/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ 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 "position.h"
+
#include <algorithm>
+#include <atomic>
#include <cassert>
-#include <cstring> // For std::memset, std::memcmp
+#include <cctype>
+#include <cstddef>
+#include <cstring>
+#include <initializer_list>
#include <iomanip>
+#include <iostream>
#include <sstream>
+#include <string_view>
+#include <utility>
#include "bitboard.h"
#include "misc.h"
#include "movegen.h"
-#include "position.h"
+#include "nnue/nnue_common.h"
+#include "syzygy/tbprobe.h"
#include "thread.h"
#include "tt.h"
#include "uci.h"
using std::string;
+namespace Stockfish {
+
namespace Zobrist {
- Key psq[PIECE_NB][SQUARE_NB];
- Key enpassant[FILE_NB];
- Key castling[CASTLING_RIGHT_NB];
- Key side;
+Key psq[PIECE_NB][SQUARE_NB];
+Key enpassant[FILE_NB];
+Key castling[CASTLING_RIGHT_NB];
+Key side, noPawns;
}
namespace {
-const string PieceToChar(" PNBRQK pnbrqk");
-
-// min_attacker() is a helper function used by see() to locate the least
-// valuable attacker for the side to move, remove the attacker we just found
-// from the bitboards and scan for new X-ray attacks behind it.
-
-template<int Pt>
-PieceType min_attacker(const Bitboard* bb, Square to, Bitboard stmAttackers,
- Bitboard& occupied, Bitboard& attackers) {
-
- Bitboard b = stmAttackers & bb[Pt];
- if (!b)
- return min_attacker<Pt+1>(bb, to, stmAttackers, occupied, attackers);
-
- occupied ^= b & ~(b - 1);
-
- if (Pt == PAWN || Pt == BISHOP || Pt == QUEEN)
- attackers |= attacks_bb<BISHOP>(to, occupied) & (bb[BISHOP] | bb[QUEEN]);
+constexpr std::string_view PieceToChar(" PNBRQK pnbrqk");
- if (Pt == ROOK || Pt == QUEEN)
- attackers |= attacks_bb<ROOK>(to, occupied) & (bb[ROOK] | bb[QUEEN]);
+constexpr Piece Pieces[] = {W_PAWN, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING,
+ B_PAWN, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING};
+} // namespace
- attackers &= occupied; // After X-ray that may add already processed pieces
- return (PieceType)Pt;
-}
-
-template<>
-PieceType min_attacker<KING>(const Bitboard*, Square, Bitboard, Bitboard&, Bitboard&) {
- return KING; // No need to update bitboards: it is the last cycle
-}
-} // namespace
+// Returns an ASCII representation of the position
+std::ostream& operator<<(std::ostream& os, const Position& pos) {
+ os << "\n +---+---+---+---+---+---+---+---+\n";
-/// operator<<(Position) returns an ASCII representation of the position
+ for (Rank r = RANK_8; r >= RANK_1; --r)
+ {
+ for (File f = FILE_A; f <= FILE_H; ++f)
+ os << " | " << PieceToChar[pos.piece_on(make_square(f, r))];
-std::ostream& operator<<(std::ostream& os, const Position& pos) {
+ os << " | " << (1 + r) << "\n +---+---+---+---+---+---+---+---+\n";
+ }
- os << "\n +---+---+---+---+---+---+---+---+\n";
+ os << " a b c d e f g h\n"
+ << "\nFen: " << pos.fen() << "\nKey: " << std::hex << std::uppercase << std::setfill('0')
+ << std::setw(16) << pos.key() << std::setfill(' ') << std::dec << "\nCheckers: ";
- for (Rank r = RANK_8; r >= RANK_1; --r)
- {
- for (File f = FILE_A; f <= FILE_H; ++f)
- os << " | " << PieceToChar[pos.piece_on(make_square(f, r))];
+ for (Bitboard b = pos.checkers(); b;)
+ os << UCI::square(pop_lsb(b)) << " ";
- os << " |\n +---+---+---+---+---+---+---+---+\n";
- }
+ if (int(Tablebases::MaxCardinality) >= popcount(pos.pieces()) && !pos.can_castle(ANY_CASTLING))
+ {
+ StateInfo st;
+ ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
- os << "\nFen: " << pos.fen() << "\nKey: " << std::hex << std::uppercase
- << std::setfill('0') << std::setw(16) << pos.key() << std::dec << "\nCheckers: ";
+ Position p;
+ p.set(pos.fen(), pos.is_chess960(), &st, pos.this_thread());
+ Tablebases::ProbeState s1, s2;
+ Tablebases::WDLScore wdl = Tablebases::probe_wdl(p, &s1);
+ int dtz = Tablebases::probe_dtz(p, &s2);
+ os << "\nTablebases WDL: " << std::setw(4) << wdl << " (" << s1 << ")"
+ << "\nTablebases DTZ: " << std::setw(4) << dtz << " (" << s2 << ")";
+ }
- for (Bitboard b = pos.checkers(); b; )
- os << UCI::square(pop_lsb(&b)) << " ";
-
- return os;
+ return os;
}
-/// Position::init() initializes at startup the various arrays used to compute
-/// hash keys.
-
-void Position::init() {
+// Implements Marcel van Kervinck's cuckoo algorithm to detect repetition of positions
+// for 3-fold repetition draws. The algorithm uses two hash tables with Zobrist hashes
+// to allow fast detection of recurring positions. For details see:
+// http://web.archive.org/web/20201107002606/https://marcelk.net/2013-04-06/paper/upcoming-rep-v2.pdf
- PRNG rng(1070372);
+// First and second hash functions for indexing the cuckoo tables
+inline int H1(Key h) { return h & 0x1fff; }
+inline int H2(Key h) { return (h >> 16) & 0x1fff; }
- for (Piece pc : Pieces)
- for (Square s = SQ_A1; s <= SQ_H8; ++s)
- Zobrist::psq[pc][s] = rng.rand<Key>();
+// Cuckoo tables with Zobrist hashes of valid reversible moves, and the moves themselves
+Key cuckoo[8192];
+Move cuckooMove[8192];
- for (File f = FILE_A; f <= FILE_H; ++f)
- Zobrist::enpassant[f] = rng.rand<Key>();
- for (int cr = NO_CASTLING; cr <= ANY_CASTLING; ++cr)
- {
- Zobrist::castling[cr] = 0;
- Bitboard b = cr;
- while (b)
- {
- Key k = Zobrist::castling[1ULL << pop_lsb(&b)];
- Zobrist::castling[cr] ^= k ? k : rng.rand<Key>();
- }
- }
+// Initializes at startup the various arrays used to compute hash keys
+void Position::init() {
- Zobrist::side = rng.rand<Key>();
+ PRNG rng(1070372);
+
+ for (Piece pc : Pieces)
+ for (Square s = SQ_A1; s <= SQ_H8; ++s)
+ Zobrist::psq[pc][s] = rng.rand<Key>();
+
+ for (File f = FILE_A; f <= FILE_H; ++f)
+ Zobrist::enpassant[f] = rng.rand<Key>();
+
+ for (int cr = NO_CASTLING; cr <= ANY_CASTLING; ++cr)
+ Zobrist::castling[cr] = rng.rand<Key>();
+
+ Zobrist::side = rng.rand<Key>();
+ Zobrist::noPawns = rng.rand<Key>();
+
+ // Prepare the cuckoo tables
+ std::memset(cuckoo, 0, sizeof(cuckoo));
+ std::memset(cuckooMove, 0, sizeof(cuckooMove));
+ [[maybe_unused]] int count = 0;
+ for (Piece pc : Pieces)
+ for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
+ for (Square s2 = Square(s1 + 1); s2 <= SQ_H8; ++s2)
+ if ((type_of(pc) != PAWN) && (attacks_bb(type_of(pc), s1, 0) & s2))
+ {
+ Move move = make_move(s1, s2);
+ Key key = Zobrist::psq[pc][s1] ^ Zobrist::psq[pc][s2] ^ Zobrist::side;
+ int i = H1(key);
+ while (true)
+ {
+ std::swap(cuckoo[i], key);
+ std::swap(cuckooMove[i], move);
+ if (move == MOVE_NONE) // Arrived at empty slot?
+ break;
+ i = (i == H1(key)) ? H2(key) : H1(key); // Push victim to alternative slot
+ }
+ count++;
+ }
+ assert(count == 3668);
}
-/// Position::set() initializes the position object with the given FEN string.
-/// This function is not very robust - make sure that input FENs are correct,
-/// this is assumed to be the responsibility of the GUI.
