/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
+ Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include "movegen.h"
+
#include <cassert>
+#include <initializer_list>
-#include "movegen.h"
+#include "bitboard.h"
#include "position.h"
+namespace Stockfish {
+
namespace {
- template<GenType Type, Direction D>
- ExtMove* make_promotions(ExtMove* moveList, Square to, Square ksq) {
+template<GenType Type, Direction D, bool Enemy>
+ExtMove* make_promotions(ExtMove* moveList, [[maybe_unused]] Square to) {
- if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
- {
+ constexpr bool all = Type == EVASIONS || Type == NON_EVASIONS;
+
+ if constexpr (Type == CAPTURES || all)
*moveList++ = make<PROMOTION>(to - D, to, QUEEN);
- if (attacks_bb<KNIGHT>(to) & ksq)
- *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
- }
- if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
+ if constexpr ((Type == CAPTURES && Enemy) || (Type == QUIETS && !Enemy) || all)
{
*moveList++ = make<PROMOTION>(to - D, to, ROOK);
*moveList++ = make<PROMOTION>(to - D, to, BISHOP);
- if (!(attacks_bb<KNIGHT>(to) & ksq))
- *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
+ *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
}
return moveList;
- }
+}
- template<Color Us, GenType Type>
- ExtMove* generate_pawn_moves(const Position& pos, ExtMove* moveList, Bitboard target) {
+template<Color Us, GenType Type>
+ExtMove* generate_pawn_moves(const Position& pos, ExtMove* moveList, Bitboard target) {
constexpr Color Them = ~Us;
- constexpr Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
- constexpr Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
+ constexpr Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
+ constexpr Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
constexpr Direction Up = pawn_push(Us);
constexpr Direction UpRight = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
constexpr Direction UpLeft = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
- const Square ksq = pos.square<KING>(Them);
- Bitboard emptySquares;
+ const Bitboard emptySquares = ~pos.pieces();
+ const Bitboard enemies = Type == EVASIONS ? pos.checkers() : pos.pieces(Them);
- Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
+ Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
- Bitboard enemies = (Type == EVASIONS ? pos.pieces(Them) & target:
- Type == CAPTURES ? target : pos.pieces(Them));
-
// Single and double pawn pushes, no promotions
- if (Type != CAPTURES)
+ if constexpr (Type != CAPTURES)
{
- emptySquares = (Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces());
-
- Bitboard b1 = shift<Up>(pawnsNotOn7) & emptySquares;
+ Bitboard b1 = shift<Up>(pawnsNotOn7) & emptySquares;
Bitboard b2 = shift<Up>(b1 & TRank3BB) & emptySquares;
- if (Type == EVASIONS) // Consider only blocking squares
+ if constexpr (Type == EVASIONS) // Consider only blocking squares
{
b1 &= target;
b2 &= target;
}
- if (Type == QUIET_CHECKS)
+ if constexpr (Type == QUIET_CHECKS)
{
- b1 &= pawn_attacks_bb(Them, ksq);
- b2 &= pawn_attacks_bb(Them, ksq);
-
- // Add pawn pushes which give discovered check. This is possible only
- // if the pawn is not on the same file as the enemy king, because we
- // don't generate captures. Note that a possible discovered check
- // promotion has been already generated amongst the captures.
- Bitboard dcCandidateQuiets = pos.blockers_for_king(Them) & pawnsNotOn7;
- if (dcCandidateQuiets)
- {
- Bitboard dc1 = shift<Up>(dcCandidateQuiets) & emptySquares & ~file_bb(ksq);
- Bitboard dc2 = shift<Up>(dc1 & TRank3BB) & emptySquares;
-
- b1 |= dc1;
- b2 |= dc2;
- }
+ // To make a quiet check, you either make a direct check by pushing a pawn
+ // or push a blocker pawn that is not on the same file as the enemy king.
+ // Discovered check promotion has been already generated amongst the captures.
