X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=758796bed0bf4ac0122174ca0cad1a065b9852bb;hp=2fd0cadaaadf86c1cdd463c4dd8cb33f3275e97d;hb=90890844ade67d8081a5284700cc2ef3ebdbb62d;hpb=b3a0b389d279dacd70fea429088122d02362d14a diff --git a/src/bitboard.cpp b/src/bitboard.cpp index 2fd0cada..758796be 100644 --- a/src/bitboard.cpp +++ b/src/bitboard.cpp @@ -19,6 +19,7 @@ #include #include +#include #include "bitboard.h" #include "bitcount.h" @@ -26,15 +27,15 @@ // 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]; @@ -56,17 +57,18 @@ Bitboard RookPseudoAttacks[64]; 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 init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[], - Bitboard mask[], int shift[], Square delta[]); + void init_magic_bitboards(Bitboard* attacks[], Bitboard magics[], + Bitboard masks[], int shifts[], Square deltas[]); } @@ -154,6 +156,13 @@ Square pop_1st_bit(Bitboard* bb) { void init_bitboards() { + for (Bitboard b = 0; b < 256; b++) + BitCount8Bit[b] = (uint8_t)count_1s(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]; @@ -194,9 +203,6 @@ void init_bitboards() { 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(b); - for (int i = 0; i < 64; i++) if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems { @@ -222,11 +228,14 @@ void init_bitboards() { set_bit(&StepAttacksBB[make_piece(c, pt)][s], to); } - Square RDelta[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W }; - Square BDelta[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW }; + Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W }; + Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW }; - init_sliding_attacks(BMult, BAttacks, BAttacksTable, BMask, BShift, BDelta); - init_sliding_attacks(RMult, RAttacks, RAttacksTable, RMask, RShift, RDelta); + 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++) { @@ -242,7 +251,7 @@ void init_bitboards() { 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); @@ -252,49 +261,28 @@ void init_bitboards() { namespace { - Bitboard submask(Bitboard mask, int key) { - - Bitboard b, subMask = 0; - int bitProbe = 1; - - // Extract an unique submask out of a mask according to the given key - while (mask) - { - b = mask & -mask; - mask ^= b; - - if (key & bitProbe) - subMask |= b; - - bitProbe <<= 1; - } - return subMask; - } - - Bitboard sliding_attacks(Square sq, Bitboard occupied, Square delta[], Bitboard excluded) { + Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[]) { Bitboard attacks = 0; for (int i = 0; i < 4; i++) { - Square s = sq + delta[i]; + Square s = sq + deltas[i]; - while ( square_is_ok(s) - && square_distance(s, s - delta[i]) == 1 - && !bit_is_set(excluded, s)) + while (square_is_ok(s) && square_distance(s, s - deltas[i]) == 1) { set_bit(&attacks, s); if (bit_is_set(occupied, s)) break; - s += delta[i]; + s += deltas[i]; } } return attacks; } - Bitboard pick_magic(Bitboard mask, RKISS& rk, int booster) { + Bitboard pick_random(Bitboard mask, RKISS& rk, int booster) { Bitboard magic; @@ -315,48 +303,69 @@ namespace { } } - void init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[], - Bitboard mask[], int shift[], Square delta[]) { + + // 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], reference[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)); - - attack[s] = &attTable[offset]; - mask[s] = sliding_attacks(s, EmptyBoardBB, delta, excluded); - shift[s] = (CpuIs64Bit ? 64 : 32) - count_1s(mask[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(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); - maxKey = 1 << count_1s(mask[s]); - offset += maxKey; - booster = MagicBoosters[CpuIs64Bit][square_rank(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; - // First compute occupancy and attacks for square 's' - for (key = 0; key < maxKey; key++) - { - occupancy[key] = submask(mask[s], key); - reference[key] = sliding_attacks(s, occupancy[key], delta, EmptyBoardBB); - } + booster = MagicBoosters[CpuIs64Bit][rank_of(s)]; - // Then find a possible magic and the 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(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] = reference[key]; + if (!attacks[s][index]) + attacks[s][index] = reference[key]; - else if (attack[s][index] != reference[key]) + else if (attacks[s][index] != reference[key]) break; } } while (key != maxKey);