-
+// Initializes the position object with the given FEN string.
+// This function is not very robust - make sure that input FENs are correct,
+// this is assumed to be the responsibility of the GUI.
Position& Position::set(const string& fenStr, bool isChess960, StateInfo* si, Thread* th) {
-/*
+ /*
A FEN string defines a particular position using only the ASCII character set.
A FEN string contains six fields separated by a space. The fields are:
4) En passant target square (in algebraic notation). If there's no en passant
target square, this is "-". If a pawn has just made a 2-square move, this
- is the position "behind" the pawn. This is recorded regardless of whether
- there is a pawn in position to make an en passant capture.
+ is the position "behind" the pawn. Following X-FEN standard, this is recorded
+ only if there is a pawn in position to make an en passant capture, and if
+ there really is a pawn that might have advanced two squares.
5) Halfmove clock. This is the number of halfmoves since the last pawn advance
or capture. This is used to determine if a draw can be claimed under the
incremented after Black's move.
*/
- unsigned char col, row, token;
- size_t idx;
- Square sq = SQ_A8;
- std::istringstream ss(fenStr);
-
- std::memset(this, 0, sizeof(Position));
- std::memset(si, 0, sizeof(StateInfo));
- std::fill_n(&pieceList[0][0], sizeof(pieceList) / sizeof(Square), SQ_NONE);
- st = si;
-
- ss >> std::noskipws;
-
- // 1. Piece placement
- while ((ss >> token) && !isspace(token))
- {
- if (isdigit(token))
- sq += Square(token - '0'); // Advance the given number of files
-
- else if (token == '/')
- sq -= Square(16);
-
- else if ((idx = PieceToChar.find(token)) != string::npos)
- {
- put_piece(Piece(idx), sq);
- ++sq;
- }
- }
-
- // 2. Active color
- ss >> token;
- sideToMove = (token == 'w' ? WHITE : BLACK);
- ss >> token;
-
- // 3. Castling availability. Compatible with 3 standards: Normal FEN standard,
- // Shredder-FEN that uses the letters of the columns on which the rooks began
- // the game instead of KQkq and also X-FEN standard that, in case of Chess960,
- // if an inner rook is associated with the castling right, the castling tag is
- // replaced by the file letter of the involved rook, as for the Shredder-FEN.
- while ((ss >> token) && !isspace(token))
- {
- Square rsq;
- Color c = islower(token) ? BLACK : WHITE;
- Piece rook = make_piece(c, ROOK);
-
- token = char(toupper(token));
-
- if (token == 'K')
- for (rsq = relative_square(c, SQ_H1); piece_on(rsq) != rook; --rsq) {}
-
- else if (token == 'Q')
- for (rsq = relative_square(c, SQ_A1); piece_on(rsq) != rook; ++rsq) {}
-
- else if (token >= 'A' && token <= 'H')
- rsq = make_square(File(token - 'A'), relative_rank(c, RANK_1));
-
- else
- continue;
-
- set_castling_right(c, rsq);
- }
-
- // 4. En passant square. Ignore if no pawn capture is possible
- if ( ((ss >> col) && (col >= 'a' && col <= 'h'))
- && ((ss >> row) && (row == '3' || row == '6')))
- {
- st->epSquare = make_square(File(col - 'a'), Rank(row - '1'));
-
- if (!(attackers_to(st->epSquare) & pieces(sideToMove, PAWN)))
- st->epSquare = SQ_NONE;
- }
- else
- st->epSquare = SQ_NONE;
-
- // 5-6. Halfmove clock and fullmove number
- ss >> std::skipws >> st->rule50 >> gamePly;
-
- // Convert from fullmove starting from 1 to ply starting from 0,
- // handle also common incorrect FEN with fullmove = 0.
- gamePly = std::max(2 * (gamePly - 1), 0) + (sideToMove == BLACK);
-
- chess960 = isChess960;
- thisThread = th;
- set_state(st);
-
- assert(pos_is_ok());
-
- return *this;
+ unsigned char col, row, token;
+ size_t idx;
+ Square sq = SQ_A8;
+ std::istringstream ss(fenStr);
+
+ std::memset(this, 0, sizeof(Position));
+ std::memset(si, 0, sizeof(StateInfo));
+ st = si;
+
+ ss >> std::noskipws;
+
+ // 1. Piece placement
+ while ((ss >> token) && !isspace(token))
+ {
+ if (isdigit(token))
+ sq += (token - '0') * EAST; // Advance the given number of files
+
+ else if (token == '/')
+ sq += 2 * SOUTH;
+
+ else if ((idx = PieceToChar.find(token)) != string::npos)
+ {
+ put_piece(Piece(idx), sq);
+ ++sq;
+ }
+ }
+
+ // 2. Active color
+ ss >> token;
+ sideToMove = (token == 'w' ? WHITE : BLACK);
+ ss >> token;
+
+ // 3. Castling availability. Compatible with 3 standards: Normal FEN standard,
+ // Shredder-FEN that uses the letters of the columns on which the rooks began
+ // the game instead of KQkq and also X-FEN standard that, in case of Chess960,
+ // if an inner rook is associated with the castling right, the castling tag is
+ // replaced by the file letter of the involved rook, as for the Shredder-FEN.
+ while ((ss >> token) && !isspace(token))
+ {
+ Square rsq;
+ Color c = islower(token) ? BLACK : WHITE;
+ Piece rook = make_piece(c, ROOK);
+
+ token = char(toupper(token));
+
+ if (token == 'K')
+ for (rsq = relative_square(c, SQ_H1); piece_on(rsq) != rook; --rsq)
+ {}
+
+ else if (token == 'Q')
+ for (rsq = relative_square(c, SQ_A1); piece_on(rsq) != rook; ++rsq)
+ {}
+
+ else if (token >= 'A' && token <= 'H')
+ rsq = make_square(File(token - 'A'), relative_rank(c, RANK_1));
+
+ else
+ continue;
+
+ set_castling_right(c, rsq);
+ }
+
+ // 4. En passant square.
+ // Ignore if square is invalid or not on side to move relative rank 6.
+ bool enpassant = false;
+
+ if (((ss >> col) && (col >= 'a' && col <= 'h'))
+ && ((ss >> row) && (row == (sideToMove == WHITE ? '6' : '3'))))
+ {
+ st->epSquare = make_square(File(col - 'a'), Rank(row - '1'));
+
+ // En passant square will be considered only if
+ // a) side to move have a pawn threatening epSquare
+ // b) there is an enemy pawn in front of epSquare
+ // c) there is no piece on epSquare or behind epSquare
+ enpassant = pawn_attacks_bb(~sideToMove, st->epSquare) & pieces(sideToMove, PAWN)
+ && (pieces(~sideToMove, PAWN) & (st->epSquare + pawn_push(~sideToMove)))
+ && !(pieces() & (st->epSquare | (st->epSquare + pawn_push(sideToMove))));
+ }
+
+ if (!enpassant)
+ st->epSquare = SQ_NONE;
+
+ // 5-6. Halfmove clock and fullmove number
+ ss >> std::skipws >> st->rule50 >> gamePly;
+
+ // Convert from fullmove starting from 1 to gamePly starting from 0,
+ // handle also common incorrect FEN with fullmove = 0.
+ gamePly = std::max(2 * (gamePly - 1), 0) + (sideToMove == BLACK);
+
+ chess960 = isChess960;
+ thisThread = th;
+ set_state();
+
+ assert(pos_is_ok());
+
+ return *this;
}
-/// Position::set_castling_right() is a helper function used to set castling
-/// rights given the corresponding color and the rook starting square.
