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421 lines
14 KiB
C++
421 lines
14 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) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, 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 "movegen.h"
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#include "position.h"
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namespace {
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template<CastlingRight Cr, bool Checks, bool Chess960>
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ExtMove* generate_castling(const Position& pos, ExtMove* moveList, Color us) {
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static const bool KingSide = (Cr == WHITE_OO || Cr == BLACK_OO);
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if (pos.castling_impeded(Cr) || !pos.can_castle(Cr))
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return moveList;
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// After castling, the rook and king final positions are the same in Chess960
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// as they would be in standard chess.
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Square kfrom = pos.square<KING>(us);
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Square rfrom = pos.castling_rook_square(Cr);
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Square kto = relative_square(us, KingSide ? SQ_G1 : SQ_C1);
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Bitboard enemies = pos.pieces(~us);
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assert(!pos.checkers());
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const Direction K = Chess960 ? kto > kfrom ? WEST : EAST
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: KingSide ? WEST : EAST;
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for (Square s = kto; s != kfrom; s += K)
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if (pos.attackers_to(s) & enemies)
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return moveList;
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// Because we generate only legal castling moves we need to verify that
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// when moving the castling rook we do not discover some hidden checker.
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// For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
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if (Chess960 && (attacks_bb<ROOK>(kto, pos.pieces() ^ rfrom) & pos.pieces(~us, ROOK, QUEEN)))
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return moveList;
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Move m = make<CASTLING>(kfrom, rfrom);
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if (Checks && !pos.gives_check(m))
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return moveList;
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*moveList++ = m;
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return moveList;
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}
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template<GenType Type, Direction D>
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ExtMove* make_promotions(ExtMove* moveList, Square to, Square ksq) {
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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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// Knight promotion is the only promotion that can give a direct check
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// that's not already included in the queen promotion.
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if (Type == QUIET_CHECKS && (PseudoAttacks[KNIGHT][to] & ksq))
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*moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
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else
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(void)ksq; // Silence a warning under MSVC
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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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// Compute our parametrized parameters at compile time, named according to
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// the point of view of white side.
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
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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 Direction Up = (Us == WHITE ? NORTH : SOUTH);
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const Direction Right = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
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const Direction Left = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
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Bitboard emptySquares;
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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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Bitboard enemies = (Type == EVASIONS ? pos.pieces(Them) & target:
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Type == CAPTURES ? target : pos.pieces(Them));
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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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emptySquares = (Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces());
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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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Square ksq = pos.square<KING>(Them);
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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 pushes which give 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
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// don't generate captures. Note that a possible discovery check
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// promotion has been already generated amongst the captures.
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Bitboard dcCandidates = pos.discovered_check_candidates();
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if (pawnsNotOn7 & dcCandidates)
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{
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Bitboard dc1 = shift<Up>(pawnsNotOn7 & dcCandidates) & emptySquares & ~file_bb(ksq);
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Bitboard dc2 = shift<Up>(dc1 & TRank3BB) & emptySquares;
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b1 |= dc1;
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b2 |= dc2;
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}
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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 && (Type != EVASIONS || (target & TRank8BB)))
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{
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if (Type == CAPTURES)
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emptySquares = ~pos.pieces();
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if (Type == EVASIONS)
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emptySquares &= target;
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Bitboard b1 = shift<Right>(pawnsOn7) & enemies;
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Bitboard b2 = shift<Left >(pawnsOn7) & enemies;
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Bitboard b3 = shift<Up >(pawnsOn7) & emptySquares;
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Square ksq = pos.square<KING>(Them);
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while (b1)
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moveList = make_promotions<Type, Right>(moveList, pop_lsb(&b1), ksq);
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while (b2)
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moveList = make_promotions<Type, Left >(moveList, pop_lsb(&b2), ksq);
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while (b3)
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moveList = make_promotions<Type, Up >(moveList, pop_lsb(&b3), ksq);
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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<Right>(pawnsNotOn7) & enemies;
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Bitboard b2 = shift<Left >(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 - Right, 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 - Left, 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 can be an evasion only if the checking piece
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// is the double pushed pawn and so is in the target. Otherwise this
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// is a discovery check and we are forced to do otherwise.
