/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see .
*/
#include
#include
#include "movegen.h"
#include "position.h"
/// Simple macro to wrap a very common while loop, no facny, no flexibility,
/// hardcoded names 'mlist' and 'from'.
#define SERIALIZE(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
/// Version used for pawns, where the 'from' square is given as a delta from the 'to' square
#define SERIALIZE_PAWNS(b, d) while (b) { Square to = pop_1st_bit(&b); \
(*mlist++).move = make_move(to + (d), to); }
namespace {
enum CastlingSide { KING_SIDE, QUEEN_SIDE };
template
MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, Color us) {
const CastleRight CR[] = { Side ? WHITE_OOO : WHITE_OO,
Side ? BLACK_OOO : BLACK_OO };
if (!pos.can_castle(CR[us]))
return mlist;
// After castling, the rook and king final positions are the same in Chess960
// as they would be in standard chess.
Square kfrom = pos.king_square(us);
Square rfrom = pos.castle_rook_square(CR[us]);
Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
Square rto = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
Bitboard enemies = pos.pieces(flip(us));
assert(!pos.in_check());
assert(pos.piece_on(kfrom) == make_piece(us, KING));
assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
// Unimpeded rule: All the squares between the king's initial and final squares
// (including the final square), and all the squares between the rook's initial
// and final squares (including the final square), must be vacant except for
// the king and castling rook.
for (Square s = std::min(rfrom, rto), e = std::max(rfrom, rto); s <= e; s++)
if (s != kfrom && s != rfrom && !pos.square_is_empty(s))
return mlist;
for (Square s = std::min(kfrom, kto), e = std::max(kfrom, kto); s <= e; s++)
if ( (s != kfrom && s != rfrom && !pos.square_is_empty(s))
||(pos.attackers_to(s) & enemies))
return mlist;
// Because we generate only legal castling moves we need to verify that
// when moving the castling rook we do not discover some hidden checker.
// For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
if (pos.is_chess960())
{
Bitboard occ = pos.occupied_squares();
clear_bit(&occ, rfrom);
if (pos.attackers_to(kto, occ) & enemies)
return mlist;
}
(*mlist++).move = make_castle(kfrom, rfrom);
if (OnlyChecks && !pos.move_gives_check((mlist - 1)->move, CheckInfo(pos)))
mlist--;
return mlist;
}
template
inline Bitboard move_pawns(Bitboard p) {
return Delta == DELTA_N ? p << 8 : Delta == DELTA_S ? p >> 8 :
Delta == DELTA_NE ? p << 9 : Delta == DELTA_SE ? p >> 7 :
Delta == DELTA_NW ? p << 7 : Delta == DELTA_SW ? p >> 9 : p;
}
template
inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard target) {
const Bitboard TFileABB = ( Delta == DELTA_NE
|| Delta == DELTA_SE ? FileABB : FileHBB);
Bitboard b = move_pawns(pawns) & target & ~TFileABB;
SERIALIZE_PAWNS(b, -Delta);
return mlist;
}
template
inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
const Bitboard TFileABB = ( Delta == DELTA_NE
|| Delta == DELTA_SE ? FileABB : FileHBB);
Bitboard b = move_pawns(pawnsOn7) & target;
if (Delta != DELTA_N && Delta != DELTA_S)
b &= ~TFileABB;
while (b)
{
Square to = pop_1st_bit(&b);
if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
(*mlist++).move = make_promotion(to - Delta, to, QUEEN);
if (Type == MV_NON_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
{
(*mlist++).move = make_promotion(to - Delta, to, ROOK);
(*mlist++).move = make_promotion(to - Delta, to, BISHOP);
(*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
}
// Knight-promotion is the only one that can give a check (direct or
// discovered) not already included in the queen-promotion.
if (Type == MV_NON_CAPTURE_CHECK && bit_is_set(StepAttacksBB[W_KNIGHT][to], ksq))
(*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
else
(void)ksq; // Silence a warning under MSVC
}
return mlist;
}
template
MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
// Calculate our parametrized parameters at compile time, named according to
// the point of view of white side.
