#include <cstring>
#include <iostream>
+#include <algorithm>
#include "bitboard.h"
#include "bitcount.h"
// Global bitboards definitions with static storage duration are
// automatically set to zero before enter main().
-Bitboard RMask[64];
-Bitboard RMult[64];
+Bitboard RMasks[64];
+Bitboard RMagics[64];
Bitboard* RAttacks[64];
-int RShift[64];
+int RShifts[64];
-Bitboard BMask[64];
-Bitboard BMult[64];
+Bitboard BMasks[64];
+Bitboard BMagics[64];
Bitboard* BAttacks[64];
-int BShift[64];
+int BShifts[64];
Bitboard SetMaskBB[65];
Bitboard ClearMaskBB[65];
Bitboard QueenPseudoAttacks[64];
uint8_t BitCount8Bit[256];
+int SquareDistance[64][64];
namespace {
CACHE_LINE_ALIGNMENT
int BSFTable[64];
- Bitboard RAttacksTable[0x19000];
- Bitboard BAttacksTable[0x1480];
+ Bitboard RookTable[0x19000]; // Storage space for rook attacks
+ Bitboard BishopTable[0x1480]; // Storage space for bishop attacks
- void do_magics(Bitboard magic[], Bitboard* attack[], Bitboard attTabl[],
- Bitboard mask[], int shift[], Square deltas[]);
+ void init_magic_bitboards(Bitboard* attacks[], Bitboard magics[],
+ Bitboard masks[], int shifts[], Square deltas[]);
}
{
std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
for (File f = FILE_A; f <= FILE_H; f++)
- std::cout << "| " << (bit_is_set(b, make_square(f, r)) ? 'X' : ' ') << ' ';
+ std::cout << "| " << (bit_is_set(b, make_square(f, r)) ? "X " : " ");
std::cout << "|\n";
}
void init_bitboards() {
+ for (Bitboard b = 0; b < 256; b++)
+ BitCount8Bit[b] = (uint8_t)count_1s<CNT32_MAX15>(b);
+
+ for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
+ for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
+ SquareDistance[s1][s2] = std::max(file_distance(s1, s2), rank_distance(s1, s2));
+
SquaresByColorBB[DARK] = 0xAA55AA55AA55AA55ULL;
SquaresByColorBB[LIGHT] = ~SquaresByColorBB[DARK];
for (Square s = SQ_A1; s <= SQ_H8; s++)
{
- SetMaskBB[s] = (1ULL << s);
+ SetMaskBB[s] = 1ULL << s;
ClearMaskBB[s] = ~SetMaskBB[s];
}
AttackSpanMask[c][s] = in_front_bb(c, s) & neighboring_files_bb(s);
}
- for (Bitboard b = 0; b < 256; b++)
- BitCount8Bit[b] = (uint8_t)count_1s<CNT32>(b);
-
- for (int i = 1; i < 64; i++)
+ for (int i = 0; i < 64; i++)
if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems
{
Bitboard b = 1ULL << i;
else
BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i;
- int steps[][9] = {
- {0}, {7,9,0}, {17,15,10,6,-6,-10,-15,-17,0}, {0}, {0}, {0}, {9,7,-7,-9,8,1,-1,-8,0}
- };
+ int steps[][9] = { {}, { 7, 9 }, { 17, 15, 10, 6, -6, -10, -15, -17 },
+ {}, {}, {}, { 9, 7, -7, -9, 8, 1, -1, -8 } };
for (Color c = WHITE; c <= BLACK; c++)
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- for (PieceType pt = PAWN; pt <= KING; pt++)
+ for (PieceType pt = PAWN; pt <= KING; pt++)
+ for (Square s = SQ_A1; s <= SQ_H8; s++)
for (int k = 0; steps[pt][k]; k++)
{
Square to = s + Square(c == WHITE ? steps[pt][k] : -steps[pt][k]);
Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W };
Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
- do_magics(BMult, BAttacks, BAttacksTable, BMask, BShift, BDeltas);
- do_magics(RMult, RAttacks, RAttacksTable, RMask, RShift, RDeltas);
+ RAttacks[0] = RookTable;
+ BAttacks[0] = BishopTable;
+
+ init_magic_bitboards(RAttacks, RMagics, RMasks, RShifts, RDeltas);
+ init_magic_bitboards(BAttacks, BMagics, BMasks, BShifts, BDeltas);
for (Square s = SQ_A1; s <= SQ_H8; s++)
{
int f = file_distance(s1, s2);
int r = rank_distance(s1, s2);
- Square d = (s2 - s1) / Max(f, r);
+ Square d = (s2 - s1) / std::max(f, r);
for (Square s3 = s1 + d; s3 != s2; s3 += d)
set_bit(&BetweenBB[s1][s2], s3);
namespace {
- Bitboard submask(Bitboard mask, int key) {
-
- Bitboard subMask = 0;
- int bitNum = -1;
-
- // Extract an unique submask out of a mask according to the given key
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- if (bit_is_set(mask, s) && bit_is_set(key, Square(++bitNum)))
- set_bit(&subMask, s);
-
- return subMask;
- }
-
- Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[], Bitboard excluded) {
+ Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[]) {
Bitboard attacks = 0;
{
Square s = sq + deltas[i];
- while ( square_is_ok(s)
- && square_distance(s, s - deltas[i]) == 1
- && !bit_is_set(excluded, s))
+ while (square_is_ok(s) && square_distance(s, s - deltas[i]) == 1)
{
set_bit(&attacks, s);
return attacks;
}
- template<bool Is64>
- Bitboard pick_magic(Bitboard mask, RKISS& rk, int booster) {
+ Bitboard pick_random(Bitboard mask, RKISS& rk, int booster) {
Bitboard magic;
- int lsb;
-
- if (!Is64)
- lsb = first_1(mask);
- // Advance PRNG state of a quantity known to be the optimal to
- // quickly retrieve all the magics.
