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Magic::index()

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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
This commit is contained in:
mstembera 2017-06-28 17:11:17 -07:00 • committed by Joona Kiiski
parent 7e897a64f2
commit 69eb391cd7
2 changed files with 21 additions and 22 deletions
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12
src/bitboard.cpp
View file

@ -54,9 +54,7 @@ namespace {
Bitboard RookTable[0x19000]; // To store rook attacks
Bitboard BishopTable[0x1480]; // To store bishop attacks
typedef unsigned (Fn)(const Magic&, Bitboard);
void init_magics(Bitboard table[], Magic magics[], Square deltas[], Fn index);
void init_magics(Bitboard table[], Magic magics[], Square deltas[]);
// bsf_index() returns the index into BSFTable[] to look up the bitscan. Uses
// Matt Taylor's folding for 32 bit case, extended to 64 bit by Kim Walisch.
@ -204,8 +202,8 @@ void Bitboards::init() {
Square RookDeltas[] = { NORTH, EAST, SOUTH, WEST };
Square BishopDeltas[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
init_magics(RookTable, RookMagics, RookDeltas, magic_index);
init_magics(BishopTable, BishopMagics, BishopDeltas, magic_index);
init_magics(RookTable, RookMagics, RookDeltas);
init_magics(BishopTable, BishopMagics, BishopDeltas);
for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
{
@ -251,7 +249,7 @@ namespace {
// chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we
// use the so called "fancy" approach.
void init_magics(Bitboard table[], Magic magics[], Square deltas[], Fn index) {
void init_magics(Bitboard table[], Magic magics[], Square deltas[]) {
int seeds[][RANK_NB] = { { 8977, 44560, 54343, 38998, 5731, 95205, 104912, 17020 },
{ 728, 10316, 55013, 32803, 12281, 15100, 16645, 255 } };
@ -311,7 +309,7 @@ namespace {
// m.attacks[] after every failed attempt.
for (++cnt, i = 0; i < size; ++i)
{
unsigned idx = index(m, occupancy[i]);
unsigned idx = m.index(occupancy[i]);
if (epoch[idx] < cnt)
{

31
src/bitboard.h
View file

@ -82,6 +82,20 @@ struct Magic {
Bitboard magic;
Bitboard* attacks;
unsigned shift;
/// looks up the index using the 'magic bitboards' approach.
unsigned index(Bitboard occupied) const {
if (HasPext)
return unsigned(pext(occupied, mask));
if (Is64Bit)
return unsigned(((occupied & mask) * magic) >> shift);
unsigned lo = unsigned(occupied) & unsigned(mask);
unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
}
};
extern Magic RookMagics[SQUARE_NB];
@ -222,26 +236,13 @@ template<> inline int distance<Rank>(Square x, Square y) { return distance(rank_
/// attacks_bb() returns a bitboard representing all the squares attacked by a
/// piece of type Pt (bishop or rook) placed on 's'. The helper magic_index()
/// looks up the index using the 'magic bitboards' approach.
inline unsigned magic_index(const Magic& m, Bitboard occupied) {
if (HasPext)
return unsigned(pext(occupied, m.mask));
if (Is64Bit)
return unsigned(((occupied & m.mask) * m.magic) >> m.shift);
unsigned lo = unsigned(occupied) & unsigned(m.mask);
unsigned hi = unsigned(occupied >> 32) & unsigned(m.mask >> 32);
return (lo * unsigned(m.magic) ^ hi * unsigned(m.magic >> 32)) >> m.shift;
}
/// piece of type Pt (bishop or rook) placed on 's'.
template<PieceType Pt>
inline Bitboard attacks_bb(Square s, Bitboard occupied) {
const Magic& M = Pt == ROOK ? RookMagics[s] : BishopMagics[s];
return M.attacks[magic_index(M, occupied)];
return M.attacks[M.index(occupied)];
}
inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {