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543 lines
18 KiB
C++
543 lines
18 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
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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 <cassert>
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#include "bitcount.h"
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#include "movegen.h"
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// Simple macro to wrap a very common while loop, no facny, no flexibility,
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// hardcoded list name 'mlist' and from square 'from'.
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#define SERIALIZE_MOVES(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
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// Version used for pawns, where the 'from' square is given as a delta from the 'to' square
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#define SERIALIZE_MOVES_D(b, d) while (b) { to = pop_1st_bit(&b); (*mlist++).move = make_move(to + (d), to); }
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namespace {
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enum CastlingSide {
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KING_SIDE,
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QUEEN_SIDE
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};
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template<CastlingSide>
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MoveStack* generate_castle_moves(const Position&, MoveStack*, Color us);
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template<Color, MoveType>
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MoveStack* generate_pawn_moves(const Position&, MoveStack*, Bitboard, Square);
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template<PieceType Pt>
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inline MoveStack* generate_discovered_checks(const Position& pos, MoveStack* mlist, Square from) {
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assert(Pt != QUEEN);
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Bitboard b = pos.attacks_from<Pt>(from) & pos.empty_squares();
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if (Pt == KING)
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{
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Square ksq = pos.king_square(opposite_color(pos.side_to_move()));
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b &= ~QueenPseudoAttacks[ksq];
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}
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SERIALIZE_MOVES(b);
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return mlist;
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}
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template<PieceType Pt>
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inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
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Bitboard dc, Square ksq) {
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assert(Pt != KING);
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Bitboard checkSqs, b;
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Square from;
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const Square* ptr = pos.piece_list_begin(us, Pt);
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if ((from = *ptr++) == SQ_NONE)
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return mlist;
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checkSqs = pos.attacks_from<Pt>(ksq) & pos.empty_squares();
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do
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{
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if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
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|| (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
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|| (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
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continue;
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if (dc && bit_is_set(dc, from))
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continue;
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b = pos.attacks_from<Pt>(from) & checkSqs;
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SERIALIZE_MOVES(b);
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} while ((from = *ptr++) != SQ_NONE);
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return mlist;
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}
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template<>
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FORCE_INLINE MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
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return (us == WHITE ? generate_pawn_moves<WHITE, MV_CHECK>(p, m, dc, ksq)
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: generate_pawn_moves<BLACK, MV_CHECK>(p, m, dc, ksq));
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}
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template<PieceType Pt, MoveType Type>
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FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
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assert(Pt == PAWN);
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assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_EVASION);
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return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
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: generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE));
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}
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template<PieceType Pt>
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FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
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Bitboard b;
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Square from;
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const Square* ptr = pos.piece_list_begin(us, Pt);
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if (*ptr != SQ_NONE)
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{
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do {
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from = *ptr;
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b = pos.attacks_from<Pt>(from) & target;
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SERIALIZE_MOVES(b);
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} while (*++ptr != SQ_NONE);
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}
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return mlist;
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}
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template<>
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FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
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Bitboard b;
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Square from = pos.king_square(us);
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b = pos.attacks_from<KING>(from) & target;
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SERIALIZE_MOVES(b);
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return mlist;
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}
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}
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/// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
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/// promotions. Returns a pointer to the end of the move list.
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///
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/// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
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/// underpromotions. Returns a pointer to the end of the move list.
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///
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/// generate<MV_NON_EVASION> generates all pseudo-legal captures and
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/// non-captures. Returns a pointer to the end of the move list.