- for (int i = 0; i < booster; i++)
- rk.rand<Bitboard>();
+ // Values s1 and s2 are used to rotate the candidate magic of a
+ // quantity known to be the optimal to quickly find the magics.
+ int s1 = booster & 63, s2 = (booster >> 6) & 63;
while (true)
{
- magic = rk.rand<Bitboard>() & rk.rand<Bitboard>();
- magic &= Is64 ? rk.rand<Bitboard>() : (rk.rand<Bitboard>() | rk.rand<Bitboard>());
+ magic = rk.rand<Bitboard>();
+ magic = (magic >> s1) | (magic << (64 - s1));
+ magic &= rk.rand<Bitboard>();
+ magic = (magic >> s2) | (magic << (64 - s2));
+ magic &= rk.rand<Bitboard>();
- if ( BitCount8Bit[(mask * magic) >> 56] >= 6
- && (Is64 || BitCount8Bit[(lsb * magic) >> 56]))
+ if (BitCount8Bit[(mask * magic) >> 56] >= 6)
return magic;
}
}
- void do_magics(Bitboard magic[], Bitboard* attack[], Bitboard attTabl[],
- Bitboard mask[], int shift[], Square deltas[]) {
- const int MagicBoosters32[] = { 43, 53, 76, 17, 51, 65, 55, 23 };
- const int MagicBoosters64[] = { 26, 21, 21, 32, 31, 9, 5, 11 };
+ // init_magic_bitboards() computes all rook and bishop magics at startup.
+ // Magic bitboards are used to look up attacks of sliding pieces. As reference
+ // see chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we
+ // use the so called "fancy" approach.
+
+ void init_magic_bitboards(Bitboard* attacks[], Bitboard magics[],
+ Bitboard masks[], int shifts[], Square deltas[]) {
+ const int MagicBoosters[][8] = { { 3191, 2184, 1310, 3618, 2091, 1308, 2452, 3996 },
+ { 1059, 3608, 605, 3234, 3326, 38, 2029, 3043 } };
RKISS rk;
- Bitboard occupancy[4096], proofs[4096], excluded;
- int key, maxKey, index, booster, offset = 0;
+ Bitboard occupancy[4096], reference[4096], edges, b;
+ int key, maxKey, index, booster;
for (Square s = SQ_A1; s <= SQ_H8; s++)
{
- excluded = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(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.
+ masks[s] = sliding_attacks(s, EmptyBoardBB, deltas) & ~edges;
+ shifts[s] = (CpuIs64Bit ? 64 : 32) - count_1s<CNT32_MAX15>(masks[s]);
+
+ // Use Carry-Rippler trick to enumerate all subsets of masks[s] and
+ // store the corresponding sliding attacks in reference[].
+ b = maxKey = 0;
+ do {
+ occupancy[maxKey] = b;
+ reference[maxKey++] = sliding_attacks(s, b, deltas);
+ b = (b - masks[s]) & masks[s];
+ } while (b);
- attack[s] = &attTabl[offset];
- mask[s] = sliding_attacks(s, EmptyBoardBB, deltas, excluded);
- shift[s] = (CpuIs64Bit ? 64 : 32) - count_1s<CNT64>(mask[s]);
+ // 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] + maxKey;
- maxKey = 1 << count_1s<CNT32>(mask[s]);
- booster = CpuIs64Bit ? MagicBoosters64[square_rank(s)] : MagicBoosters32[square_rank(s)];
+ booster = MagicBoosters[CpuIs64Bit][rank_of(s)];
- // First compute occupancy and attacks for square 's'
- for (key = 0; key < maxKey; key++)
- {
- occupancy[key] = submask(mask[s], key);
- proofs[key] = sliding_attacks(s, occupancy[key], deltas, EmptyBoardBB);
- }
-
- // Then find a possible magic and corresponding attacks
+ // Find a magic for square 's' picking up an (almost) random number
+ // until we find the one that passes the verification test.
do {
- magic[s] = pick_magic<CpuIs64Bit>(mask[s], rk, booster);
- memset(attack[s], 0, maxKey * sizeof(Bitboard));
+ magics[s] = pick_random(masks[s], rk, booster);
+ memset(attacks[s], 0, maxKey * sizeof(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.
for (key = 0; key < maxKey; key++)
{
- index = CpuIs64Bit ? unsigned((occupancy[key] * magic[s]) >> shift[s])
- : unsigned(occupancy[key] * magic[s] ^ (occupancy[key] >> 32) * (magic[s] >> 32)) >> shift[s];
+ index = CpuIs64Bit ? unsigned((occupancy[key] * magics[s]) >> shifts[s])
+ : unsigned(occupancy[key] * magics[s] ^ (occupancy[key] >> 32) * (magics[s] >> 32)) >> shifts[s];
- if (!attack[s][index])
- attack[s][index] = proofs[key];
+ if (!attacks[s][index])
+ attacks[s][index] = reference[key];
- else if (attack[s][index] != proofs[key])
+ else if (attacks[s][index] != reference[key])
break;
}
} while (key != maxKey);
-
- offset += maxKey;
}
}
}
projects / stockfish / blobdiff