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Reordering magic data

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Gather all magic relevant data into a struct.

This changes memory layout putting everything necessary for processing a single square
in the same memory location thus speeding up access.

Original patch by @snicolet

No functional change.

Closes #1127
Closes #1128
This commit is contained in:
mstembera 2017-06-06 10:20:43 -07:00 • committed by Joona Kiiski
parent 6d89d0b64a
commit 659990b43f
2 changed files with 39 additions and 42 deletions
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41
src/bitboard.cpp
View file

@ -26,15 +26,8 @@
uint8_t PopCnt16[1 << 16];
int SquareDistance[SQUARE_NB][SQUARE_NB];
Bitboard RookMasks [SQUARE_NB];
Bitboard RookMagics [SQUARE_NB];
Bitboard* RookAttacks[SQUARE_NB];
unsigned RookShifts [SQUARE_NB];
Bitboard BishopMasks [SQUARE_NB];
Bitboard BishopMagics [SQUARE_NB];
Bitboard* BishopAttacks[SQUARE_NB];
unsigned BishopShifts [SQUARE_NB];
Magic RookMagics[SQUARE_NB];
Magic BishopMagics[SQUARE_NB];
Bitboard SquareBB[SQUARE_NB];
Bitboard FileBB[FILE_NB];
@ -63,8 +56,7 @@ namespace {
typedef unsigned (Fn)(Square, Bitboard);
void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
Bitboard masks[], unsigned shifts[], Square deltas[], Fn index);
void init_magics(Bitboard table[], Magic magics[], Square deltas[], Fn index);
// 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.
@ -212,8 +204,8 @@ void Bitboards::init() {
Square RookDeltas[] = { NORTH, EAST, SOUTH, WEST };
Square BishopDeltas[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
init_magics(RookTable, RookAttacks, RookMagics, RookMasks, RookShifts, RookDeltas, magic_index<ROOK>);
init_magics(BishopTable, BishopAttacks, BishopMagics, BishopMasks, BishopShifts, BishopDeltas, magic_index<BISHOP>);
init_magics(RookTable, RookMagics, RookDeltas, magic_index<ROOK>);
init_magics(BishopTable, BishopMagics, BishopDeltas, magic_index<BISHOP>);
for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
{
@ -259,8 +251,7 @@ namespace {
// chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we
// use the so called "fancy" approach.
void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
Bitboard masks[], unsigned shifts[], Square deltas[], Fn index) {
void init_magics(Bitboard table[], Magic magics[], Square deltas[], Fn index) {
int seeds[][RANK_NB] = { { 8977, 44560, 54343, 38998, 5731, 95205, 104912, 17020 },
{ 728, 10316, 55013, 32803, 12281, 15100, 16645, 255 } };
@ -269,7 +260,7 @@ namespace {
int age[4096] = {0}, current = 0, i, size;
// attacks[s] is a pointer to the beginning of the attacks table for square 's'
attacks[SQ_A1] = table;
magics[SQ_A1].attacks = table;
for (Square s = SQ_A1; s <= SQ_H8; ++s)
{
@ -281,8 +272,8 @@ namespace {
// all the attacks for each possible subset of the mask and so is 2 power
// the number of 1s of the mask. Hence we deduce the size of the shift to
// apply to the 64 or 32 bits word to get the index.
masks[s] = sliding_attack(deltas, s, 0) & ~edges;
shifts[s] = (Is64Bit ? 64 : 32) - popcount(masks[s]);
magics[s].mask = sliding_attack(deltas, s, 0) & ~edges;
magics[s].shift = (Is64Bit ? 64 : 32) - popcount(magics[s].mask);
// Use Carry-Rippler trick to enumerate all subsets of masks[s] and
// store the corresponding sliding attack bitboard in reference[].
@ -292,16 +283,16 @@ namespace {
reference[size] = sliding_attack(deltas, s, b);
if (HasPext)
attacks[s][pext(b, masks[s])] = reference[size];
magics[s].attacks[pext(b, magics[s].mask)] = reference[size];
size++;
b = (b - masks[s]) & masks[s];
b = (b - magics[s].mask) & magics[s].mask;
} while (b);
// Set the offset for the table of the next square. We have individual
// table sizes for each square with "Fancy Magic Bitboards".
if (s < SQ_H8)
attacks[s + 1] = attacks[s] + size;
magics[s + 1].attacks = magics[s].attacks + size;
if (HasPext)
continue;
@ -312,8 +303,8 @@ namespace {
// until we find the one that passes the verification test.
do {
do
magics[s] = rng.sparse_rand<Bitboard>();
while (popcount((magics[s] * masks[s]) >> 56) < 6);
magics[s].magic = rng.sparse_rand<Bitboard>();
while (popcount((magics[s].magic * magics[s].mask) >> 56) < 6);
// A good magic must map every possible occupancy to an index that
// looks up the correct sliding attack in the attacks[s] database.
@ -326,9 +317,9 @@ namespace {
if (age[idx] < current)
{
age[idx] = current;
attacks[s][idx] = reference[i];
magics[s].attacks[idx] = reference[i];
}
else if (attacks[s][idx] != reference[i])
else if (magics[s].attacks[idx] != reference[i])
break;
}
} while (i < size);

