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Move Attacks out of Bitboard File
Over the past few months our attacks and bitboard logic got a bit more involved and target specific, so I think it makes sense to split this up a bit more into separate files. While it's not in an ideal state I think it's first step and can be improved later, `pawn_attacks_bb` could also be moved into the attacks.h but this was more of an oversight from my side. closes https://github.com/official-stockfish/Stockfish/pull/6833 No functional change
This commit is contained in:
Disservin
committed by
Joost VandeVondele
Joost VandeVondele
parent
be9df38f27
commit
24d6398490
+239
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/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2026 The Stockfish developers (see AUTHORS file)
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "attacks.h"
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#include <array>
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#include "misc.h"
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namespace Stockfish::Attacks {
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namespace {
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Bitboard LineBB[SQUARE_NB][SQUARE_NB];
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Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
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Bitboard RayPassBB[SQUARE_NB][SQUARE_NB];
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alignas(64) Magic Magics[SQUARE_NB][2];
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}
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#ifdef USE_PEXT
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using MagicMask = uint16_t;
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#else
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using MagicMask = Bitboard;
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#endif
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#ifdef USE_HYPERBOLA_QUINT
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static Bitboard line_mask(Square sq, Direction d1, Direction d2) {
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Bitboard mask = 0, dest;
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for (Direction d : {d1, d2})
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{
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Square s = sq;
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while ((dest = safe_destination(s, d)))
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{
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mask |= dest;
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s += d;
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}
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}
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return mask;
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}
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static void init_magics(Magic magics[][2]) {
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for (Square s = SQ_A1; s <= SQ_H8; ++s)
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{
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Magic& rook = magics[s][ROOK - BISHOP];
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rook.mask1 = line_mask(s, NORTH, SOUTH);
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rook.mask2 = line_mask(s, EAST, WEST);
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Magic& bishop = magics[s][BISHOP - BISHOP];
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bishop.mask1 = line_mask(s, NORTH_EAST, SOUTH_WEST);
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bishop.mask2 = line_mask(s, NORTH_WEST, SOUTH_EAST);
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rook.r = bishop.r = square_bb(s) * 2;
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rook.rr = bishop.rr = square_bb(Square(63 - int(s))) * 2;
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}
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}
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#else
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namespace {
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[[maybe_unused]] constexpr Bitboard constexpr_pext(Bitboard b, Bitboard m) {
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Bitboard result = 0, bit = 0;
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while (m)
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{
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Bitboard last = m & -m;
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result |= bool(b & last) << bit++;
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m ^= last;
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}
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return result;
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}
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#ifdef USE_COMPTIME_ATTACKS
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constexpr
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#endif
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void
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init_magics(PieceType pt,
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MagicMask table[],
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Magic magics[][2],
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[[maybe_unused]] bool tableAlreadyInit) {
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#if !defined(USE_COMPTIME_ATTACKS)
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tableAlreadyInit = false;
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#endif
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#ifndef USE_PEXT
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int seeds[][RANK_NB] = {{8977, 44560, 54343, 38998, 5731, 95205, 104912, 17020},
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{728, 10316, 55013, 32803, 12281, 15100, 16645, 255}};
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Bitboard occupancy[4096];
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int epoch[4096] = {}, cnt = 0;
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Bitboard reference[4096] = {};
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#endif
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int size = 0;
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for (Square s = SQ_A1; s <= SQ_H8; ++s)
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{
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Bitboard edges = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s));
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Magic& m = magics[s][pt - BISHOP];
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Bitboard attacks = sliding_attack(pt, s, 0);
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m.mask = attacks & ~edges;
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#ifdef USE_PEXT
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m.pseudoAttacks = attacks;
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#else
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m.shift = (Is64Bit ? 64 : 32) - popcount(m.mask);
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#endif
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m.attacks = s == SQ_A1 ? table : magics[s - 1][pt - BISHOP].attacks + size;
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size = 0;
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Bitboard b = 0;
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[[maybe_unused]] Bitboard prevSliding = -1;
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do
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{
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#ifdef USE_PEXT
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if (!tableAlreadyInit)
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{
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Bitboard sliding = sliding_attack(pt, s, b);
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m.attacks[size] =
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sliding != prevSliding ? constexpr_pext(sliding, attacks) : m.attacks[size - 1];
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prevSliding = sliding;
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}
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#else
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occupancy[size] = b;
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reference[size] = sliding_attack(pt, s, b);
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#endif
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size++;
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b = (b - m.mask) & m.mask;
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} while (b);
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#ifndef USE_PEXT
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PRNG rng(seeds[Is64Bit][rank_of(s)]);
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for (int i = 0; i < size;)
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{
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for (m.magic = 0; popcount((m.magic * m.mask) >> 56) < 6;)
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m.magic = rng.sparse_rand<Bitboard>();
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for (++cnt, i = 0; i < size; ++i)
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{
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unsigned idx = m.index(occupancy[i]);
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if (epoch[idx] < cnt)
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{
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epoch[idx] = cnt;
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m.attacks[idx] = reference[i];
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}
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else if (m.attacks[idx] != reference[i])
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break;
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}
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}
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#endif
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}
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}
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#if defined(USE_COMPTIME_ATTACKS) && defined(USE_PEXT)
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constexpr auto RookTable = []() {
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std::array<uint16_t, 0x19000> result{};
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Magic magics[64][2] = {};
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init_magics(ROOK, result.data(), magics, false);
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return result;
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}();
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constexpr auto BishopTable = []() {
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std::array<uint16_t, 0x1480> result{};
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Magic magics[64][2] = {};
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init_magics(BISHOP, result.data(), magics, false);
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return result;
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}();
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#else
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std::array<MagicMask, 0x19000> RookTable;
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std::array<MagicMask, 0x1480> BishopTable;
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#endif
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}
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#endif
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void init() {
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#ifdef USE_HYPERBOLA_QUINT
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init_magics(Magics);
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#else
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init_magics(ROOK, const_cast<MagicMask*>(RookTable.data()), Magics, true);
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init_magics(BISHOP, const_cast<MagicMask*>(BishopTable.data()), Magics, true);
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#endif
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for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
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{
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for (PieceType pt : {BISHOP, ROOK})
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for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
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{
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if (PseudoAttacks[pt][s1] & s2)
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{
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LineBB[s1][s2] = (attacks_bb(pt, s1, 0) & attacks_bb(pt, s2, 0)) | s1 | s2;
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BetweenBB[s1][s2] =
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(attacks_bb(pt, s1, square_bb(s2)) & attacks_bb(pt, s2, square_bb(s1)));
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RayPassBB[s1][s2] =
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attacks_bb(pt, s1, 0) & (attacks_bb(pt, s2, square_bb(s1)) | s2);
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}
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BetweenBB[s1][s2] |= s2;
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}
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}
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}
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const Magic& magic(Square s, PieceType pt) {
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assert((pt == BISHOP || pt == ROOK) && is_ok(s));
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return Magics[s][pt - BISHOP];
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}
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Bitboard line_bb(Square s1, Square s2) {
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assert(is_ok(s1) && is_ok(s2));
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return LineBB[s1][s2];
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}
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Bitboard between_bb(Square s1, Square s2) {
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assert(is_ok(s1) && is_ok(s2));
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return BetweenBB[s1][s2];
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}
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Bitboard ray_pass_bb(Square s1, Square s2) {
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assert(is_ok(s1) && is_ok(s2));
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return RayPassBB[s1][s2];
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}
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} // namespace Stockfish::Attacks
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