-
+// Helper function used to set castling
+// rights given the corresponding color and the rook starting square.
void Position::set_castling_right(Color c, Square rfrom) {
- Square kfrom = square<KING>(c);
- CastlingSide cs = kfrom < rfrom ? KING_SIDE : QUEEN_SIDE;
- CastlingRight cr = (c | cs);
+ Square kfrom = square<KING>(c);
+ CastlingRights cr = c & (kfrom < rfrom ? KING_SIDE : QUEEN_SIDE);
- st->castlingRights |= cr;
- castlingRightsMask[kfrom] |= cr;
- castlingRightsMask[rfrom] |= cr;
- castlingRookSquare[cr] = rfrom;
+ st->castlingRights |= cr;
+ castlingRightsMask[kfrom] |= cr;
+ castlingRightsMask[rfrom] |= cr;
+ castlingRookSquare[cr] = rfrom;
- Square kto = relative_square(c, cs == KING_SIDE ? SQ_G1 : SQ_C1);
- Square rto = relative_square(c, cs == KING_SIDE ? SQ_F1 : SQ_D1);
+ Square kto = relative_square(c, cr & KING_SIDE ? SQ_G1 : SQ_C1);
+ Square rto = relative_square(c, cr & KING_SIDE ? SQ_F1 : SQ_D1);
- for (Square s = std::min(rfrom, rto); s <= std::max(rfrom, rto); ++s)
- if (s != kfrom && s != rfrom)
- castlingPath[cr] |= s;
-
- for (Square s = std::min(kfrom, kto); s <= std::max(kfrom, kto); ++s)
- if (s != kfrom && s != rfrom)
- castlingPath[cr] |= s;
+ castlingPath[cr] = (between_bb(rfrom, rto) | between_bb(kfrom, kto)) & ~(kfrom | rfrom);
}
-/// Position::set_check_info() sets king attacks to detect if a move gives check
-
-void Position::set_check_info(StateInfo* si) const {
+// Sets king attacks to detect if a move gives check
+void Position::set_check_info() const {
- si->blockersForKing[WHITE] = slider_blockers(pieces(BLACK), square<KING>(WHITE), si->pinnersForKing[WHITE]);
- si->blockersForKing[BLACK] = slider_blockers(pieces(WHITE), square<KING>(BLACK), si->pinnersForKing[BLACK]);
+ update_slider_blockers(WHITE);
+ update_slider_blockers(BLACK);
- Square ksq = square<KING>(~sideToMove);
+ Square ksq = square<KING>(~sideToMove);
- si->checkSquares[PAWN] = attacks_from<PAWN>(ksq, ~sideToMove);
- si->checkSquares[KNIGHT] = attacks_from<KNIGHT>(ksq);
- si->checkSquares[BISHOP] = attacks_from<BISHOP>(ksq);
- si->checkSquares[ROOK] = attacks_from<ROOK>(ksq);
- si->checkSquares[QUEEN] = si->checkSquares[BISHOP] | si->checkSquares[ROOK];
- si->checkSquares[KING] = 0;
+ st->checkSquares[PAWN] = pawn_attacks_bb(~sideToMove, ksq);
+ st->checkSquares[KNIGHT] = attacks_bb<KNIGHT>(ksq);
+ st->checkSquares[BISHOP] = attacks_bb<BISHOP>(ksq, pieces());
+ st->checkSquares[ROOK] = attacks_bb<ROOK>(ksq, pieces());
+ st->checkSquares[QUEEN] = st->checkSquares[BISHOP] | st->checkSquares[ROOK];
+ st->checkSquares[KING] = 0;
}
-/// Position::set_state() computes the hash keys of the position, and other
-/// data that once computed is updated incrementally as moves are made.
-/// The function is only used when a new position is set up, and to verify
-/// the correctness of the StateInfo data when running in debug mode.
+// Computes the hash keys of the position, and other
+// data that once computed is updated incrementally as moves are made.
+// The function is only used when a new position is set up
+void Position::set_state() const {
-void Position::set_state(StateInfo* si) const {
+ st->key = st->materialKey = 0;
+ st->pawnKey = Zobrist::noPawns;
+ st->nonPawnMaterial[WHITE] = st->nonPawnMaterial[BLACK] = VALUE_ZERO;
+ st->checkersBB = attackers_to(square<KING>(sideToMove)) & pieces(~sideToMove);
- si->key = si->pawnKey = si->materialKey = 0;
- si->nonPawnMaterial[WHITE] = si->nonPawnMaterial[BLACK] = VALUE_ZERO;
- si->psq = SCORE_ZERO;
- si->checkersBB = attackers_to(square<KING>(sideToMove)) & pieces(~sideToMove);
+ set_check_info();
- set_check_info(si);
+ for (Bitboard b = pieces(); b;)
+ {
+ Square s = pop_lsb(b);
+ Piece pc = piece_on(s);
+ st->key ^= Zobrist::psq[pc][s];
- for (Bitboard b = pieces(); b; )
- {
- Square s = pop_lsb(&b);
- Piece pc = piece_on(s);
- si->key ^= Zobrist::psq[pc][s];
- si->psq += PSQT::psq[pc][s];
- }
+ if (type_of(pc) == PAWN)
+ st->pawnKey ^= Zobrist::psq[pc][s];
- if (si->epSquare != SQ_NONE)
- si->key ^= Zobrist::enpassant[file_of(si->epSquare)];
+ else if (type_of(pc) != KING)
+ st->nonPawnMaterial[color_of(pc)] += PieceValue[pc];
+ }
- if (sideToMove == BLACK)
- si->key ^= Zobrist::side;
+ if (st->epSquare != SQ_NONE)
+ st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
- si->key ^= Zobrist::castling[si->castlingRights];
+ if (sideToMove == BLACK)
+ st->key ^= Zobrist::side;
- for (Bitboard b = pieces(PAWN); b; )
- {
- Square s = pop_lsb(&b);
- si->pawnKey ^= Zobrist::psq[piece_on(s)][s];
- }
+ st->key ^= Zobrist::castling[st->castlingRights];
- for (Piece pc : Pieces)
- {
- if (type_of(pc) != PAWN && type_of(pc) != KING)
- si->nonPawnMaterial[color_of(pc)] += pieceCount[pc] * PieceValue[MG][pc];
-
- for (int cnt = 0; cnt < pieceCount[pc]; ++cnt)
- si->materialKey ^= Zobrist::psq[pc][cnt];
- }
+ for (Piece pc : Pieces)
+ for (int cnt = 0; cnt < pieceCount[pc]; ++cnt)
+ st->materialKey ^= Zobrist::psq[pc][cnt];
}
-/// Position::fen() returns a FEN representation of the position. In case of
-/// Chess960 the Shredder-FEN notation is used. This is mainly a debugging function.
-
-const string Position::fen() const {
-
- int emptyCnt;
- std::ostringstream ss;
-
- for (Rank r = RANK_8; r >= RANK_1; --r)
- {
- for (File f = FILE_A; f <= FILE_H; ++f)
- {
- for (emptyCnt = 0; f <= FILE_H && empty(make_square(f, r)); ++f)
- ++emptyCnt;
+// Overload to initialize the position object with the given endgame code string
+// like "KBPKN". It's mainly a helper to get the material key out of an endgame code.
+Position& Position::set(const string& code, Color c, StateInfo* si) {
- if (emptyCnt)
- ss << emptyCnt;
+ assert(code[0] == 'K');
- if (f <= FILE_H)
- ss << PieceToChar[piece_on(make_square(f, r))];
- }
+ string sides[] = {code.substr(code.find('K', 1)), // Weak
+ code.substr(0, std::min(code.find('v'), code.find('K', 1)))}; // Strong
- if (r > RANK_1)
- ss << '/';
- }
+ assert(sides[0].length() > 0 && sides[0].length() < 8);
+ assert(sides[1].length() > 0 && sides[1].length() < 8);
- ss << (sideToMove == WHITE ? " w " : " b ");
+ std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
- if (can_castle(WHITE_OO))
- ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE | KING_SIDE))) : 'K');
+ string fenStr = "8/" + sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/" + sides[1]
+ + char(8 - sides[1].length() + '0') + "/8 w - - 0 10";
- if (can_castle(WHITE_OOO))
- ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE | QUEEN_SIDE))) : 'Q');
-
- if (can_castle(BLACK_OO))
- ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK | KING_SIDE))) : 'k');
-
- if (can_castle(BLACK_OOO))
- ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK | QUEEN_SIDE))) : 'q');
-
- if (!can_castle(WHITE) && !can_castle(BLACK))
- ss << '-';
+ return set(fenStr, false, si, nullptr);
+}
- ss << (ep_square() == SQ_NONE ? " - " : " " + UCI::square(ep_square()) + " ")
- << st->rule50 << " " << 1 + (gamePly - (sideToMove == BLACK)) / 2;
- return ss.str();
-}
+// Returns a FEN representation of the position. In case of
+// Chess960 the Shredder-FEN notation is used. This is mainly a debugging function.
+string Position::fen() const {
+ int emptyCnt;
+ std::ostringstream ss;
-/// Position::game_phase() calculates the game phase interpolating total non-pawn
-/// material between endgame and midgame limits.