40
src/bitboard.h
View file

@ -209,41 +209,47 @@ template<> inline int distance<File>(Square x, Square y) { return distance(file_
template<> inline int distance<Rank>(Square x, Square y) { return distance(rank_of(x), rank_of(y)); }
/// Magic holds all magic relevant data for a single square
struct Magic {
Bitboard mask;
Bitboard magic;
Bitboard* attacks;
unsigned shift;
};
/// 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.
template<PieceType Pt>
inline unsigned magic_index(Square s, Bitboard occupied) {
extern Bitboard RookMasks[SQUARE_NB];
extern Bitboard RookMagics[SQUARE_NB];
extern unsigned RookShifts[SQUARE_NB];
extern Bitboard BishopMasks[SQUARE_NB];
extern Bitboard BishopMagics[SQUARE_NB];
extern unsigned BishopShifts[SQUARE_NB];
extern Magic RookMagics[SQUARE_NB];
extern Magic BishopMagics[SQUARE_NB];
Bitboard* const Masks = Pt == ROOK ? RookMasks : BishopMasks;
Bitboard* const Magics = Pt == ROOK ? RookMagics : BishopMagics;
unsigned* const Shifts = Pt == ROOK ? RookShifts : BishopShifts;
const Magic* Magics = Pt == ROOK ? RookMagics : BishopMagics;
Bitboard mask = Magics[s].mask;
Bitboard magic = Magics[s].magic;
unsigned shift = Magics[s].shift;
if (HasPext)
return unsigned(pext(occupied, Masks[s]));
return unsigned(pext(occupied, mask));
if (Is64Bit)
return unsigned(((occupied & Masks[s]) * Magics[s]) >> Shifts[s]);
return unsigned(((occupied & mask) * magic) >> shift);
unsigned lo = unsigned(occupied) & unsigned(Masks[s]);
unsigned hi = unsigned(occupied >> 32) & unsigned(Masks[s] >> 32);
return (lo * unsigned(Magics[s]) ^ hi * unsigned(Magics[s] >> 32)) >> Shifts[s];
unsigned lo = unsigned(occupied) & unsigned(mask);
unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
}
template<PieceType Pt>
inline Bitboard attacks_bb(Square s, Bitboard occupied) {
extern Bitboard* RookAttacks[SQUARE_NB];
extern Bitboard* BishopAttacks[SQUARE_NB];
extern Magic RookMagics[SQUARE_NB];
extern Magic BishopMagics[SQUARE_NB];
return (Pt == ROOK ? RookAttacks : BishopAttacks)[s][magic_index<Pt>(s, occupied)];
return (Pt == ROOK ? RookMagics : BishopMagics)[s].attacks[magic_index<Pt>(s, occupied)];
}
inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {