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Reformat pick_random() in magics calculation

Browse source 
No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2012-06-10 11:11:28 +01:00
parent 764d3f44b6
commit 0446fc85de
1 changed files with 13 additions and 17 deletions
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30
src/bitboard.cpp
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@ -50,7 +50,6 @@ Bitboard PassedPawnMask[2][64];
Bitboard AttackSpanMask[2][64]; Bitboard AttackSpanMask[2][64];
Bitboard PseudoAttacks[6][64]; Bitboard PseudoAttacks[6][64];
uint8_t BitCount8Bit[256];
int SquareDistance[64][64]; int SquareDistance[64][64];
namespace { namespace {
@ -61,6 +60,7 @@ namespace {
int MS1BTable[256]; int MS1BTable[256];
Bitboard RTable[0x19000]; // Storage space for rook attacks Bitboard RTable[0x19000]; // Storage space for rook attacks
Bitboard BTable[0x1480]; // Storage space for bishop attacks Bitboard BTable[0x1480]; // Storage space for bishop attacks
uint8_t BitCount8Bit[256];
typedef unsigned (Fn)(Square, Bitboard); typedef unsigned (Fn)(Square, Bitboard);
@ -142,7 +142,7 @@ void Bitboards::print(Bitboard b) {
std::cout << "+---+---+---+---+---+---+---+---+" << '\n'; std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
for (File file = FILE_A; file <= FILE_H; file++) for (File file = FILE_A; file <= FILE_H; file++)
std::cout << "| " << ((b & make_square(file, rank)) ? "X " : " "); std::cout << "| " << (b & make_square(file, rank) ? "X " : " ");
std::cout << "|\n"; std::cout << "|\n";
} }
@ -265,25 +265,17 @@ namespace {
} }
Bitboard pick_random(Bitboard mask, RKISS& rk, int booster) { Bitboard pick_random(RKISS& rk, int booster) {
Bitboard magic;
// Values s1 and s2 are used to rotate the candidate magic of a // Values s1 and s2 are used to rotate the candidate magic of a
// quantity known to be the optimal to quickly find the magics. // quantity known to be the optimal to quickly find the magics.
int s1 = booster & 63, s2 = (booster >> 6) & 63; int s1 = booster & 63, s2 = (booster >> 6) & 63;
while (true) Bitboard m = rk.rand<Bitboard>();
{ m = (m >> s1) | (m << (64 - s1));
magic = rk.rand<Bitboard>(); m &= rk.rand<Bitboard>();
magic = (magic >> s1) | (magic << (64 - s1)); m = (m >> s2) | (m << (64 - s2));
magic &= rk.rand<Bitboard>(); return m & rk.rand<Bitboard>();
magic = (magic >> s2) | (magic << (64 - s2));
magic &= rk.rand<Bitboard>();
if (BitCount8Bit[(mask * magic) >> 56] >= 6)
return magic;
}
} }
@ -336,7 +328,9 @@ namespace {
// Find a magic for square 's' picking up an (almost) random number // Find a magic for square 's' picking up an (almost) random number
// until we find the one that passes the verification test. // until we find the one that passes the verification test.
do { do {
magics[s] = pick_random(masks[s], rk, booster); do magics[s] = pick_random(rk, booster);
while (BitCount8Bit[(magics[s] * masks[s]) >> 56] < 6);
memset(attacks[s], 0, size * sizeof(Bitboard)); memset(attacks[s], 0, size * sizeof(Bitboard));
// A good magic must map every possible occupancy to an index that // A good magic must map every possible occupancy to an index that
@ -350,6 +344,8 @@ namespace {
if (attack && attack != reference[i]) if (attack && attack != reference[i])
break; break;
assert(reference[i] != 0);
attack = reference[i]; attack = reference[i];
} }
} while (i != size); } while (i != size);