std::string s = "+---+---+---+---+---+---+---+---+\n";

for (Rank r = RANK_8; r >= RANK_1; --r)

{

for (File f = FILE_A; f <= FILE_H; ++f)

s += b & make_square(f, r) ? "| X " : "| ";

s += "| " + std::to_string(1 + r) + "\n+---+---+---+---+---+---+---+---+\n";

}

s += " a b c d e f g h\n";

return s;

for (unsigned i = 0; i < (1 << 16); ++i)

PopCnt16[i] = uint8_t(std::bitset<16>(i).count());

for (Square s = SQ_A1; s <= SQ_H8; ++s)

SquareBB[s] = (1ULL << s);

for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)

for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)

SquareDistance[s1][s2] = std::max(distance<File>(s1, s2), distance<Rank>(s1, s2));

init_magics(ROOK, RookTable, RookMagics);

init_magics(BISHOP, BishopTable, BishopMagics);

for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)

{

PawnAttacks[WHITE][s1] = pawn_attacks_bb<WHITE>(square_bb(s1));

PawnAttacks[BLACK][s1] = pawn_attacks_bb<BLACK>(square_bb(s1));

for (int step : {-9, -8, -7, -1, 1, 7, 8, 9} )

PseudoAttacks[KING][s1] |= safe_destination(s1, step);

for (int step : {-17, -15, -10, -6, 6, 10, 15, 17} )

PseudoAttacks[KNIGHT][s1] |= safe_destination(s1, step);

PseudoAttacks[QUEEN][s1] = PseudoAttacks[BISHOP][s1] = attacks_bb<BISHOP>(s1, 0);

PseudoAttacks[QUEEN][s1] |= PseudoAttacks[ ROOK][s1] = attacks_bb< ROOK>(s1, 0);

for (PieceType pt : { BISHOP, ROOK })

for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)

if (PseudoAttacks[pt][s1] & s2)

LineBB[s1][s2] = (attacks_bb(pt, s1, 0) & attacks_bb(pt, s2, 0)) | s1 | s2;

}

Bitboard attacks = 0;

Direction RookDirections[4] = {NORTH, SOUTH, EAST, WEST};

Direction BishopDirections[4] = {NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST};

for (Direction d : (pt == ROOK ? RookDirections : BishopDirections))

{

Square s = sq;

while(safe_destination(s, d) && !(occupied & s))

attacks |= (s += d);

}

return attacks;

// Optimal PRNG seeds to pick the correct magics in the shortest time

int seeds[][RANK_NB] = { { 8977, 44560, 54343, 38998, 5731, 95205, 104912, 17020 },

{ 728, 10316, 55013, 32803, 12281, 15100, 16645, 255 } };

Bitboard occupancy[4096], reference[4096], edges, b;

int epoch[4096] = {}, cnt = 0, size = 0;

for (Square s = SQ_A1; s <= SQ_H8; ++s)

{

// Board edges are not considered in the relevant occupancies

edges = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s));

// Given a square 's', the mask is the bitboard of sliding attacks from

// 's' computed on an empty board. The index must be big enough to contain

// 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.

Magic& m = magics[s];

m.mask = sliding_attack(pt, s, 0) & ~edges;

m.shift = (Is64Bit ? 64 : 32) - popcount(m.mask);

// Set the offset for the attacks table of the square. We have individual

// table sizes for each square with "Fancy Magic Bitboards".

m.attacks = s == SQ_A1 ? table : magics[s - 1].attacks + size;

// Use Carry-Rippler trick to enumerate all subsets of masks[s] and

// store the corresponding sliding attack bitboard in reference[].

b = size = 0;

do {

occupancy[size] = b;

reference[size] = sliding_attack(pt, s, b);

if (HasPext)

m.attacks[pext(b, m.mask)] = reference[size];

size++;

b = (b - m.mask) & m.mask;

} while (b);

if (HasPext)

continue;

PRNG rng(seeds[Is64Bit][rank_of(s)]);

// Find a magic for square 's' picking up an (almost) random number

// until we find the one that passes the verification test.

for (int i = 0; i < size; )

{

for (m.magic = 0; popcount((m.magic * m.mask) >> 56) < 6; )

m.magic = rng.sparse_rand<Bitboard>();

// A good magic must map every possible occupancy to an index that

// looks up the correct sliding attack in the attacks[s] database.

// Note that we build up the database for square 's' as a side

// effect of verifying the magic. Keep track of the attempt count

// and save it in epoch[], little speed-up trick to avoid resetting

// m.attacks[] after every failed attempt.

for (++cnt, i = 0; i < size; ++i)

{

unsigned idx = m.index(occupancy[i]);

if (epoch[idx] < cnt)

{

epoch[idx] = cnt;

m.attacks[idx] = reference[i];

}

else if (m.attacks[idx] != reference[i])

break;

}

}

}