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template<MoveType Type>
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MoveStack* generate(const Position& pos, MoveStack* mlist) {
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assert(pos.is_ok());
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assert(!pos.in_check());
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Color us = pos.side_to_move();
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Bitboard target;
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if (Type == MV_CAPTURE || Type == MV_NON_EVASION)
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target = pos.pieces_of_color(opposite_color(us));
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else if (Type == MV_NON_CAPTURE)
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target = pos.empty_squares();
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else
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assert(false);
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if (Type == MV_NON_EVASION)
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{
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mlist = generate_piece_moves<PAWN, MV_CAPTURE>(pos, mlist, us, target);
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mlist = generate_piece_moves<PAWN, MV_NON_CAPTURE>(pos, mlist, us, pos.empty_squares());
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target |= pos.empty_squares();
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}
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else
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mlist = generate_piece_moves<PAWN, Type>(pos, mlist, us, target);
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mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
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mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
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mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
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mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
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mlist = generate_piece_moves<KING>(pos, mlist, us, target);
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if (Type != MV_CAPTURE)
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{
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if (pos.can_castle_kingside(us))
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mlist = generate_castle_moves<KING_SIDE>(pos, mlist, us);
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if (pos.can_castle_queenside(us))
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mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist, us);
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}
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return mlist;
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}
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// Explicit template instantiations
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template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
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template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
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template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
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/// generate_non_capture_checks() generates all pseudo-legal non-captures and knight
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/// underpromotions that give check. Returns a pointer to the end of the move list.
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template<>
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MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
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assert(pos.is_ok());
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assert(!pos.in_check());
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Bitboard b, dc;
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Square from;
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Color us = pos.side_to_move();
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Square ksq = pos.king_square(opposite_color(us));
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assert(pos.piece_on(ksq) == make_piece(opposite_color(us), KING));
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// Discovered non-capture checks
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b = dc = pos.discovered_check_candidates(us);
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while (b)
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{
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from = pop_1st_bit(&b);
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switch (pos.type_of_piece_on(from))
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{
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case PAWN: /* Will be generated togheter with pawns direct checks */ break;
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case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, mlist, from); break;
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case BISHOP: mlist = generate_discovered_checks<BISHOP>(pos, mlist, from); break;
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case ROOK: mlist = generate_discovered_checks<ROOK>(pos, mlist, from); break;
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case KING: mlist = generate_discovered_checks<KING>(pos, mlist, from); break;
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default: assert(false); break;
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}
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}
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// Direct non-capture checks
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mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
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mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
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mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
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mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
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return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
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}
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/// generate_evasions() generates all pseudo-legal check evasions when
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/// the side to move is in check. Returns a pointer to the end of the move list.
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template<>
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MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
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assert(pos.is_ok());
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assert(pos.in_check());
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Bitboard b, target;
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Square from, checksq;
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int checkersCnt = 0;
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Color us = pos.side_to_move();
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Square ksq = pos.king_square(us);
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Bitboard checkers = pos.checkers();
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Bitboard sliderAttacks = EmptyBoardBB;
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assert(pos.piece_on(ksq) == make_piece(us, KING));
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assert(checkers);
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// Find squares attacked by slider checkers, we will remove
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// them from the king evasions set so to early skip known
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// illegal moves and avoid an useless legality check later.
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b = checkers;
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do
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{
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checkersCnt++;
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checksq = pop_1st_bit(&b);
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assert(pos.color_of_piece_on(checksq) == opposite_color(us));
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switch (pos.type_of_piece_on(checksq))
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{
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case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
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case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
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case QUEEN:
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// In case of a queen remove also squares attacked in the other direction to
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// avoid possible illegal moves when queen and king are on adjacent squares.
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if (RookPseudoAttacks[checksq] & (1ULL << ksq))
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sliderAttacks |= RookPseudoAttacks[checksq] | pos.attacks_from<BISHOP>(checksq);
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else
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sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
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default:
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break;
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}
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} while (b);
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// Generate evasions for king, capture and non capture moves
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b = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
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from = ksq;
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SERIALIZE_MOVES(b);
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// Generate evasions for other pieces only if not double check
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if (checkersCnt > 1)
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return mlist;
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// Find squares where a blocking evasion or a capture of the
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// checker piece is possible.
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target = squares_between(checksq, ksq) | checkers;
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mlist = generate_piece_moves<PAWN, MV_EVASION>(pos, mlist, us, target);
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mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
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mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
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mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
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return generate_piece_moves<QUEEN>(pos, mlist, us, target);
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}
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/// generate<MV_LEGAL / MV_PSEUDO_LEGAL> computes a complete list of legal
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/// or pseudo-legal moves in the current position.
