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Speedup see()

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And rename next_attacker() SEE helper

This very simple patch is able to speed up
bench run of almost 2% !

No functional change.
This commit is contained in:
Marco Costalba 2013-07-20 11:44:55 +02:00
parent a5b5a91512
commit 0504a6975d
1 changed files with 13 additions and 12 deletions
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25
src/position.cpp
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@ -59,17 +59,18 @@ Key Position::exclusion_key() const { return st->key ^ Zobrist::exclusion;}
namespace { 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 // 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 template<int Pt> FORCE_INLINE
PieceType next_attacker(const Bitboard* bb, const Square& to, const Bitboard& stmAttackers, PieceType min_attacker(const Bitboard* bb, const Square& to, const Bitboard& stmAttackers,
Bitboard& occupied, Bitboard& attackers) { Bitboard& occupied, Bitboard& attackers) {
if (stmAttackers & bb[Pt]) Bitboard b = stmAttackers & bb[Pt];
if (b)
{ {
Bitboard b = stmAttackers & bb[Pt];
occupied ^= b & ~(b - 1); occupied ^= b & ~(b - 1);
if (Pt == PAWN || Pt == BISHOP || Pt == QUEEN) 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) if (Pt == ROOK || Pt == QUEEN)
attackers |= attacks_bb<ROOK>(to, occupied) & (bb[ROOK] | bb[QUEEN]); attackers |= attacks_bb<ROOK>(to, occupied) & (bb[ROOK] | bb[QUEEN]);
attackers &= occupied; // Remove the just found attacker
return (PieceType)Pt; 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 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 return KING; // No need to update bitboards, it is the last cycle
} }
@ -1198,10 +1201,8 @@ int Position::see(Move m, int asymmThreshold) const {
swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured]; swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured];
slIndex++; slIndex++;
// Locate and remove from 'occupied' the next least valuable attacker // Locate and remove the next least valuable attacker
captured = next_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers); captured = min_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
attackers &= occupied; // Remove the just found attacker
stm = ~stm; stm = ~stm;
stmAttackers = attackers & pieces(stm); stmAttackers = attackers & pieces(stm);