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if (Type == EVASIONS && !(target & (pos.ep_square() - Up)))
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return moveList;
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b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
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assert(b1);
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while (b1)
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*moveList++ = make<ENPASSANT>(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<PieceType Pt, bool Checks>
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ExtMove* generate_moves(const Position& pos, ExtMove* moveList, Color us,
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Bitboard target) {
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assert(Pt != KING && Pt != PAWN);
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const Square* pl = pos.squares<Pt>(us);
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for (Square from = *pl; from != SQ_NONE; from = *++pl)
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{
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if (Checks)
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{
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if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
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&& !(PseudoAttacks[Pt][from] & target & pos.check_squares(Pt)))
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continue;
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if (pos.discovered_check_candidates() & from)
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continue;
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}
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Bitboard b = pos.attacks_from<Pt>(from) & target;
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if (Checks)
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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, Bitboard target) {
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const bool Checks = Type == QUIET_CHECKS;
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moveList = generate_pawn_moves<Us, Type>(pos, moveList, target);
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moveList = generate_moves<KNIGHT, Checks>(pos, moveList, Us, target);
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moveList = generate_moves<BISHOP, Checks>(pos, moveList, Us, target);
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moveList = generate_moves< ROOK, Checks>(pos, moveList, Us, target);
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moveList = generate_moves< QUEEN, Checks>(pos, moveList, Us, target);
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if (Type != QUIET_CHECKS && Type != EVASIONS)
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{
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Square ksq = pos.square<KING>(Us);
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Bitboard b = pos.attacks_from<KING>(ksq) & target;
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while (b)
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*moveList++ = make_move(ksq, pop_lsb(&b));
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}
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if (Type != CAPTURES && Type != EVASIONS && pos.can_castle(Us))
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{
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if (pos.is_chess960())
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{
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moveList = generate_castling<MakeCastling<Us, KING_SIDE>::right, Checks, true>(pos, moveList, Us);
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moveList = generate_castling<MakeCastling<Us, QUEEN_SIDE>::right, Checks, true>(pos, moveList, Us);
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}
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else
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{
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moveList = generate_castling<MakeCastling<Us, KING_SIDE>::right, Checks, false>(pos, moveList, Us);
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moveList = generate_castling<MakeCastling<Us, QUEEN_SIDE>::right, Checks, false>(pos, moveList, Us);
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}
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}
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return moveList;
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}
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} // namespace
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/// generate<CAPTURES> 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<QUIETS> 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<NON_EVASIONS> 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<GenType Type>
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ExtMove* generate(const Position& pos, ExtMove* moveList) {
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assert(Type == CAPTURES || Type == QUIETS || Type == NON_EVASIONS);
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assert(!pos.checkers());
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Color us = pos.side_to_move();
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Bitboard target = Type == CAPTURES ? pos.pieces(~us)
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: Type == QUIETS ? ~pos.pieces()
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: Type == NON_EVASIONS ? ~pos.pieces(us) : 0;
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return us == WHITE ? generate_all<WHITE, Type>(pos, moveList, target)
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: generate_all<BLACK, Type>(pos, moveList, target);
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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<NON_EVASIONS>(const Position&, ExtMove*);
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/// generate<QUIET_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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ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
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assert(!pos.checkers());
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Color us = pos.side_to_move();
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Bitboard dc = pos.discovered_check_candidates();
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while (dc)
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{
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Square from = pop_lsb(&dc);
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PieceType pt = type_of(pos.piece_on(from));
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if (pt == PAWN)
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continue; // Will be generated together with direct checks
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Bitboard b = pos.attacks_from(pt, from) & ~pos.pieces();
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if (pt == KING)
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b &= ~PseudoAttacks[QUEEN][pos.square<KING>(~us)];
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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 us == WHITE ? generate_all<WHITE, QUIET_CHECKS>(pos, moveList, ~pos.pieces())
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: generate_all<BLACK, QUIET_CHECKS>(pos, moveList, ~pos.pieces());
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}
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/// generate<EVASIONS> generates all pseudo-legal check evasions when the side
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/// to move is in check. Returns a pointer to the end of the move list.
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template<>
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ExtMove* generate<EVASIONS>(const Position& pos, ExtMove* moveList) {
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assert(pos.checkers());
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Color us = pos.side_to_move();
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Square ksq = pos.square<KING>(us);
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Bitboard sliderAttacks = 0;
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Bitboard sliders = pos.checkers() & ~pos.pieces(KNIGHT, PAWN);
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// Find all the squares attacked by slider checkers. We will remove them from
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// the king evasions in order to skip known illegal moves, which avoids any
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// useless legality checks later on.
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while (sliders)
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{
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Square checksq = pop_lsb(&sliders);
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sliderAttacks |= LineBB[checksq][ksq] ^ checksq;
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}
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// Generate evasions for king, capture and non capture moves
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Bitboard b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
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while (b)
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*moveList++ = make_move(ksq, pop_lsb(&b));
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if (more_than_one(pos.checkers()))
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return moveList; // Double check, only a king move can save the day
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// Generate blocking evasions or captures of the checking piece
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Square checksq = lsb(pos.checkers());
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Bitboard target = between_bb(checksq, ksq) | checksq;
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return us == WHITE ? generate_all<WHITE, EVASIONS>(pos, moveList, target)
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: generate_all<BLACK, EVASIONS>(pos, moveList, target);
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}
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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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Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
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Square ksq = pos.square<KING>(pos.side_to_move());
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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 || from_sq(*cur) == ksq || type_of(*cur) == ENPASSANT)
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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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