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template<>
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MoveStack* generate<MV_PSEUDO_LEGAL>(const Position& pos, MoveStack* mlist) {
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assert(pos.is_ok());
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return pos.in_check() ? generate<MV_EVASION>(pos, mlist)
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: generate<MV_NON_EVASION>(pos, mlist);
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}
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template<>
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MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
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assert(pos.is_ok());
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MoveStack *last, *cur = mlist;
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Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
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last = generate<MV_PSEUDO_LEGAL>(pos, mlist);
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// Remove illegal moves from the list
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while (cur != last)
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if (!pos.pl_move_is_legal(cur->move, pinned))
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cur->move = (--last)->move;
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else
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cur++;
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return last;
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}
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namespace {
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template<Square Delta>
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inline Bitboard move_pawns(Bitboard p) {
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return Delta == DELTA_N ? p << 8 : Delta == DELTA_S ? p >> 8 :
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Delta == DELTA_NE ? p << 9 : Delta == DELTA_SE ? p >> 7 :
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Delta == DELTA_NW ? p << 7 : Delta == DELTA_SW ? p >> 9 : p;
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}
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template<MoveType Type, Square Delta>
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inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard target) {
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const Bitboard TFileABB = (Delta == DELTA_NE || Delta == DELTA_SE ? FileABB : FileHBB);
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Bitboard b;
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Square to;
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// Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
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b = move_pawns<Delta>(pawns) & target & ~TFileABB;
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SERIALIZE_MOVES_D(b, -Delta);
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return mlist;
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}
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template<Color Us, MoveType Type, Square Delta>
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inline MoveStack* generate_promotions(const Position& pos, MoveStack* mlist, Bitboard pawnsOn7, Bitboard target) {
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const Bitboard TFileABB = (Delta == DELTA_NE || Delta == DELTA_SE ? FileABB : FileHBB);
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Bitboard b;
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Square to;
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// Promotions and under-promotions, both captures and non-captures
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b = move_pawns<Delta>(pawnsOn7) & target;
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if (Delta != DELTA_N && Delta != DELTA_S)
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b &= ~TFileABB;
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while (b)
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{
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to = pop_1st_bit(&b);
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if (Type == MV_CAPTURE || Type == MV_EVASION)
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(*mlist++).move = make_promotion_move(to - Delta, to, QUEEN);
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if (Type == MV_NON_CAPTURE || Type == MV_EVASION)
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{
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(*mlist++).move = make_promotion_move(to - Delta, to, ROOK);
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(*mlist++).move = make_promotion_move(to - Delta, to, BISHOP);
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(*mlist++).move = make_promotion_move(to - Delta, to, KNIGHT);
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}
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// This is the only possible under promotion that can give a check
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// not already included in the queen-promotion.
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if ( Type == MV_CHECK
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&& bit_is_set(pos.attacks_from<KNIGHT>(to), pos.king_square(opposite_color(Us))))
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(*mlist++).move = make_promotion_move(to - Delta, to, KNIGHT);
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else (void)pos; // Silence a warning under MSVC
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}
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return mlist;
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}
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template<Color Us, MoveType Type>
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MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
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// Calculate our parametrized parameters at compile time, named
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// according to the point of view of white side.
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
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const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
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const Square TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
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const Square TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
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const Square TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
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Square to;
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Bitboard b1, b2, dc1, dc2, pawnPushes, emptySquares;
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Bitboard pawns = pos.pieces(PAWN, Us);
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Bitboard pawnsOn7 = pawns & TRank7BB;
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Bitboard enemyPieces = (Type == MV_CAPTURE ? target : pos.pieces_of_color(Them));
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// Pre-calculate pawn pushes before changing emptySquares definition
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if (Type != MV_CAPTURE)
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{
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emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
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pawnPushes = move_pawns<TDELTA_N>(pawns & ~TRank7BB) & emptySquares;
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}
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if (Type == MV_EVASION)
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{
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emptySquares &= target; // Only blocking squares
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enemyPieces &= target; // Capture only the checker piece
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}
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// Promotions and underpromotions
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if (pawnsOn7)
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{
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if (Type == MV_CAPTURE)
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emptySquares = pos.empty_squares();
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pawns &= ~TRank7BB;
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mlist = generate_promotions<Us, Type, TDELTA_NE>(pos, mlist, pawnsOn7, enemyPieces);
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mlist = generate_promotions<Us, Type, TDELTA_NW>(pos, mlist, pawnsOn7, enemyPieces);
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mlist = generate_promotions<Us, Type, TDELTA_N >(pos, mlist, pawnsOn7, emptySquares);
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}
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// Standard captures
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if (Type == MV_CAPTURE || Type == MV_EVASION)
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{
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mlist = generate_pawn_captures<Type, TDELTA_NE>(mlist, pawns, enemyPieces);
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mlist = generate_pawn_captures<Type, TDELTA_NW>(mlist, pawns, enemyPieces);
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}
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// Single and double pawn pushes
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if (Type != MV_CAPTURE)
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{
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b1 = pawnPushes & emptySquares;
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b2 = move_pawns<TDELTA_N>(pawnPushes & TRank3BB) & emptySquares;
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if (Type == MV_CHECK)
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{
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// Consider only pawn moves which give direct checks
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b1 &= pos.attacks_from<PAWN>(ksq, Them);
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b2 &= pos.attacks_from<PAWN>(ksq, Them);
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// Add pawn moves which gives discovered check. This is possible only
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// if the pawn is not on the same file as the enemy king, because we
|
|
// don't generate captures.
