
 
 namespace {
 
-// next_attacker() is an helper function used by see() to locate the least
+// min_attacker() is an helper function used by see() to locate the least
 // valuable attacker for the side to move, remove the attacker we just found
-// from the 'occupied' bitboard and scan for new X-ray attacks behind it.
+// from the bitboards and scan for new X-ray attacks behind it.
 
 template<int Pt> FORCE_INLINE
-PieceType next_attacker(const Bitboard* bb, const Square& to, const Bitboard& stmAttackers,
-                        Bitboard& occupied, Bitboard& attackers) {
+PieceType min_attacker(const Bitboard* bb, const Square& to, const Bitboard& stmAttackers,
+                       Bitboard& occupied, Bitboard& attackers) {
 
-  if (stmAttackers & bb[Pt])
+  Bitboard b = stmAttackers & bb[Pt];
+
+  if (b)
   {
-      Bitboard b = stmAttackers & bb[Pt];
       occupied ^= b & ~(b - 1);
 
       if (Pt == PAWN || Pt == BISHOP || Pt == QUEEN)
@@ -78,13 +79,15 @@ PieceType next_attacker(const Bitboard* bb, const Square& to, const Bitboard& st
       if (Pt == ROOK || Pt == QUEEN)
           attackers |= attacks_bb<ROOK>(to, occupied) & (bb[ROOK] | bb[QUEEN]);
 
+      attackers &= occupied; // Remove the just found attacker
+
       return (PieceType)Pt;
   }
-  return next_attacker<Pt+1>(bb, to, stmAttackers, occupied, attackers);
+  return min_attacker<Pt+1>(bb, to, stmAttackers, occupied, attackers);
 }
 
 template<> FORCE_INLINE
-PieceType next_attacker<KING>(const Bitboard*, const Square&, const Bitboard&, Bitboard&, Bitboard&) {
+PieceType min_attacker<KING>(const Bitboard*, const Square&, const Bitboard&, Bitboard&, Bitboard&) {
   return KING; // No need to update bitboards, it is the last cycle
 }
 
@@ -163,7 +166,7 @@ void Position::init() {
 
 Position& Position::operator=(const Position& pos) {
 
-  memcpy(this, &pos, sizeof(Position));
+  std::memcpy(this, &pos, sizeof(Position));
   startState = *st;
   st = &startState;
   nodes = 0;
@@ -690,9 +693,9 @@ bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
       Square rfrom = to; // 'King captures the rook' notation
       Square kto = relative_square(us, rfrom > kfrom ? SQ_G1 : SQ_C1);
       Square rto = relative_square(us, rfrom > kfrom ? SQ_F1 : SQ_D1);
-      Bitboard b = (pieces() ^ kfrom ^ rfrom) | rto | kto;
 
-      return attacks_bb<ROOK>(rto, b) & ksq;
+      return   (PseudoAttacks[ROOK][rto] & ksq)
+            && (attacks_bb<ROOK>(rto, (pieces() ^ kfrom ^ rfrom) | rto | kto) & ksq);
   }
   default:
       assert(false);
@@ -722,7 +725,7 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
   // Copy some fields of old state to our new StateInfo object except the ones
   // which are going to be recalculated from scratch anyway, then switch our state
   // pointer to point to the new, ready to be updated, state.
-  memcpy(&newSt, st, StateCopySize64 * sizeof(uint64_t));
+  std::memcpy(&newSt, st, StateCopySize64 * sizeof(uint64_t));
 
   newSt.previous = st;
   st = &newSt;
@@ -1089,7 +1092,7 @@ void Position::do_null_move(StateInfo& newSt) {
 
   assert(!checkers());
 
-  memcpy(&newSt, st, sizeof(StateInfo)); // Fully copy here
+  std::memcpy(&newSt, st, sizeof(StateInfo)); // Fully copy here
 
   newSt.previous = st;
   st = &newSt;
@@ -1198,10 +1201,8 @@ int Position::see(Move m, int asymmThreshold) const {
       swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured];
       slIndex++;
 
-      // Locate and remove from 'occupied' the next least valuable attacker
-      captured = next_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
-
-      attackers &= occupied; // Remove the just found attacker
+      // Locate and remove the next least valuable attacker
+      captured = min_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
       stm = ~stm;
       stmAttackers = attackers & pieces(stm);
 
@@ -1239,7 +1240,7 @@ int Position::see(Move m, int asymmThreshold) const {
 
 void Position::clear() {
 
-  memset(this, 0, sizeof(Position));
+  std::memset(this, 0, sizeof(Position));
   startState.epSquare = SQ_NONE;
   st = &startState;