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
Bitboard b1, b2, dc1, dc2, emptySquares;
Bitboard pawnsOn7 = pos.pieces(PAWN, Us) & TRank7BB;
Bitboard pawnsNotOn7 = pos.pieces(PAWN, Us) & ~TRank7BB;
Bitboard enemies = (Type == MV_EVASION ? pos.pieces(Them) & target:
Type == MV_CAPTURE ? target : pos.pieces(Them));
// Single and double pawn pushes, no promotions
if (Type != MV_CAPTURE)
{
emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
b1 = move_pawns(pawnsNotOn7) & emptySquares;
b2 = move_pawns(b1 & TRank3BB) & emptySquares;
if (Type == MV_EVASION) // Consider only blocking squares
{
b1 &= target;
b2 &= target;
}
if (Type == MV_NON_CAPTURE_CHECK)
{
// Consider only direct checks
b1 &= pos.attacks_from(ksq, Them);
b2 &= pos.attacks_from(ksq, Them);
// 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 discovery check
// promotion has been already generated among captures.
if (pawnsNotOn7 & target) // Target is dc bitboard
{
dc1 = move_pawns(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
dc2 = move_pawns(dc1 & TRank3BB) & emptySquares;
b1 |= dc1;
b2 |= dc2;
}
}
SERIALIZE_PAWNS(b1, -UP);
SERIALIZE_PAWNS(b2, -UP -UP);
}
// Promotions and underpromotions
if (pawnsOn7)
{
if (Type == MV_CAPTURE)
emptySquares = pos.empty_squares();
if (Type == MV_EVASION)
emptySquares &= target;
mlist = generate_promotions(mlist, pawnsOn7, enemies, ksq);
mlist = generate_promotions(mlist, pawnsOn7, enemies, ksq);
mlist = generate_promotions(mlist, pawnsOn7, emptySquares, ksq);
}
// Standard and en-passant captures
if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
{
mlist = generate_pawn_captures(mlist, pawnsNotOn7, enemies);
mlist = generate_pawn_captures(mlist, pawnsNotOn7, enemies);
if (pos.ep_square() != SQ_NONE)
{
assert(rank_of(pos.ep_square()) == (Us == WHITE ? RANK_6 : 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() - UP))
return mlist;
b1 = pawnsNotOn7 & pos.attacks_from(pos.ep_square(), Them);
assert(b1);
while (b1)
(*mlist++).move = make_enpassant(pop_1st_bit(&b1), pos.ep_square());
}
}
return mlist;
}
template
inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
Bitboard dc, Square ksq) {
assert(Pt != KING && Pt != PAWN);
Bitboard checkSqs, b;
Square from;
const Square* pl = pos.piece_list(us, Pt);
if ((from = *pl++) == SQ_NONE)
return mlist;
checkSqs = pos.attacks_from(ksq) & pos.empty_squares();
do
{
if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
|| (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
|| (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
continue;
if (dc && bit_is_set(dc, from))
continue;
b = pos.attacks_from(from) & checkSqs;
SERIALIZE(b);
} while ((from = *pl++) != SQ_NONE);
return mlist;
}
template<>
FORCE_INLINE MoveStack* generate_direct_checks(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
return us == WHITE ? generate_pawn_moves(p, m, dc, ksq)
: generate_pawn_moves(p, m, dc, ksq);
}
template
FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
assert(Pt == PAWN);
return us == WHITE ? generate_pawn_moves(p, m, t, SQ_NONE)
: generate_pawn_moves(p, m, t, SQ_NONE);
}
template
FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
Bitboard b;
Square from;
const Square* pl = pos.piece_list(us, Pt);
if (*pl != SQ_NONE)
{
do {
from = *pl;
b = pos.attacks_from(from) & target;
SERIALIZE(b);
} while (*++pl != SQ_NONE);
}
return mlist;
}
template<>
FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
Square from = pos.king_square(us);
Bitboard b = pos.attacks_from(from) & target;
SERIALIZE(b);
return mlist;
}
} // namespace
/// generate generates all pseudo-legal captures and queen
/// promotions. Returns a pointer to the end of the move list.
///
/// generate generates all pseudo-legal non-captures and
/// underpromotions. Returns a pointer to the end of the move list.
///
/// generate generates all pseudo-legal captures and
/// non-captures. Returns a pointer to the end of the move list.
