277 lines
9.3 KiB
C++
277 lines
9.3 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2021 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 <cassert>
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#include "movegen.h"
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#include "position.h"
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namespace Stockfish {
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namespace {
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template<GenType Type, Direction D>
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ExtMove* make_promotions(ExtMove* moveList, Square to) {
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if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
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*moveList++ = make<PROMOTION>(to - D, to, QUEEN);
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if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
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{
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*moveList++ = make<PROMOTION>(to - D, to, ROOK);
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*moveList++ = make<PROMOTION>(to - D, to, BISHOP);
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*moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
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}
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return moveList;
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}
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template<Color Us, GenType Type>
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ExtMove* generate_pawn_moves(const Position& pos, ExtMove* moveList, Bitboard target) {
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constexpr Color Them = ~Us;
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constexpr Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
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constexpr Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
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constexpr Direction Up = pawn_push(Us);
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constexpr Direction UpRight = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
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constexpr Direction UpLeft = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
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const Bitboard emptySquares = ~pos.pieces();
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const Bitboard enemies = Type == EVASIONS ? pos.checkers()
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: pos.pieces(Them);
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Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
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Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
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// Single and double pawn pushes, no promotions
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if (Type != CAPTURES)
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{
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Bitboard b1 = shift<Up>(pawnsNotOn7) & emptySquares;
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Bitboard b2 = shift<Up>(b1 & TRank3BB) & emptySquares;
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if (Type == EVASIONS) // Consider only blocking squares
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{
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b1 &= target;
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b2 &= target;
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}
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if (Type == QUIET_CHECKS)
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{
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// To make a quiet check, you either make a direct check by pushing a pawn
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// or push a blocker pawn that is not on the same file as the enemy king.
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// Discovered check promotion has been already generated amongst the captures.
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Square ksq = pos.square<KING>(Them);
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Bitboard dcCandidatePawns = pos.blockers_for_king(Them) & ~file_bb(ksq);
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b1 &= pawn_attacks_bb(Them, ksq) | shift< Up>(dcCandidatePawns);
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b2 &= pawn_attacks_bb(Them, ksq) | shift<Up+Up>(dcCandidatePawns);
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}
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while (b1)
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{
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Square to = pop_lsb(b1);
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*moveList++ = make_move(to - Up, to);
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}
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while (b2)
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{
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Square to = pop_lsb(b2);
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*moveList++ = make_move(to - Up - Up, to);
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}
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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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Bitboard b1 = shift<UpRight>(pawnsOn7) & enemies;
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Bitboard b2 = shift<UpLeft >(pawnsOn7) & enemies;
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Bitboard b3 = shift<Up >(pawnsOn7) & emptySquares;
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if (Type == EVASIONS)
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b3 &= target;
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while (b1)
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moveList = make_promotions<Type, UpRight>(moveList, pop_lsb(b1));
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while (b2)
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moveList = make_promotions<Type, UpLeft >(moveList, pop_lsb(b2));
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while (b3)
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moveList = make_promotions<Type, Up >(moveList, pop_lsb(b3));
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}
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// Standard and en passant captures
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if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
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{
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Bitboard b1 = shift<UpRight>(pawnsNotOn7) & enemies;
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Bitboard b2 = shift<UpLeft >(pawnsNotOn7) & enemies;
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while (b1)
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{
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Square to = pop_lsb(b1);
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*moveList++ = make_move(to - UpRight, to);
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}
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while (b2)
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{
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Square to = pop_lsb(b2);
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*moveList++ = make_move(to - UpLeft, to);
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}
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if (pos.ep_square() != SQ_NONE)
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{
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assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
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// An en passant capture cannot resolve a discovered check
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if (Type == EVASIONS && (target & (pos.ep_square() + Up)))
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return moveList;
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b1 = pawnsNotOn7 & pawn_attacks_bb(Them, pos.ep_square());
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assert(b1);
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while (b1)
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*moveList++ = make<EN_PASSANT>(pop_lsb(b1), pos.ep_square());
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}
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}
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return moveList;
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}
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template<Color Us, PieceType Pt, bool Checks>
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ExtMove* generate_moves(const Position& pos, ExtMove* moveList, Bitboard target) {
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static_assert(Pt != KING && Pt != PAWN, "Unsupported piece type in generate_moves()");
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Bitboard bb = pos.pieces(Us, Pt);
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while (bb)
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{
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Square from = pop_lsb(bb);
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Bitboard b = attacks_bb<Pt>(from, pos.pieces()) & target;
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// To check, you either move freely a blocker or make a direct check.