+ for (Rank r = RANK_8; r >= RANK_1; --r)
+ {
+ for (File f = FILE_A; f <= FILE_H; ++f)
+ {
+ for (emptyCnt = 0; f <= FILE_H && empty(make_square(f, r)); ++f)
+ ++emptyCnt;
-Phase Position::game_phase() const {
+ if (emptyCnt)
+ ss << emptyCnt;
- Value npm = st->nonPawnMaterial[WHITE] + st->nonPawnMaterial[BLACK];
+ if (f <= FILE_H)
+ ss << PieceToChar[piece_on(make_square(f, r))];
+ }
- npm = std::max(EndgameLimit, std::min(npm, MidgameLimit));
+ if (r > RANK_1)
+ ss << '/';
+ }
- return Phase(((npm - EndgameLimit) * PHASE_MIDGAME) / (MidgameLimit - EndgameLimit));
-}
+ ss << (sideToMove == WHITE ? " w " : " b ");
+ if (can_castle(WHITE_OO))
+ ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE_OO))) : 'K');
-/// Position::slider_blockers() returns a bitboard of all the pieces (both colors)
-/// that are blocking attacks on the square 's' from 'sliders'. A piece blocks a
-/// slider if removing that piece from the board would result in a position where
-/// square 's' is attacked. For example, a king-attack blocking piece can be either
-/// a pinned or a discovered check piece, according if its color is the opposite
-/// or the same of the color of the slider. The pinners bitboard get filled with
-/// real and potential pinners.
+ if (can_castle(WHITE_OOO))
+ ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE_OOO))) : 'Q');
-Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const {
+ if (can_castle(BLACK_OO))
+ ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK_OO))) : 'k');
- Bitboard b, p, result = 0;
+ if (can_castle(BLACK_OOO))
+ ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK_OOO))) : 'q');
- // Pinners are sliders that attack 's' when a pinned piece is removed
- pinners = p = ( (PseudoAttacks[ROOK ][s] & pieces(QUEEN, ROOK))
- | (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders;
+ if (!can_castle(ANY_CASTLING))
+ ss << '-';
- while (p)
- {
- b = between_bb(s, pop_lsb(&p)) & pieces();
+ ss << (ep_square() == SQ_NONE ? " - " : " " + UCI::square(ep_square()) + " ") << st->rule50
+ << " " << 1 + (gamePly - (sideToMove == BLACK)) / 2;
- if (!more_than_one(b))
- result |= b;
- }
- return result;
+ return ss.str();
}
+// Calculates st->blockersForKing[c] and st->pinners[~c],
+// which store respectively the pieces preventing king of color c from being in check
+// and the slider pieces of color ~c pinning pieces of color c to the king.
+void Position::update_slider_blockers(Color c) const {
+
+ Square ksq = square<KING>(c);
+
+ st->blockersForKing[c] = 0;
+ st->pinners[~c] = 0;
+
+ // Snipers are sliders that attack 's' when a piece and other snipers are removed
+ Bitboard snipers = ((attacks_bb<ROOK>(ksq) & pieces(QUEEN, ROOK))
+ | (attacks_bb<BISHOP>(ksq) & pieces(QUEEN, BISHOP)))
+ & pieces(~c);
+ Bitboard occupancy = pieces() ^ snipers;
+
+ while (snipers)
+ {
+ Square sniperSq = pop_lsb(snipers);
+ Bitboard b = between_bb(ksq, sniperSq) & occupancy;
+
+ if (b && !more_than_one(b))
+ {
+ st->blockersForKing[c] |= b;
+ if (b & pieces(c))
+ st->pinners[~c] |= sniperSq;
+ }
+ }
+}
-/// Position::attackers_to() computes a bitboard of all pieces which attack a
-/// given square. Slider attacks use the occupied bitboard to indicate occupancy.
+// Computes a bitboard of all pieces which attack a given square.
+// Slider attacks use the occupied bitboard to indicate occupancy.
Bitboard Position::attackers_to(Square s, Bitboard occupied) const {
- return (attacks_from<PAWN>(s, BLACK) & pieces(WHITE, PAWN))
- | (attacks_from<PAWN>(s, WHITE) & pieces(BLACK, PAWN))
- | (attacks_from<KNIGHT>(s) & pieces(KNIGHT))
- | (attacks_bb<ROOK >(s, occupied) & pieces(ROOK, QUEEN))
- | (attacks_bb<BISHOP>(s, occupied) & pieces(BISHOP, QUEEN))
- | (attacks_from<KING>(s) & pieces(KING));
+ return (pawn_attacks_bb(BLACK, s) & pieces(WHITE, PAWN))
+ | (pawn_attacks_bb(WHITE, s) & pieces(BLACK, PAWN))
+ | (attacks_bb<KNIGHT>(s) & pieces(KNIGHT))
+ | (attacks_bb<ROOK>(s, occupied) & pieces(ROOK, QUEEN))
+ | (attacks_bb<BISHOP>(s, occupied) & pieces(BISHOP, QUEEN))
+ | (attacks_bb<KING>(s) & pieces(KING));
}
-/// Position::legal() tests whether a pseudo-legal move is legal
-
+// Tests whether a pseudo-legal move is legal
bool Position::legal(Move m) const {
- assert(is_ok(m));
+ assert(is_ok(m));
- Color us = sideToMove;
- Square from = from_sq(m);
+ Color us = sideToMove;
+ Square from = from_sq(m);
+ Square to = to_sq(m);
- assert(color_of(moved_piece(m)) == us);
- assert(piece_on(square<KING>(us)) == make_piece(us, KING));
+ assert(color_of(moved_piece(m)) == us);
+ assert(piece_on(square<KING>(us)) == make_piece(us, KING));
- // En passant captures are a tricky special case. Because they are rather
- // uncommon, we do it simply by testing whether the king is attacked after
- // the move is made.
- if (type_of(m) == ENPASSANT)
- {
- Square ksq = square<KING>(us);
- Square to = to_sq(m);
- Square capsq = to - pawn_push(us);
- Bitboard occupied = (pieces() ^ from ^ capsq) | to;
+ // En passant captures are a tricky special case. Because they are rather
+ // uncommon, we do it simply by testing whether the king is attacked after
+ // the move is made.
+ if (type_of(m) == EN_PASSANT)
+ {
+ Square ksq = square<KING>(us);
+ Square capsq = to - pawn_push(us);
+ Bitboard occupied = (pieces() ^ from ^ capsq) | to;
- assert(to == ep_square());
- assert(moved_piece(m) == make_piece(us, PAWN));
- assert(piece_on(capsq) == make_piece(~us, PAWN));
- assert(piece_on(to) == NO_PIECE);
+ assert(to == ep_square());
+ assert(moved_piece(m) == make_piece(us, PAWN));
+ assert(piece_on(capsq) == make_piece(~us, PAWN));
+ assert(piece_on(to) == NO_PIECE);
- return !(attacks_bb< ROOK>(ksq, occupied) & pieces(~us, QUEEN, ROOK))
+ return !(attacks_bb<ROOK>(ksq, occupied) & pieces(~us, QUEEN, ROOK))
&& !(attacks_bb<BISHOP>(ksq, occupied) & pieces(~us, QUEEN, BISHOP));
- }
-
- // If the moving piece is a king, check whether the destination
- // square is attacked by the opponent. Castling moves are checked
- // for legality during move generation.
- if (type_of(piece_on(from)) == KING)
- return type_of(m) == CASTLING || !(attackers_to(to_sq(m)) & pieces(~us));
-
- // A non-king move is legal if and only if it is not pinned or it
- // is moving along the ray towards or away from the king.
- return !(pinned_pieces(us) & from)
- || aligned(from, to_sq(m), square<KING>(us));
+ }
+
+ // Castling moves generation does not check if the castling path is clear of
+ // enemy attacks, it is delayed at a later time: now!
+ if (type_of(m) == CASTLING)
+ {
+ // After castling, the rook and king final positions are the same in
+ // Chess960 as they would be in standard chess.
+ to = relative_square(us, to > from ? SQ_G1 : SQ_C1);
+ Direction step = to > from ? WEST : EAST;
+
+ for (Square s = to; s != from; s += step)
+ if (attackers_to(s) & pieces(~us))
+ return false;
+
+ // In case of Chess960, verify if the Rook blocks some checks.
+ // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
+ return !chess960 || !(blockers_for_king(us) & to_sq(m));
+ }
+
+ // If the moving piece is a king, check whether the destination square is
+ // attacked by the opponent.
+ if (type_of(piece_on(from)) == KING)
+ return !(attackers_to(to, pieces() ^ from) & pieces(~us));
+
+ // A non-king move is legal if and only if it is not pinned or it
+ // is moving along the ray towards or away from the king.