template
MoveStack* generate(const Position& pos, MoveStack* mlist) {
assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_NON_EVASION);
assert(!pos.in_check());
Color us = pos.side_to_move();
Bitboard target;
if (Type == MV_CAPTURE)
target = pos.pieces(flip(us));
else if (Type == MV_NON_CAPTURE)
target = pos.empty_squares();
else if (Type == MV_NON_EVASION)
target = pos.pieces(flip(us)) | pos.empty_squares();
mlist = generate_piece_moves(pos, mlist, us, target);
mlist = generate_piece_moves(pos, mlist, us, target);
mlist = generate_piece_moves(pos, mlist, us, target);
mlist = generate_piece_moves(pos, mlist, us, target);
mlist = generate_piece_moves(pos, mlist, us, target);
mlist = generate_piece_moves(pos, mlist, us, target);
if (Type != MV_CAPTURE && pos.can_castle(us))
{
mlist = generate_castle_moves(pos, mlist, us);
mlist = generate_castle_moves(pos, mlist, us);
}
return mlist;
}
// Explicit template instantiations
template MoveStack* generate(const Position& pos, MoveStack* mlist);
template MoveStack* generate(const Position& pos, MoveStack* mlist);
template MoveStack* generate(const Position& pos, MoveStack* mlist);
/// generate generates all pseudo-legal non-captures and knight
/// underpromotions that give check. Returns a pointer to the end of the move list.
template<>
MoveStack* generate(const Position& pos, MoveStack* mlist) {
assert(!pos.in_check());
Bitboard b, dc;
Square from;
PieceType pt;
Color us = pos.side_to_move();
Square ksq = pos.king_square(flip(us));
assert(pos.piece_on(ksq) == make_piece(flip(us), KING));
b = dc = pos.discovered_check_candidates();
while (b)
{
from = pop_1st_bit(&b);
pt = type_of(pos.piece_on(from));
if (pt == PAWN)
continue; // Will be generated togheter with direct checks
b = pos.attacks_from(Piece(pt), from) & pos.empty_squares();
if (pt == KING)
b &= ~QueenPseudoAttacks[ksq];
SERIALIZE(b);
}
mlist = generate_direct_checks(pos, mlist, us, dc, ksq);
mlist = generate_direct_checks(pos, mlist, us, dc, ksq);
mlist = generate_direct_checks(pos, mlist, us, dc, ksq);
mlist = generate_direct_checks(pos, mlist, us, dc, ksq);
mlist = generate_direct_checks(pos, mlist, us, dc, ksq);
if (pos.can_castle(us))
{
mlist = generate_castle_moves(pos, mlist, us);
mlist = generate_castle_moves(pos, mlist, us);
}
return mlist;
}
/// generate 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<>
MoveStack* generate(const Position& pos, MoveStack* mlist) {
assert(pos.in_check());
Bitboard b, target;
Square from, checksq;
int checkersCnt = 0;
Color us = pos.side_to_move();
Square ksq = pos.king_square(us);
Bitboard checkers = pos.checkers();
Bitboard sliderAttacks = 0;
assert(pos.piece_on(ksq) == make_piece(us, KING));
assert(checkers);
// Find squares attacked by slider checkers, we will remove them from the king
// evasions set so to skip known illegal moves and avoid to do legality check later.
b = checkers;
do
{
checkersCnt++;
checksq = pop_1st_bit(&b);
assert(color_of(pos.piece_on(checksq)) == flip(us));
switch (type_of(pos.piece_on(checksq)))
{
case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
case QUEEN:
// If queen and king are far we can safely remove all the squares attacked
// in the other direction becuase are not reachable by the king anyway.
if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
sliderAttacks |= QueenPseudoAttacks[checksq];
// Otherwise, if king and queen are adjacent and on a diagonal line, we need to
// use real rook attacks to check if king is safe to move in the other direction.
// For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
else
sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from(checksq);
default:
break;
}
} while (b);
// Generate evasions for king, capture and non capture moves
b = pos.attacks_from(ksq) & ~pos.pieces(us) & ~sliderAttacks;
from = ksq;
SERIALIZE(b);
// Generate evasions for other pieces only if not under a double check
if (checkersCnt > 1)
return mlist;
// Target for blocking evasions or captures of the checking piece
target = squares_between(checksq, ksq) | checkers;
mlist = generate_piece_moves(pos, mlist, us, target);
mlist = generate_piece_moves(pos, mlist, us, target);
mlist = generate_piece_moves(pos, mlist, us, target);
mlist = generate_piece_moves(pos, mlist, us, target);
return generate_piece_moves(pos, mlist, us, target);
}
/// generate generates all the legal moves in the given position
template<>
MoveStack* generate(const Position& pos, MoveStack* mlist) {
MoveStack *last, *cur = mlist;
Bitboard pinned = pos.pinned_pieces();
last = pos.in_check() ? generate(pos, mlist)
: generate(pos, mlist);
while (cur != last)
if (!pos.pl_move_is_legal(cur->move, pinned))
cur->move = (--last)->move;
else
cur++;
return last;
}