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if (Checks && (Pt == QUEEN || !(pos.blockers_for_king(~Us) & from)))
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b &= pos.check_squares(Pt);
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while (b)
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*moveList++ = make_move(from, pop_lsb(b));
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}
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return moveList;
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}
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template<Color Us, GenType Type>
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ExtMove* generate_all(const Position& pos, ExtMove* moveList) {
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static_assert(Type != LEGAL, "Unsupported type in generate_all()");
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constexpr bool Checks = Type == QUIET_CHECKS; // Reduce template instantiations
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const Square ksq = pos.square<KING>(Us);
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Bitboard target;
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// Skip generating non-king moves when in double check
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if (Type != EVASIONS || !more_than_one(pos.checkers()))
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{
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target = Type == EVASIONS ? between_bb(ksq, lsb(pos.checkers()))
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: Type == NON_EVASIONS ? ~pos.pieces( Us)
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: Type == CAPTURES ? pos.pieces(~Us)
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: ~pos.pieces( ); // QUIETS || QUIET_CHECKS
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moveList = generate_pawn_moves<Us, Type>(pos, moveList, target);
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moveList = generate_moves<Us, KNIGHT, Checks>(pos, moveList, target);
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moveList = generate_moves<Us, BISHOP, Checks>(pos, moveList, target);
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moveList = generate_moves<Us, ROOK, Checks>(pos, moveList, target);
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moveList = generate_moves<Us, QUEEN, Checks>(pos, moveList, target);
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}
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if (!Checks || pos.blockers_for_king(~Us) & ksq)
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{
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Bitboard b = attacks_bb<KING>(ksq) & (Type == EVASIONS ? ~pos.pieces(Us) : target);
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if (Checks)
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b &= ~attacks_bb<QUEEN>(pos.square<KING>(~Us));
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while (b)
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*moveList++ = make_move(ksq, pop_lsb(b));
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if ((Type == QUIETS || Type == NON_EVASIONS) && pos.can_castle(Us & ANY_CASTLING))
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for (CastlingRights cr : { Us & KING_SIDE, Us & QUEEN_SIDE } )
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if (!pos.castling_impeded(cr) && pos.can_castle(cr))
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*moveList++ = make<CASTLING>(ksq, pos.castling_rook_square(cr));
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}
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return moveList;
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}
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} // namespace
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/// <CAPTURES> Generates all pseudo-legal captures plus queen promotions
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/// <QUIETS> Generates all pseudo-legal non-captures and underpromotions
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/// <EVASIONS> Generates all pseudo-legal check evasions when the side to move is in check
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/// <QUIET_CHECKS> Generates all pseudo-legal non-captures giving check, except castling and promotions
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/// <NON_EVASIONS> Generates all pseudo-legal captures and non-captures
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///
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/// Returns a pointer to the end of the move list.
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template<GenType Type>
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ExtMove* generate(const Position& pos, ExtMove* moveList) {
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static_assert(Type != LEGAL, "Unsupported type in generate()");
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assert((Type == EVASIONS) == (bool)pos.checkers());
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Color us = pos.side_to_move();
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return us == WHITE ? generate_all<WHITE, Type>(pos, moveList)
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: generate_all<BLACK, Type>(pos, moveList);
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}
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// Explicit template instantiations
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template ExtMove* generate<CAPTURES>(const Position&, ExtMove*);
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template ExtMove* generate<QUIETS>(const Position&, ExtMove*);
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template ExtMove* generate<EVASIONS>(const Position&, ExtMove*);
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template ExtMove* generate<QUIET_CHECKS>(const Position&, ExtMove*);
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template ExtMove* generate<NON_EVASIONS>(const Position&, ExtMove*);
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/// generate<LEGAL> generates all the legal moves in the given position
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template<>
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ExtMove* generate<LEGAL>(const Position& pos, ExtMove* moveList) {
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Color us = pos.side_to_move();
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Bitboard pinned = pos.blockers_for_king(us) & pos.pieces(us);
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Square ksq = pos.square<KING>(us);
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ExtMove* cur = moveList;
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moveList = pos.checkers() ? generate<EVASIONS >(pos, moveList)
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: generate<NON_EVASIONS>(pos, moveList);
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while (cur != moveList)
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if ( ((pinned && pinned & from_sq(*cur)) || from_sq(*cur) == ksq || type_of(*cur) == EN_PASSANT)
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&& !pos.legal(*cur))
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*cur = (--moveList)->move;
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else
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++cur;
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return moveList;
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}
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} // namespace Stockfish
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