+ Square ksq = pos.square<KING>(Them);
+ Bitboard dcCandidatePawns = pos.blockers_for_king(Them) & ~file_bb(ksq);
+ b1 &= pawn_attacks_bb(Them, ksq) | shift<Up>(dcCandidatePawns);
+ b2 &= pawn_attacks_bb(Them, ksq) | shift<Up + Up>(dcCandidatePawns);
}
while (b1)
{
- Square to = pop_lsb(&b1);
+ Square to = pop_lsb(b1);
*moveList++ = make_move(to - Up, to);
}
while (b2)
{
- Square to = pop_lsb(&b2);
+ Square to = pop_lsb(b2);
*moveList++ = make_move(to - Up - Up, to);
}
}
// Promotions and underpromotions
if (pawnsOn7)
{
- if (Type == CAPTURES)
- emptySquares = ~pos.pieces();
-
- if (Type == EVASIONS)
- emptySquares &= target;
-
Bitboard b1 = shift<UpRight>(pawnsOn7) & enemies;
- Bitboard b2 = shift<UpLeft >(pawnsOn7) & enemies;
- Bitboard b3 = shift<Up >(pawnsOn7) & emptySquares;
+ Bitboard b2 = shift<UpLeft>(pawnsOn7) & enemies;
+ Bitboard b3 = shift<Up>(pawnsOn7) & emptySquares;
+
+ if constexpr (Type == EVASIONS)
+ b3 &= target;
while (b1)
- moveList = make_promotions<Type, UpRight>(moveList, pop_lsb(&b1), ksq);
+ moveList = make_promotions<Type, UpRight, true>(moveList, pop_lsb(b1));
while (b2)
- moveList = make_promotions<Type, UpLeft >(moveList, pop_lsb(&b2), ksq);
+ moveList = make_promotions<Type, UpLeft, true>(moveList, pop_lsb(b2));
while (b3)
- moveList = make_promotions<Type, Up >(moveList, pop_lsb(&b3), ksq);
+ moveList = make_promotions<Type, Up, false>(moveList, pop_lsb(b3));
}
// Standard and en passant captures
- if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
+ if constexpr (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
{
Bitboard b1 = shift<UpRight>(pawnsNotOn7) & enemies;
- Bitboard b2 = shift<UpLeft >(pawnsNotOn7) & enemies;
+ Bitboard b2 = shift<UpLeft>(pawnsNotOn7) & enemies;
while (b1)
{
- Square to = pop_lsb(&b1);
+ Square to = pop_lsb(b1);
*moveList++ = make_move(to - UpRight, to);
}
while (b2)
{
- Square to = pop_lsb(&b2);
+ Square to = pop_lsb(b2);
*moveList++ = make_move(to - UpLeft, to);
}
{
assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
- // 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 == EVASIONS && !(target & (pos.ep_square() - Up)))
+ // An en passant capture cannot resolve a discovered check
+ if (Type == EVASIONS && (target & (pos.ep_square() + Up)))
return moveList;
b1 = pawnsNotOn7 & pawn_attacks_bb(Them, pos.ep_square());
assert(b1);
while (b1)
- *moveList++ = make<EN_PASSANT>(pop_lsb(&b1), pos.ep_square());
+ *moveList++ = make<EN_PASSANT>(pop_lsb(b1), pos.ep_square());
}
}
return moveList;
- }
+}
- template<PieceType Pt, bool Checks>
- ExtMove* generate_moves(const Position& pos, ExtMove* moveList, Bitboard piecesToMove, Bitboard target) {
+template<Color Us, PieceType Pt, bool Checks>
+ExtMove* generate_moves(const Position& pos, ExtMove* moveList, Bitboard target) {
static_assert(Pt != KING && Pt != PAWN, "Unsupported piece type in generate_moves()");
- Bitboard bb = piecesToMove & pos.pieces(Pt);
-
- while (bb) {
- Square from = pop_lsb(&bb);
+ Bitboard bb = pos.pieces(Us, Pt);
- if (Checks && (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
- && !(attacks_bb<Pt>(from) & target & pos.check_squares(Pt)))
- continue;
-
- Bitboard b = attacks_bb<Pt>(from, pos.pieces()) & target;
+ while (bb)
+ {
+ Square from = pop_lsb(bb);
+ Bitboard b = attacks_bb<Pt>(from, pos.pieces()) & target;
- if (Checks)
+ // To check, you either move freely a blocker or make a direct check.