|
|
if (pawns & target) // For CHECK type target is dc bitboard
|
|
{
|
|
dc1 = move_pawns<TDELTA_N>(pawns & target & ~file_bb(ksq)) & emptySquares;
|
|
dc2 = move_pawns<TDELTA_N>(dc1 & TRank3BB) & emptySquares;
|
|
|
|
b1 |= dc1;
|
|
b2 |= dc2;
|
|
}
|
|
}
|
|
SERIALIZE_MOVES_D(b1, -TDELTA_N);
|
|
SERIALIZE_MOVES_D(b2, -TDELTA_N -TDELTA_N);
|
|
}
|
|
|
|
// En passant captures
|
|
if ((Type == MV_CAPTURE || Type == MV_EVASION) && pos.ep_square() != SQ_NONE)
|
|
{
|
|
assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
|
|
assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
|
|
|
|
// An en passant capture can be an evasion only if the checking piece
|
|
// is the double pushed pawn and so is in the target. Otherwise this
|
|
// is a discovery check and we are forced to do otherwise.
|
|
if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - TDELTA_N))
|
|
return mlist;
|
|
|
|
b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
|
|
|
|
assert(b1 != EmptyBoardBB);
|
|
|
|
while (b1)
|
|
{
|
|
to = pop_1st_bit(&b1);
|
|
(*mlist++).move = make_ep_move(to, pos.ep_square());
|
|
}
|
|
}
|
|
return mlist;
|
|
}
|
|
|
|
template<CastlingSide Side>
|
|
MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, Color us) {
|
|
|
|
Color them = opposite_color(us);
|
|
Square ksq = pos.king_square(us);
|
|
|
|
assert(pos.piece_on(ksq) == make_piece(us, KING));
|
|
|
|
Square rsq = (Side == KING_SIDE ? pos.initial_kr_square(us) : pos.initial_qr_square(us));
|
|
Square s1 = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
|
|
Square s2 = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
|
|
Square s;
|
|
bool illegal = false;
|
|
|
|
assert(pos.piece_on(rsq) == make_piece(us, ROOK));
|
|
|
|
// It is a bit complicated to correctly handle Chess960
|
|
for (s = Min(ksq, s1); s <= Max(ksq, s1); s++)
|
|
if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
|
|
||(pos.attackers_to(s) & pos.pieces_of_color(them)))
|
|
illegal = true;
|
|
|
|
for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)
|
|
if (s != ksq && s != rsq && pos.square_is_occupied(s))
|
|
illegal = true;
|
|
|
|
if ( Side == QUEEN_SIDE
|
|
&& square_file(rsq) == FILE_B
|
|
&& ( pos.piece_on(relative_square(us, SQ_A1)) == make_piece(them, ROOK)
|
|
|| pos.piece_on(relative_square(us, SQ_A1)) == make_piece(them, QUEEN)))
|
|
illegal = true;
|
|
|
|
if (!illegal)
|
|
(*mlist++).move = make_castle_move(ksq, rsq);
|
|
|
|
return mlist;
|
|
}
|
|
|
|
} // namespace
|