+ return !(blockers_for_king(us) & from) || aligned(from, to, square<KING>(us));
}
-/// Position::pseudo_legal() takes a random move and tests whether the move is
-/// pseudo legal. It is used to validate moves from TT that can be corrupted
-/// due to SMP concurrent access or hash position key aliasing.
-
+// Takes a random move and tests whether the move is
+// pseudo-legal. It is used to validate moves from TT that can be corrupted
+// due to SMP concurrent access or hash position key aliasing.
bool Position::pseudo_legal(const Move m) const {
- Color us = sideToMove;
- Square from = from_sq(m);
- Square to = to_sq(m);
- Piece pc = moved_piece(m);
-
- // Use a slower but simpler function for uncommon cases
- if (type_of(m) != NORMAL)
- return MoveList<LEGAL>(*this).contains(m);
-
- // Is not a promotion, so promotion piece must be empty
- if (promotion_type(m) - KNIGHT != NO_PIECE_TYPE)
- return false;
-
- // If the 'from' square is not occupied by a piece belonging to the side to
- // move, the move is obviously not legal.
- if (pc == NO_PIECE || color_of(pc) != us)
- return false;
-
- // The destination square cannot be occupied by a friendly piece
- if (pieces(us) & to)
- return false;
-
- // Handle the special case of a pawn move
- if (type_of(pc) == PAWN)
- {
- // We have already handled promotion moves, so destination
- // cannot be on the 8th/1st rank.
- if (rank_of(to) == relative_rank(us, RANK_8))
- return false;
-
- if ( !(attacks_from<PAWN>(from, us) & pieces(~us) & to) // Not a capture
- && !((from + pawn_push(us) == to) && empty(to)) // Not a single push
- && !( (from + 2 * pawn_push(us) == to) // Not a double push
- && (rank_of(from) == relative_rank(us, RANK_2))
- && empty(to)
- && empty(to - pawn_push(us))))
- return false;
- }
- else if (!(attacks_from(pc, from) & to))
- return false;
-
- // Evasions generator already takes care to avoid some kind of illegal moves
- // and legal() relies on this. We therefore have to take care that the same
- // kind of moves are filtered out here.
- if (checkers())
- {
- if (type_of(pc) != KING)
- {
- // Double check? In this case a king move is required
- if (more_than_one(checkers()))
- return false;
-
- // Our move must be a blocking evasion or a capture of the checking piece
- if (!((between_bb(lsb(checkers()), square<KING>(us)) | checkers()) & to))
- return false;
- }
- // In case of king moves under check we have to remove king so as to catch
- // invalid moves like b1a1 when opposite queen is on c1.
- else if (attackers_to(to, pieces() ^ from) & pieces(~us))
- return false;
- }
-
- return true;
+ Color us = sideToMove;
+ Square from = from_sq(m);
+ Square to = to_sq(m);
+ Piece pc = moved_piece(m);
+
+ // Use a slower but simpler function for uncommon cases
+ // yet we skip the legality check of MoveList<LEGAL>().
+ if (type_of(m) != NORMAL)
+ return checkers() ? MoveList<EVASIONS>(*this).contains(m)
+ : MoveList<NON_EVASIONS>(*this).contains(m);
+
+ // Is not a promotion, so the promotion piece must be empty
+ assert(promotion_type(m) - KNIGHT == NO_PIECE_TYPE);
+
+ // If the 'from' square is not occupied by a piece belonging to the side to
+ // move, the move is obviously not legal.
+ if (pc == NO_PIECE || color_of(pc) != us)
+ return false;
+
+ // The destination square cannot be occupied by a friendly piece
+ if (pieces(us) & to)
+ return false;
+
+ // Handle the special case of a pawn move
+ if (type_of(pc) == PAWN)
+ {
+ // We have already handled promotion moves, so destination cannot be on the 8th/1st rank
+ if ((Rank8BB | Rank1BB) & to)
+ return false;
+
+ if (!(pawn_attacks_bb(us, from) & pieces(~us) & to) // Not a capture
+ && !((from + pawn_push(us) == to) && empty(to)) // Not a single push
+ && !((from + 2 * pawn_push(us) == to) // Not a double push
+ && (relative_rank(us, from) == RANK_2) && empty(to) && empty(to - pawn_push(us))))
+ return false;
+ }
+ else if (!(attacks_bb(type_of(pc), from, pieces()) & to))
+ return false;
+
+ // Evasions generator already takes care to avoid some kind of illegal moves
+ // and legal() relies on this. We therefore have to take care that the same
+ // kind of moves are filtered out here.
+ if (checkers())
+ {
+ if (type_of(pc) != KING)
+ {
+ // Double check? In this case, a king move is required
+ if (more_than_one(checkers()))
+ return false;
+
+ // Our move must be a blocking interposition or a capture of the checking piece
+ if (!(between_bb(square<KING>(us), lsb(checkers())) & to))
+ return false;
+ }
+ // In case of king moves under check we have to remove the king so as to catch
+ // invalid moves like b1a1 when opposite queen is on c1.
+ else if (attackers_to(to, pieces() ^ from) & pieces(~us))
+ return false;
+ }
+
+ return true;
}
-/// Position::gives_check() tests whether a pseudo-legal move gives a check
-
+// Tests whether a pseudo-legal move gives a check
bool Position::gives_check(Move m) const {
- assert(is_ok(m));
- assert(color_of(moved_piece(m)) == sideToMove);
-
- Square from = from_sq(m);
- Square to = to_sq(m);
-
- // Is there a direct check?
- if (st->checkSquares[type_of(piece_on(from))] & to)
- return true;
-
- // Is there a discovered check?
- if ( (discovered_check_candidates() & from)
- && !aligned(from, to, square<KING>(~sideToMove)))
- return true;
-
- switch (type_of(m))
- {
- case NORMAL:
- return false;
-
- case PROMOTION:
- return attacks_bb(Piece(promotion_type(m)), to, pieces() ^ from) & square<KING>(~sideToMove);
-
- // En passant capture with check? We have already handled the case
- // of direct checks and ordinary discovered check, so the only case we
- // need to handle is the unusual case of a discovered check through
- // the captured pawn.
- case ENPASSANT:
- {
- Square capsq = make_square(file_of(to), rank_of(from));
- Bitboard b = (pieces() ^ from ^ capsq) | to;
-
- return (attacks_bb< ROOK>(square<KING>(~sideToMove), b) & pieces(sideToMove, QUEEN, ROOK))
- | (attacks_bb<BISHOP>(square<KING>(~sideToMove), b) & pieces(sideToMove, QUEEN, BISHOP));
- }
- case CASTLING:
- {
- Square kfrom = from;
- Square rfrom = to; // Castling is encoded as 'King captures the rook'
- Square kto = relative_square(sideToMove, rfrom > kfrom ? SQ_G1 : SQ_C1);
- Square rto = relative_square(sideToMove, rfrom > kfrom ? SQ_F1 : SQ_D1);
-
- return (PseudoAttacks[ROOK][rto] & square<KING>(~sideToMove))
- && (attacks_bb<ROOK>(rto, (pieces() ^ kfrom ^ rfrom) | rto | kto) & square<KING>(~sideToMove));
- }
- default:
- assert(false);
- return false;
- }
+ assert(is_ok(m));
+ assert(color_of(moved_piece(m)) == sideToMove);
+
+ Square from = from_sq(m);
+ Square to = to_sq(m);
+
+ // Is there a direct check?
+ if (check_squares(type_of(piece_on(from))) & to)
+ return true;
+
+ // Is there a discovered check?
+ if (blockers_for_king(~sideToMove) & from)
+ return !aligned(from, to, square<KING>(~sideToMove)) || type_of(m) == CASTLING;
+
+ switch (type_of(m))
+ {
+ case NORMAL :
+ return false;
+
+ case PROMOTION :
+ return attacks_bb(promotion_type(m), to, pieces() ^ from) & square<KING>(~sideToMove);
+
+ // En passant capture with check? We have already handled the case of direct
+ // checks and ordinary discovered check, so the only case we need to handle
+ // is the unusual case of a discovered check through the captured pawn.
+ case EN_PASSANT : {
+ Square capsq = make_square(file_of(to), rank_of(from));
+ Bitboard b = (pieces() ^ from ^ capsq) | to;
+
+ return (attacks_bb<ROOK>(square<KING>(~sideToMove), b) & pieces(sideToMove, QUEEN, ROOK))
+ | (attacks_bb<BISHOP>(square<KING>(~sideToMove), b)
+ & pieces(sideToMove, QUEEN, BISHOP));
+ }
+ default : //CASTLING
+ {
+ // Castling is encoded as 'king captures the rook'
+ Square rto = relative_square(sideToMove, to > from ? SQ_F1 : SQ_D1);
+
+ return check_squares(ROOK) & rto;
+ }
+ }
}
-/// Position::do_move() makes a move, and saves all information necessary
-/// to a StateInfo object. The move is assumed to be legal. Pseudo-legal
-/// moves should be filtered out before this function is called.