+ if (Checks && (Pt == QUEEN || !(pos.blockers_for_king(~Us) & from)))
b &= pos.check_squares(Pt);
while (b)
- *moveList++ = make_move(from, pop_lsb(&b));
+ *moveList++ = make_move(from, pop_lsb(b));
}
return moveList;
- }
+}
- template<Color Us, GenType Type>
- ExtMove* generate_all(const Position& pos, ExtMove* moveList) {
+template<Color Us, GenType Type>
+ExtMove* generate_all(const Position& pos, ExtMove* moveList) {
static_assert(Type != LEGAL, "Unsupported type in generate_all()");
- constexpr bool Checks = Type == QUIET_CHECKS; // Reduce template instantations
- Bitboard target, piecesToMove = pos.pieces(Us);
-
- if(Type == QUIET_CHECKS)
- piecesToMove &= ~pos.blockers_for_king(~Us);
+ constexpr bool Checks = Type == QUIET_CHECKS; // Reduce template instantiations
+ const Square ksq = pos.square<KING>(Us);
+ Bitboard target;
- switch (Type)
+ // Skip generating non-king moves when in double check
+ if (Type != EVASIONS || !more_than_one(pos.checkers()))
{
- case CAPTURES:
- target = pos.pieces(~Us);
- break;
- case QUIETS:
- case QUIET_CHECKS:
- target = ~pos.pieces();
- break;
- case EVASIONS:
- {
- Square checksq = lsb(pos.checkers());
- target = between_bb(pos.square<KING>(Us), checksq) | checksq;
- break;
- }
- case NON_EVASIONS:
- target = ~pos.pieces(Us);
- break;
+ target = Type == EVASIONS ? between_bb(ksq, lsb(pos.checkers()))
+ : Type == NON_EVASIONS ? ~pos.pieces(Us)
+ : Type == CAPTURES ? pos.pieces(~Us)
+ : ~pos.pieces(); // QUIETS || QUIET_CHECKS
+
+ moveList = generate_pawn_moves<Us, Type>(pos, moveList, target);
+ moveList = generate_moves<Us, KNIGHT, Checks>(pos, moveList, target);
+ moveList = generate_moves<Us, BISHOP, Checks>(pos, moveList, target);
+ moveList = generate_moves<Us, ROOK, Checks>(pos, moveList, target);
+ moveList = generate_moves<Us, QUEEN, Checks>(pos, moveList, target);
}
- moveList = generate_pawn_moves<Us, Type>(pos, moveList, target);
- moveList = generate_moves<KNIGHT, Checks>(pos, moveList, piecesToMove, target);
- moveList = generate_moves<BISHOP, Checks>(pos, moveList, piecesToMove, target);
- moveList = generate_moves< ROOK, Checks>(pos, moveList, piecesToMove, target);
- moveList = generate_moves< QUEEN, Checks>(pos, moveList, piecesToMove, target);
-
- if (Type != QUIET_CHECKS && Type != EVASIONS)
+ if (!Checks || pos.blockers_for_king(~Us) & ksq)
{
- Square ksq = pos.square<KING>(Us);
- Bitboard b = attacks_bb<KING>(ksq) & target;
+ Bitboard b = attacks_bb<KING>(ksq) & (Type == EVASIONS ? ~pos.pieces(Us) : target);
+ if (Checks)
+ b &= ~attacks_bb<QUEEN>(pos.square<KING>(~Us));
+
while (b)
- *moveList++ = make_move(ksq, pop_lsb(&b));
+ *moveList++ = make_move(ksq, pop_lsb(b));
- if ((Type != CAPTURES) && pos.can_castle(Us & ANY_CASTLING))
- for (CastlingRights cr : { Us & KING_SIDE, Us & QUEEN_SIDE } )
+ if ((Type == QUIETS || Type == NON_EVASIONS) && pos.can_castle(Us & ANY_CASTLING))
+ for (CastlingRights cr : {Us & KING_SIDE, Us & QUEEN_SIDE})
if (!pos.castling_impeded(cr) && pos.can_castle(cr))
*moveList++ = make<CASTLING>(ksq, pos.castling_rook_square(cr));
}
return moveList;
- }
-
-} // namespace
+}
+} // namespace
-/// <CAPTURES> Generates all pseudo-legal captures plus queen and checking knight promotions
-/// <QUIETS> Generates all pseudo-legal non-captures and underpromotions(except checking knight)
-/// <NON_EVASIONS> Generates all pseudo-legal captures and non-captures
-///
-/// Returns a pointer to the end of the move list.
+// <CAPTURES> Generates all pseudo-legal captures plus queen promotions
+// <QUIETS> Generates all pseudo-legal non-captures and underpromotions
+// <EVASIONS> Generates all pseudo-legal check evasions
+// <NON_EVASIONS> Generates all pseudo-legal captures and non-captures
+// <QUIET_CHECKS> Generates all pseudo-legal non-captures giving check,
+// except castling and promotions
+//
+// Returns a pointer to the end of the move list.
