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Greatly speed up SEE

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Simply reshuffling the code inverting the condition in next_attacker()
yields a miraculous speed up of more than 3% under gcc!

On my laptop a bench run goes from 320Knps to 330Knps

No functional change.
This commit is contained in:
Marco Costalba
2012-09-02 00:15:27 +02:00
parent 9cdca7516c
commit e6d8e74152
1 changed files with 17 additions and 17 deletions
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34
src/position.cpp
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@@ -106,25 +106,24 @@ void init() {
/// valuable attacker for the side to move, remove the attacker we just found /// 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 'occupied' bitboard and scan for new X-ray attacks behind it.
template<PieceType Pt> static FORCE_INLINE template<int Pt> static FORCE_INLINE
PieceType next_attacker(const Bitboard* bb, const Square& to, const Bitboard& stmAttackers, PieceType next_attacker(const Bitboard* bb, const Square& to, const Bitboard& stmAttackers,
Bitboard& occupied, Bitboard& attackers) { Bitboard& occupied, Bitboard& attackers) {
const PieceType NextPt = PieceType((int)Pt + 1); if (stmAttackers & bb[Pt])
{
Bitboard b = stmAttackers & bb[Pt];
occupied ^= b & ~(b - 1);
if (!(stmAttackers & bb[Pt])) if (Pt == PAWN || Pt == BISHOP || Pt == QUEEN)
return next_attacker<NextPt>(bb, to, stmAttackers, occupied, attackers); attackers |= attacks_bb<BISHOP>(to, occupied) & (bb[BISHOP] | bb[QUEEN]);
Bitboard b = stmAttackers & bb[Pt]; if (Pt == ROOK || Pt == QUEEN)
occupied ^= b & ~(b - 1); attackers |= attacks_bb<ROOK>(to, occupied) & (bb[ROOK] | bb[QUEEN]);
if (Pt == PAWN || Pt == BISHOP || Pt == QUEEN) return (PieceType)Pt;
attackers |= attacks_bb<BISHOP>(to, occupied) & (bb[BISHOP] | bb[QUEEN]); }
return next_attacker<Pt+1>(bb, to, stmAttackers, occupied, attackers);
if (Pt == ROOK || Pt == QUEEN)
attackers |= attacks_bb<ROOK>(to, occupied) & (bb[ROOK] | bb[QUEEN]);
return Pt;
} }
template<> FORCE_INLINE template<> FORCE_INLINE
@@ -1312,11 +1311,12 @@ int Position::see(Move m) const {
stm = ~stm; stm = ~stm;
stmAttackers = attackers & pieces(stm); stmAttackers = attackers & pieces(stm);
// Stop before processing a king capture if (captured == KING)
if (captured == KING && stmAttackers)
{ {
assert(slIndex < 32); // Stop before processing a king capture
swapList[slIndex++] = QueenValueMg * 16; if (stmAttackers)
swapList[slIndex++] = QueenValueMg * 16;
break; break;
} }