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Magic::index()
Make magic_index() a member of Magic since it uses all it's members and keep us from having to pass the function pointer around to init_magics(). No functional change Closes #1146
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2 changed files with 21 additions and 22 deletions
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@ -54,9 +54,7 @@ namespace {
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Bitboard RookTable[0x19000]; // To store rook attacks
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Bitboard BishopTable[0x1480]; // To store bishop attacks
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typedef unsigned (Fn)(const Magic&, Bitboard);
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void init_magics(Bitboard table[], Magic magics[], Square deltas[], Fn index);
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void init_magics(Bitboard table[], Magic magics[], Square deltas[]);
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// bsf_index() returns the index into BSFTable[] to look up the bitscan. Uses
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// Matt Taylor's folding for 32 bit case, extended to 64 bit by Kim Walisch.
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@ -204,8 +202,8 @@ void Bitboards::init() {
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Square RookDeltas[] = { NORTH, EAST, SOUTH, WEST };
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Square BishopDeltas[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
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init_magics(RookTable, RookMagics, RookDeltas, magic_index);
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init_magics(BishopTable, BishopMagics, BishopDeltas, magic_index);
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init_magics(RookTable, RookMagics, RookDeltas);
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init_magics(BishopTable, BishopMagics, BishopDeltas);
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for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
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{
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@ -251,7 +249,7 @@ namespace {
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// chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we
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// use the so called "fancy" approach.
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void init_magics(Bitboard table[], Magic magics[], Square deltas[], Fn index) {
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void init_magics(Bitboard table[], Magic magics[], Square deltas[]) {
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int seeds[][RANK_NB] = { { 8977, 44560, 54343, 38998, 5731, 95205, 104912, 17020 },
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{ 728, 10316, 55013, 32803, 12281, 15100, 16645, 255 } };
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@ -311,7 +309,7 @@ namespace {
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// m.attacks[] after every failed attempt.
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for (++cnt, i = 0; i < size; ++i)
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{
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unsigned idx = index(m, occupancy[i]);
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unsigned idx = m.index(occupancy[i]);
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if (epoch[idx] < cnt)
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{
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@ -82,6 +82,20 @@ struct Magic {
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Bitboard magic;
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Bitboard* attacks;
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unsigned shift;
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/// looks up the index using the 'magic bitboards' approach.
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unsigned index(Bitboard occupied) const {
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if (HasPext)
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return unsigned(pext(occupied, mask));
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if (Is64Bit)
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return unsigned(((occupied & mask) * magic) >> shift);
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unsigned lo = unsigned(occupied) & unsigned(mask);
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unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
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return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
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}
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};
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extern Magic RookMagics[SQUARE_NB];
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@ -222,26 +236,13 @@ template<> inline int distance<Rank>(Square x, Square y) { return distance(rank_
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/// attacks_bb() returns a bitboard representing all the squares attacked by a
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/// piece of type Pt (bishop or rook) placed on 's'. The helper magic_index()
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/// looks up the index using the 'magic bitboards' approach.
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inline unsigned magic_index(const Magic& m, Bitboard occupied) {
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if (HasPext)
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return unsigned(pext(occupied, m.mask));
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if (Is64Bit)
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return unsigned(((occupied & m.mask) * m.magic) >> m.shift);
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unsigned lo = unsigned(occupied) & unsigned(m.mask);
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unsigned hi = unsigned(occupied >> 32) & unsigned(m.mask >> 32);
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return (lo * unsigned(m.magic) ^ hi * unsigned(m.magic >> 32)) >> m.shift;
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}
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/// piece of type Pt (bishop or rook) placed on 's'.
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template<PieceType Pt>
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inline Bitboard attacks_bb(Square s, Bitboard occupied) {
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const Magic& M = Pt == ROOK ? RookMagics[s] : BishopMagics[s];
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return M.attacks[magic_index(M, occupied)];
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return M.attacks[M.index(occupied)];
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}
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inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
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