template<GenType Type>
ExtMove* generate(const Position& pos, ExtMove* moveList) {
- static_assert(Type == CAPTURES || Type == QUIETS || Type == NON_EVASIONS, "Unsupported type in generate()");
- assert(!pos.checkers());
+ static_assert(Type != LEGAL, "Unsupported type in generate()");
+ assert((Type == EVASIONS) == bool(pos.checkers()));
- Color us = pos.side_to_move();
+ Color us = pos.side_to_move();
- return us == WHITE ? generate_all<WHITE, Type>(pos, moveList)
- : generate_all<BLACK, Type>(pos, moveList);
+ return us == WHITE ? generate_all<WHITE, Type>(pos, moveList)
+ : generate_all<BLACK, Type>(pos, moveList);
}
// Explicit template instantiations
template ExtMove* generate<CAPTURES>(const Position&, ExtMove*);
template ExtMove* generate<QUIETS>(const Position&, ExtMove*);
+template ExtMove* generate<EVASIONS>(const Position&, ExtMove*);
+template ExtMove* generate<QUIET_CHECKS>(const Position&, ExtMove*);
template ExtMove* generate<NON_EVASIONS>(const Position&, ExtMove*);
-/// generate<QUIET_CHECKS> generates all pseudo-legal non-captures.
-/// Returns a pointer to the end of the move list.
-template<>
-ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
-
- assert(!pos.checkers());
-
- Color us = pos.side_to_move();
- Bitboard dc = pos.blockers_for_king(~us) & pos.pieces(us) & ~pos.pieces(PAWN);
-
- while (dc)
- {
- Square from = pop_lsb(&dc);
- PieceType pt = type_of(pos.piece_on(from));
-
- Bitboard b = attacks_bb(pt, from, pos.pieces()) & ~pos.pieces();
-
- if (pt == KING)
- b &= ~attacks_bb<QUEEN>(pos.square<KING>(~us));
-
- while (b)
- *moveList++ = make_move(from, pop_lsb(&b));
- }
-
- return us == WHITE ? generate_all<WHITE, QUIET_CHECKS>(pos, moveList)
- : generate_all<BLACK, QUIET_CHECKS>(pos, moveList);
-}
-
+// generate<LEGAL> generates all the legal moves in the given position
-/// generate<EVASIONS> generates all pseudo-legal check evasions when the side
-/// to move is in check. Returns a pointer to the end of the move list.
template<>
-ExtMove* generate<EVASIONS>(const Position& pos, ExtMove* moveList) {
-
- assert(pos.checkers());
-
- Color us = pos.side_to_move();
- Square ksq = pos.square<KING>(us);
- Bitboard sliderAttacks = 0;
- Bitboard sliders = pos.checkers() & ~pos.pieces(KNIGHT, PAWN);
-
- // Find all the squares attacked by slider checkers. We will remove them from
- // the king evasions in order to skip known illegal moves, which avoids any
- // useless legality checks later on.
- while (sliders)
- sliderAttacks |= line_bb(ksq, pop_lsb(&sliders)) & ~pos.checkers();
+ExtMove* generate<LEGAL>(const Position& pos, ExtMove* moveList) {
- // Generate evasions for king, capture and non capture moves
- Bitboard b = attacks_bb<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
- while (b)
- *moveList++ = make_move(ksq, pop_lsb(&b));
+ Color us = pos.side_to_move();
+ Bitboard pinned = pos.blockers_for_king(us) & pos.pieces(us);
+ Square ksq = pos.square<KING>(us);
+ ExtMove* cur = moveList;
- if (more_than_one(pos.checkers()))
- return moveList; // Double check, only a king move can save the day
+ moveList =
+ pos.checkers() ? generate<EVASIONS>(pos, moveList) : generate<NON_EVASIONS>(pos, moveList);
+ while (cur != moveList)
+ if (((pinned & from_sq(*cur)) || from_sq(*cur) == ksq || type_of(*cur) == EN_PASSANT)
+ && !pos.legal(*cur))
+ *cur = (--moveList)->move;
+ else
+ ++cur;
- // Generate blocking evasions or captures of the checking piece
- return us == WHITE ? generate_all<WHITE, EVASIONS>(pos, moveList)
- : generate_all<BLACK, EVASIONS>(pos, moveList);
+ return moveList;
}
-
-/// generate<LEGAL> generates all the legal moves in the given position
-
-template<>
-ExtMove* generate<LEGAL>(const Position& pos, ExtMove* moveList) {
-
- Color us = pos.side_to_move();
- Bitboard pinned = pos.blockers_for_king(us) & pos.pieces(us);
- Square ksq = pos.square<KING>(us);
- ExtMove* cur = moveList;
-
- moveList = pos.checkers() ? generate<EVASIONS >(pos, moveList)
- : generate<NON_EVASIONS>(pos, moveList);
- while (cur != moveList)
- if ( (pinned || from_sq(*cur) == ksq || type_of(*cur) == EN_PASSANT)
- && !pos.legal(*cur))
- *cur = (--moveList)->move;
- else
- ++cur;
-
- return moveList;
-}
+} // namespace Stockfish
projects / stockfish / blobdiff