-
+// Makes a move, and saves all information necessary
+// to a StateInfo object. The move is assumed to be legal. Pseudo-legal
+// moves should be filtered out before this function is called.
void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
- assert(is_ok(m));
- assert(&newSt != st);
-
- ++nodes;
- Key k = st->key ^ Zobrist::side;
-
- // Copy some fields of the old state to our new StateInfo object except the
- // ones which are going to be recalculated from scratch anyway and then switch
- // our state pointer to point to the new (ready to be updated) state.
- std::memcpy(&newSt, st, offsetof(StateInfo, key));
- newSt.previous = st;
- st = &newSt;
-
- // Increment ply counters. In particular, rule50 will be reset to zero later on
- // in case of a capture or a pawn move.
- ++gamePly;
- ++st->rule50;
- ++st->pliesFromNull;
-
- Color us = sideToMove;
- Color them = ~us;
- Square from = from_sq(m);
- Square to = to_sq(m);
- Piece pc = piece_on(from);
- Piece captured = type_of(m) == ENPASSANT ? make_piece(them, PAWN) : piece_on(to);
-
- assert(color_of(pc) == us);
- assert(captured == NO_PIECE || color_of(captured) == (type_of(m) != CASTLING ? them : us));
- assert(type_of(captured) != KING);
-
- if (type_of(m) == CASTLING)
- {
- assert(pc == make_piece(us, KING));
- assert(captured == make_piece(us, ROOK));
-
- Square rfrom, rto;
- do_castling<true>(us, from, to, rfrom, rto);
-
- st->psq += PSQT::psq[captured][rto] - PSQT::psq[captured][rfrom];
- k ^= Zobrist::psq[captured][rfrom] ^ Zobrist::psq[captured][rto];
- captured = NO_PIECE;
- }
-
- if (captured)
- {
- Square capsq = to;
-
- // If the captured piece is a pawn, update pawn hash key, otherwise
- // update non-pawn material.
- if (type_of(captured) == PAWN)
- {
- if (type_of(m) == ENPASSANT)
- {
- capsq -= pawn_push(us);
-
- assert(pc == make_piece(us, PAWN));
- assert(to == st->epSquare);
- assert(relative_rank(us, to) == RANK_6);
- assert(piece_on(to) == NO_PIECE);
- assert(piece_on(capsq) == make_piece(them, PAWN));
-
- board[capsq] = NO_PIECE; // Not done by remove_piece()
- }
-
- st->pawnKey ^= Zobrist::psq[captured][capsq];
- }
- else
- st->nonPawnMaterial[them] -= PieceValue[MG][captured];
-
- // Update board and piece lists
- remove_piece(captured, capsq);
-
- // Update material hash key and prefetch access to materialTable
- k ^= Zobrist::psq[captured][capsq];
- st->materialKey ^= Zobrist::psq[captured][pieceCount[captured]];
- prefetch(thisThread->materialTable[st->materialKey]);
-
- // Update incremental scores
- st->psq -= PSQT::psq[captured][capsq];
-
- // Reset rule 50 counter
- st->rule50 = 0;
- }
-
- // Update hash key
- k ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
-
- // Reset en passant square
- if (st->epSquare != SQ_NONE)
- {
- k ^= Zobrist::enpassant[file_of(st->epSquare)];
- st->epSquare = SQ_NONE;
- }
-
- // Update castling rights if needed
- if (st->castlingRights && (castlingRightsMask[from] | castlingRightsMask[to]))
- {
- int cr = castlingRightsMask[from] | castlingRightsMask[to];
- k ^= Zobrist::castling[st->castlingRights & cr];
- st->castlingRights &= ~cr;
- }
-
- // Move the piece. The tricky Chess960 castling is handled earlier
- if (type_of(m) != CASTLING)
- move_piece(pc, from, to);
-
- // If the moving piece is a pawn do some special extra work
- if (type_of(pc) == PAWN)
- {
- // Set en-passant square if the moved pawn can be captured
- if ( (int(to) ^ int(from)) == 16
- && (attacks_from<PAWN>(to - pawn_push(us), us) & pieces(them, PAWN)))
- {
- st->epSquare = (from + to) / 2;
- k ^= Zobrist::enpassant[file_of(st->epSquare)];
- }
-
- else if (type_of(m) == PROMOTION)
- {
- Piece promotion = make_piece(us, promotion_type(m));
-
- assert(relative_rank(us, to) == RANK_8);
- assert(type_of(promotion) >= KNIGHT && type_of(promotion) <= QUEEN);
-
- remove_piece(pc, to);
- put_piece(promotion, to);
-
- // Update hash keys
- k ^= Zobrist::psq[pc][to] ^ Zobrist::psq[promotion][to];
- st->pawnKey ^= Zobrist::psq[pc][to];
- st->materialKey ^= Zobrist::psq[promotion][pieceCount[promotion]-1]
- ^ Zobrist::psq[pc][pieceCount[pc]];
-
- // Update incremental score
- st->psq += PSQT::psq[promotion][to] - PSQT::psq[pc][to];
-
- // Update material
- st->nonPawnMaterial[us] += PieceValue[MG][promotion];
- }
-
- // Update pawn hash key and prefetch access to pawnsTable
- st->pawnKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
- prefetch(thisThread->pawnsTable[st->pawnKey]);
-
- // Reset rule 50 draw counter
- st->rule50 = 0;
- }
-
- // Update incremental scores
- st->psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
-
- // Set capture piece
- st->capturedPiece = captured;
-
- // Update the key with the final value
- st->key = k;
-
- // Calculate checkers bitboard (if move gives check)
- st->checkersBB = givesCheck ? attackers_to(square<KING>(them)) & pieces(us) : 0;
-
- sideToMove = ~sideToMove;
-
- // Update king attacks used for fast check detection
- set_check_info(st);
-
- assert(pos_is_ok());
+ assert(is_ok(m));
+ assert(&newSt != st);
+
+ thisThread->nodes.fetch_add(1, std::memory_order_relaxed);
+ Key k = st->key ^ Zobrist::side;
+
+ // Copy some fields of the old state to our new StateInfo object except the
+ // ones which are going to be recalculated from scratch anyway and then switch
+ // our state pointer to point to the new (ready to be updated) state.
+ std::memcpy(&newSt, st, offsetof(StateInfo, key));
+ newSt.previous = st;
+ st = &newSt;
+
+ // Increment ply counters. In particular, rule50 will be reset to zero later on
+ // in case of a capture or a pawn move.
+ ++gamePly;
+ ++st->rule50;
+ ++st->pliesFromNull;
+
+ // Used by NNUE
+ st->accumulator.computed[WHITE] = false;
+ st->accumulator.computed[BLACK] = false;
+ auto& dp = st->dirtyPiece;
+ dp.dirty_num = 1;
+
+ Color us = sideToMove;
+ Color them = ~us;
+ Square from = from_sq(m);
+ Square to = to_sq(m);
+ Piece pc = piece_on(from);
+ Piece captured = type_of(m) == EN_PASSANT ? make_piece(them, PAWN) : piece_on(to);
+
+ assert(color_of(pc) == us);
+ assert(captured == NO_PIECE || color_of(captured) == (type_of(m) != CASTLING ? them : us));
+ assert(type_of(captured) != KING);
+
+ if (type_of(m) == CASTLING)
+ {
+ assert(pc == make_piece(us, KING));
+ assert(captured == make_piece(us, ROOK));
+
+ Square rfrom, rto;
+ do_castling<true>(us, from, to, rfrom, rto);
+
+ k ^= Zobrist::psq[captured][rfrom] ^ Zobrist::psq[captured][rto];
+ captured = NO_PIECE;
+ }
+
+ if (captured)
+ {
+ Square capsq = to;
+
+ // If the captured piece is a pawn, update pawn hash key, otherwise
+ // update non-pawn material.
