From 22b9307aba0f78aa92abcf85e807af8b64011c7a Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Tue, 1 Nov 2011 09:07:23 +0100 Subject: [PATCH] Further touches to magic bitboards code No functional change. Signed-off-by: Marco Costalba --- src/bitboard.cpp | 73 +++++++++++++++++++++++------------------------- src/bitboard.h | 27 ++++++++++-------- 2 files changed, 51 insertions(+), 49 deletions(-) diff --git a/src/bitboard.cpp b/src/bitboard.cpp index 758796be..b36f8a29 100644 --- a/src/bitboard.cpp +++ b/src/bitboard.cpp @@ -67,8 +67,8 @@ namespace { Bitboard RookTable[0x19000]; // Storage space for rook attacks Bitboard BishopTable[0x1480]; // Storage space for bishop attacks - void init_magic_bitboards(Bitboard* attacks[], Bitboard magics[], - Bitboard masks[], int shifts[], Square deltas[]); + void init_magic_bitboards(PieceType pt, Bitboard* attacks[], Bitboard magics[], + Bitboard masks[], int shifts[]); } @@ -228,14 +228,8 @@ void init_bitboards() { set_bit(&StepAttacksBB[make_piece(c, pt)][s], to); } - Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W }; - Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW }; - - RAttacks[0] = RookTable; - BAttacks[0] = BishopTable; - - init_magic_bitboards(RAttacks, RMagics, RMasks, RShifts, RDeltas); - init_magic_bitboards(BAttacks, BMagics, BMasks, BShifts, BDeltas); + init_magic_bitboards(ROOK, RAttacks, RMagics, RMasks, RShifts); + init_magic_bitboards(BISHOP, BAttacks, BMagics, BMasks, BShifts); for (Square s = SQ_A1; s <= SQ_H8; s++) { @@ -248,35 +242,35 @@ void init_bitboards() { for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++) if (bit_is_set(QueenPseudoAttacks[s1], s2)) { - int f = file_distance(s1, s2); - int r = rank_distance(s1, s2); + Square delta = (s2 - s1) / square_distance(s1, s2); - Square d = (s2 - s1) / std::max(f, r); - - for (Square s3 = s1 + d; s3 != s2; s3 += d) - set_bit(&BetweenBB[s1][s2], s3); + for (Square s = s1 + delta; s != s2; s += delta) + set_bit(&BetweenBB[s1][s2], s); } } namespace { - Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[]) { + Bitboard sliding_attacks(PieceType pt, Square sq, Bitboard occupied) { + Square deltas[][4] = { { DELTA_N, DELTA_E, DELTA_S, DELTA_W }, + { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW } }; Bitboard attacks = 0; + Square* delta = (pt == ROOK ? deltas[0] : deltas[1]); for (int i = 0; i < 4; i++) { - Square s = sq + deltas[i]; + Square s = sq + delta[i]; - while (square_is_ok(s) && square_distance(s, s - deltas[i]) == 1) + while (square_is_ok(s) && square_distance(s, s - delta[i]) == 1) { set_bit(&attacks, s); if (bit_is_set(occupied, s)) break; - s += deltas[i]; + s += delta[i]; } } return attacks; @@ -309,14 +303,17 @@ namespace { // 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[]) { + void init_magic_bitboards(PieceType pt, Bitboard* attacks[], Bitboard magics[], + Bitboard masks[], int shifts[]) { - const int MagicBoosters[][8] = { { 3191, 2184, 1310, 3618, 2091, 1308, 2452, 3996 }, - { 1059, 3608, 605, 3234, 3326, 38, 2029, 3043 } }; + 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], edges, b; - int key, maxKey, index, booster; + int i, size, index, booster; + + // attacks[s] is a pointer to the beginning of the attacks table for square 's' + attacks[SQ_A1] = (pt == ROOK ? RookTable : BishopTable); for (Square s = SQ_A1; s <= SQ_H8; s++) { @@ -328,22 +325,22 @@ 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_attacks(s, EmptyBoardBB, deltas) & ~edges; + masks[s] = sliding_attacks(pt, s, EmptyBoardBB) & ~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; + // store the corresponding sliding attacks bitboard in reference[]. + b = size = 0; do { - occupancy[maxKey] = b; - reference[maxKey++] = sliding_attacks(s, b, deltas); + occupancy[size] = b; + reference[size++] = sliding_attacks(pt, s, b); b = (b - masks[s]) & masks[s]; } 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] + maxKey; + attacks[s + 1] = attacks[s] + size; booster = MagicBoosters[CpuIs64Bit][rank_of(s)]; @@ -351,24 +348,24 @@ namespace { // until we find the one that passes the verification test. do { magics[s] = pick_random(masks[s], rk, booster); - memset(attacks[s], 0, maxKey * sizeof(Bitboard)); + memset(attacks[s], 0, size * 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++) + for (i = 0; i < size; i++) { - index = CpuIs64Bit ? unsigned((occupancy[key] * magics[s]) >> shifts[s]) - : unsigned(occupancy[key] * magics[s] ^ (occupancy[key] >> 32) * (magics[s] >> 32)) >> shifts[s]; + index = (pt == ROOK ? rook_index(s, occupancy[i]) + : bishop_index(s, occupancy[i])); if (!attacks[s][index]) - attacks[s][index] = reference[key]; + attacks[s][index] = reference[i]; - else if (attacks[s][index] != reference[key]) + else if (attacks[s][index] != reference[i]) break; } - } while (key != maxKey); + } while (i != size); } } } diff --git a/src/bitboard.h b/src/bitboard.h index c6136549..09c00597 100644 --- a/src/bitboard.h +++ b/src/bitboard.h @@ -171,30 +171,35 @@ inline Bitboard in_front_bb(Color c, Square s) { #if defined(IS_64BIT) -inline Bitboard rook_attacks_bb(Square s, Bitboard occ) { - return RAttacks[s][((occ & RMasks[s]) * RMagics[s]) >> RShifts[s]]; +FORCE_INLINE unsigned rook_index(Square s, Bitboard occ) { + return unsigned(((occ & RMasks[s]) * RMagics[s]) >> RShifts[s]); } -inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) { - return BAttacks[s][((occ & BMasks[s]) * BMagics[s]) >> BShifts[s]]; +FORCE_INLINE unsigned bishop_index(Square s, Bitboard occ) { + return unsigned(((occ & BMasks[s]) * BMagics[s]) >> BShifts[s]); } #else // if !defined(IS_64BIT) -inline Bitboard rook_attacks_bb(Square s, Bitboard occ) { +FORCE_INLINE unsigned rook_index(Square s, Bitboard occ) { Bitboard b = occ & RMasks[s]; - return RAttacks[s] - [unsigned(int(b) * int(RMagics[s]) ^ int(b >> 32) * int(RMagics[s] >> 32)) >> RShifts[s]]; + return unsigned(int(b) * int(RMagics[s]) ^ int(b >> 32) * int(RMagics[s] >> 32)) >> RShifts[s]; } -inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) { +FORCE_INLINE unsigned bishop_index(Square s, Bitboard occ) { Bitboard b = occ & BMasks[s]; - return BAttacks[s] - [unsigned(int(b) * int(BMagics[s]) ^ int(b >> 32) * int(BMagics[s] >> 32)) >> BShifts[s]]; + return unsigned(int(b) * int(BMagics[s]) ^ int(b >> 32) * int(BMagics[s] >> 32)) >> BShifts[s]; } - #endif +inline Bitboard rook_attacks_bb(Square s, Bitboard occ) { + return RAttacks[s][rook_index(s, occ)]; +} + +inline Bitboard bishop_attacks_bb(Square s, Bitboard occ) { + return BAttacks[s][bishop_index(s, occ)]; +} + inline Bitboard queen_attacks_bb(Square s, Bitboard blockers) { return rook_attacks_bb(s, blockers) | bishop_attacks_bb(s, blockers); } -- 2.39.2