+ if (type_of(captured) == PAWN)
+ {
+ if (type_of(m) == EN_PASSANT)
+ {
+ capsq -= pawn_push(us);
+
+ assert(pc == make_piece(us, PAWN));
+ assert(to == st->epSquare);
+ assert(relative_rank(us, to) == RANK_6);
+ assert(piece_on(to) == NO_PIECE);
+ assert(piece_on(capsq) == make_piece(them, PAWN));
+ }
+
+ st->pawnKey ^= Zobrist::psq[captured][capsq];
+ }
+ else
+ st->nonPawnMaterial[them] -= PieceValue[captured];
+
+ dp.dirty_num = 2; // 1 piece moved, 1 piece captured
+ dp.piece[1] = captured;
+ dp.from[1] = capsq;
+ dp.to[1] = SQ_NONE;
+
+ // Update board and piece lists
+ remove_piece(capsq);
+
+ // Update material hash key and prefetch access to materialTable
+ k ^= Zobrist::psq[captured][capsq];
+ st->materialKey ^= Zobrist::psq[captured][pieceCount[captured]];
+
+ // Reset rule 50 counter
+ st->rule50 = 0;
+ }
+
+ // Update hash key
+ k ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
+
+ // Reset en passant square
+ if (st->epSquare != SQ_NONE)
+ {
+ k ^= Zobrist::enpassant[file_of(st->epSquare)];
+ st->epSquare = SQ_NONE;
+ }
+
+ // Update castling rights if needed
+ if (st->castlingRights && (castlingRightsMask[from] | castlingRightsMask[to]))
+ {
+ k ^= Zobrist::castling[st->castlingRights];
+ st->castlingRights &= ~(castlingRightsMask[from] | castlingRightsMask[to]);
+ k ^= Zobrist::castling[st->castlingRights];
+ }
+
+ // Move the piece. The tricky Chess960 castling is handled earlier
+ if (type_of(m) != CASTLING)
+ {
+ dp.piece[0] = pc;
+ dp.from[0] = from;
+ dp.to[0] = to;
+
+ move_piece(from, to);
+ }
+
+ // If the moving piece is a pawn do some special extra work
+ if (type_of(pc) == PAWN)
+ {
+ // Set en passant square if the moved pawn can be captured
+ if ((int(to) ^ int(from)) == 16
+ && (pawn_attacks_bb(us, to - pawn_push(us)) & pieces(them, PAWN)))
+ {
+ st->epSquare = to - pawn_push(us);
+ k ^= Zobrist::enpassant[file_of(st->epSquare)];
+ }
+
+ else if (type_of(m) == PROMOTION)
+ {
+ Piece promotion = make_piece(us, promotion_type(m));
+
+ assert(relative_rank(us, to) == RANK_8);
+ assert(type_of(promotion) >= KNIGHT && type_of(promotion) <= QUEEN);
+
+ remove_piece(to);
+ put_piece(promotion, to);
+
+ // Promoting pawn to SQ_NONE, promoted piece from SQ_NONE
+ dp.to[0] = SQ_NONE;
+ dp.piece[dp.dirty_num] = promotion;
+ dp.from[dp.dirty_num] = SQ_NONE;
+ dp.to[dp.dirty_num] = to;
+ dp.dirty_num++;
+
+ // Update hash keys
+ k ^= Zobrist::psq[pc][to] ^ Zobrist::psq[promotion][to];
+ st->pawnKey ^= Zobrist::psq[pc][to];
+ st->materialKey ^=
+ Zobrist::psq[promotion][pieceCount[promotion] - 1] ^ Zobrist::psq[pc][pieceCount[pc]];
+
+ // Update material
+ st->nonPawnMaterial[us] += PieceValue[promotion];
+ }
+
+ // Update pawn hash key
+ st->pawnKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
+
+ // Reset rule 50 draw counter
+ st->rule50 = 0;
+ }
+
+ // Set capture piece
+ st->capturedPiece = captured;
+
+ // Update the key with the final value
+ st->key = k;
+
+ // Calculate checkers bitboard (if move gives check)
+ st->checkersBB = givesCheck ? attackers_to(square<KING>(them)) & pieces(us) : 0;
+
+ sideToMove = ~sideToMove;
+
+ // Update king attacks used for fast check detection
+ set_check_info();
+
+ // Calculate the repetition info. It is the ply distance from the previous
+ // occurrence of the same position, negative in the 3-fold case, or zero
+ // if the position was not repeated.
+ st->repetition = 0;
+ int end = std::min(st->rule50, st->pliesFromNull);
+ if (end >= 4)
+ {
+ StateInfo* stp = st->previous->previous;
+ for (int i = 4; i <= end; i += 2)
+ {
+ stp = stp->previous->previous;
+ if (stp->key == st->key)
+ {
+ st->repetition = stp->repetition ? -i : i;
+ break;
+ }
+ }
+ }
+
+ assert(pos_is_ok());
}
-/// Position::undo_move() unmakes a move. When it returns, the position should
-/// be restored to exactly the same state as before the move was made.
-
+// Unmakes a move. When it returns, the position should
+// be restored to exactly the same state as before the move was made.
void Position::undo_move(Move m) {
- assert(is_ok(m));
-
- sideToMove = ~sideToMove;
-
- Color us = sideToMove;
- Square from = from_sq(m);
- Square to = to_sq(m);
- Piece pc = piece_on(to);
-
- assert(empty(from) || type_of(m) == CASTLING);
- assert(type_of(st->capturedPiece) != KING);
-
- if (type_of(m) == PROMOTION)
- {
- assert(relative_rank(us, to) == RANK_8);
- assert(type_of(pc) == promotion_type(m));
- assert(type_of(pc) >= KNIGHT && type_of(pc) <= QUEEN);
-
- remove_piece(pc, to);
- pc = make_piece(us, PAWN);
- put_piece(pc, to);
- }
-
- if (type_of(m) == CASTLING)
- {
- Square rfrom, rto;
- do_castling<false>(us, from, to, rfrom, rto);
- }
- else
- {
- move_piece(pc, to, from); // Put the piece back at the source square
-
- if (st->capturedPiece)
- {
- Square capsq = to;
-
- if (type_of(m) == ENPASSANT)
- {
- capsq -= pawn_push(us);
-
- assert(type_of(pc) == PAWN);
- assert(to == st->previous->epSquare);
- assert(relative_rank(us, to) == RANK_6);
- assert(piece_on(capsq) == NO_PIECE);
- assert(st->capturedPiece == make_piece(~us, PAWN));
- }
-
- put_piece(st->capturedPiece, capsq); // Restore the captured piece
- }
- }
-
- // Finally point our state pointer back to the previous state
- st = st->previous;
- --gamePly;
-
- assert(pos_is_ok());
+ assert(is_ok(m));
+
+ sideToMove = ~sideToMove;
+
+ Color us = sideToMove;
+ Square from = from_sq(m);
+ Square to = to_sq(m);
+ Piece pc = piece_on(to);
+
+ assert(empty(from) || type_of(m) == CASTLING);
+ assert(type_of(st->capturedPiece) != KING);
+
+ if (type_of(m) == PROMOTION)
+ {
+ assert(relative_rank(us, to) == RANK_8);
+ assert(type_of(pc) == promotion_type(m));
+ assert(type_of(pc) >= KNIGHT && type_of(pc) <= QUEEN);
+
+ remove_piece(to);
+ pc = make_piece(us, PAWN);
+ put_piece(pc, to);
+ }
+
+ if (type_of(m) == CASTLING)
+ {
+ Square rfrom, rto;
+ do_castling<false>(us, from, to, rfrom, rto);
+ }
+ else
+ {
+ move_piece(to, from); // Put the piece back at the source square
+
+ if (st->capturedPiece)
+ {
+ Square capsq = to;
+
+ if (type_of(m) == EN_PASSANT)
+ {
+ capsq -= pawn_push(us);
+
+ assert(type_of(pc) == PAWN);
+ assert(to == st->previous->epSquare);
+ assert(relative_rank(us, to) == RANK_6);
+ assert(piece_on(capsq) == NO_PIECE);
+ assert(st->capturedPiece == make_piece(~us, PAWN));
+ }
+
+ put_piece(st->capturedPiece, capsq); // Restore the captured piece
+ }
+ }
+
+ // Finally point our state pointer back to the previous state
+ st = st->previous;
+ --gamePly;
+
+ assert(pos_is_ok());
}
-/// Position::do_castling() is a helper used to do/undo a castling move. This
-/// is a bit tricky in Chess960 where from/to squares can overlap.
+// Helper used to do/undo a castling move. This is a bit
+// tricky in Chess960 where from/to squares can overlap.
template<bool Do>
void Position::do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto) {
- bool kingSide = to > from;
- rfrom = to; // Castling is encoded as "king captures friendly rook"
- rto = relative_square(us, kingSide ? SQ_F1 : SQ_D1);
- to = relative_square(us, kingSide ? SQ_G1 : SQ_C1);
-
- // Remove both pieces first since squares could overlap in Chess960
- remove_piece(make_piece(us, KING), Do ? from : to);
- remove_piece(make_piece(us, ROOK), Do ? rfrom : rto);
- board[Do ? from : to] = board[Do ? rfrom : rto] = NO_PIECE; // Since remove_piece doesn't do it for us
- put_piece(make_piece(us, KING), Do ? to : from);
- put_piece(make_piece(us, ROOK), Do ? rto : rfrom);
+ bool kingSide = to > from;
+ rfrom = to; // Castling is encoded as "king captures friendly rook"
+ rto = relative_square(us, kingSide ? SQ_F1 : SQ_D1);
+ to = relative_square(us, kingSide ? SQ_G1 : SQ_C1);
+
+ if (Do)
+ {
+ auto& dp = st->dirtyPiece;
+ dp.piece[0] = make_piece(us, KING);
+ dp.from[0] = from;
+ dp.to[0] = to;
+ dp.piece[1] = make_piece(us, ROOK);
+ dp.from[1] = rfrom;
+ dp.to[1] = rto;
+ dp.dirty_num = 2;
+ }
+
+ // Remove both pieces first since squares could overlap in Chess960
+ remove_piece(Do ? from : to);
+ remove_piece(Do ? rfrom : rto);
+ board[Do ? from : to] = board[Do ? rfrom : rto] =
+ NO_PIECE; // remove_piece does not do this for us
+ put_piece(make_piece(us, KING), Do ? to : from);
+ put_piece(make_piece(us, ROOK), Do ? rto : rfrom);
}
-/// Position::do(undo)_null_move() is used to do(undo) a "null move": It flips
-/// the side to move without executing any move on the board.
-
+// Used to do a "null move": it flips
+// the side to move without executing any move on the board.
void Position::do_null_move(StateInfo& newSt) {
- assert(!checkers());
- assert(&newSt != st);
+ assert(!checkers());
+ assert(&newSt != st);
+
+ std::memcpy(&newSt, st, offsetof(StateInfo, accumulator));
+
+ newSt.previous = st;
+ st = &newSt;
+
+ st->dirtyPiece.dirty_num = 0;
+ st->dirtyPiece.piece[0] = NO_PIECE; // Avoid checks in UpdateAccumulator()
+ st->accumulator.computed[WHITE] = false;
+ st->accumulator.computed[BLACK] = false;
- std::memcpy(&newSt, st, sizeof(StateInfo));
- newSt.previous = st;
- st = &newSt;
+ if (st->epSquare != SQ_NONE)
+ {
+ st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
+ st->epSquare = SQ_NONE;
+ }
- if (st->epSquare != SQ_NONE)
- {
- st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
- st->epSquare = SQ_NONE;
- }
+ st->key ^= Zobrist::side;
+ ++st->rule50;
+ prefetch(TT.first_entry(key()));
- st->key ^= Zobrist::side;
- prefetch(TT.first_entry(st->key));
+ st->pliesFromNull = 0;
- ++st->rule50;
- st->pliesFromNull = 0;
+ sideToMove = ~sideToMove;
- sideToMove = ~sideToMove;
+ set_check_info();
- set_check_info(st);
+ st->repetition = 0;
- assert(pos_is_ok());
+ assert(pos_is_ok());
}
+
+// Must be used to undo a "null move"
void Position::undo_null_move() {
- assert(!checkers());
+ assert(!checkers());
- st = st->previous;
- sideToMove = ~sideToMove;
+ st = st->previous;
+ sideToMove = ~sideToMove;
}
-/// Position::key_after() computes the new hash key after the given move. Needed
-/// for speculative prefetch. It doesn't recognize special moves like castling,
-/// en-passant and promotions.
-
+// Computes the new hash key after the given move. Needed
+// for speculative prefetch. It doesn't recognize special moves like castling,
+// en passant and promotions.
Key Position::key_after(Move m) const {
- Square from = from_sq(m);
- Square to = to_sq(m);
- Piece pc = piece_on(from);
- Piece captured = piece_on(to);
- Key k = st->key ^ Zobrist::side;
+ Square from = from_sq(m);
+ Square to = to_sq(m);
+ Piece pc = piece_on(from);
+ Piece captured = piece_on(to);
+ Key k = st->key ^ Zobrist::side;
- if (captured)
- k ^= Zobrist::psq[captured][to];
+ if (captured)
+ k ^= Zobrist::psq[captured][to];
- return k ^ Zobrist::psq[pc][to] ^ Zobrist::psq[pc][from];
-}
+ k ^= Zobrist::psq[pc][to] ^ Zobrist::psq[pc][from];
+ return (captured || type_of(pc) == PAWN) ? k : adjust_key50<true>(k);
+}
-/// Position::see() is a static exchange evaluator: It tries to estimate the
-/// material gain or loss resulting from a move.
-Value Position::see_sign(Move m) const {
+// Tests if the SEE (Static Exchange Evaluation)
+// value of move is greater or equal to the given threshold. We'll use an
+// algorithm similar to alpha-beta pruning with a null window.
+bool Position::see_ge(Move m, Value threshold) const {
+
+ assert(is_ok(m));
+
+ // Only deal with normal moves, assume others pass a simple SEE
+ if (type_of(m) != NORMAL)
+ return VALUE_ZERO >= threshold;
+
+ Square from = from_sq(m), to = to_sq(m);
+
+ int swap = PieceValue[piece_on(to)] - threshold;
+ if (swap < 0)
+ return false;
+
+ swap = PieceValue[piece_on(from)] - swap;
+ if (swap <= 0)
+ return true;
+
+ assert(color_of(piece_on(from)) == sideToMove);
+ Bitboard occupied = pieces() ^ from ^ to; // xoring to is important for pinned piece logic
+ Color stm = sideToMove;
+ Bitboard attackers = attackers_to(to, occupied);
+ Bitboard stmAttackers, bb;
+ int res = 1;
+
+ while (true)
+ {
+ stm = ~stm;
+ attackers &= occupied;
+
+ // If stm has no more attackers then give up: stm loses
+ if (!(stmAttackers = attackers & pieces(stm)))
+ break;
+
+ // Don't allow pinned pieces to attack as long as there are
+ // pinners on their original square.
+ if (pinners(~stm) & occupied)
+ {
+ stmAttackers &= ~blockers_for_king(stm);
+
+ if (!stmAttackers)
+ break;
+ }
+
+ res ^= 1;
+
+ // Locate and remove the next least valuable attacker, and add to
+ // the bitboard 'attackers' any X-ray attackers behind it.
+ if ((bb = stmAttackers & pieces(PAWN)))
+ {
+ if ((swap = PawnValue - swap) < res)
+ break;
+ occupied ^= least_significant_square_bb(bb);
+
+ attackers |= attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN);
+ }
+
+ else if ((bb = stmAttackers & pieces(KNIGHT)))
+ {
+ if ((swap = KnightValue - swap) < res)
+ break;
+ occupied ^= least_significant_square_bb(bb);
+ }
+
+ else if ((bb = stmAttackers & pieces(BISHOP)))
+ {
+ if ((swap = BishopValue - swap) < res)
+ break;
+ occupied ^= least_significant_square_bb(bb);
+
+ attackers |= attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN);
+ }
+
+ else if ((bb = stmAttackers & pieces(ROOK)))
+ {
+ if ((swap = RookValue - swap) < res)
+ break;
+ occupied ^= least_significant_square_bb(bb);
+
+ attackers |= attacks_bb<ROOK>(to, occupied) & pieces(ROOK, QUEEN);
+ }
+
+ else if ((bb = stmAttackers & pieces(QUEEN)))
+ {
+ if ((swap = QueenValue - swap) < res)
+ break;
+ occupied ^= least_significant_square_bb(bb);
+
+ attackers |= (attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN))
+ | (attacks_bb<ROOK>(to, occupied) & pieces(ROOK, QUEEN));
+ }
+
+ else // KING
+ // If we "capture" with the king but the opponent still has attackers,
+ // reverse the result.
+ return (attackers & ~pieces(stm)) ? res ^ 1 : res;
+ }
+
+ return bool(res);
+}
- assert(is_ok(m));
+// Tests whether the position is drawn by 50-move rule
+// or by repetition. It does not detect stalemates.
+bool Position::is_draw(int ply) const {
- // Early return if SEE cannot be negative because captured piece value
- // is not less then capturing one. Note that king moves always return
- // here because king midgame value is set to 0.
- if (PieceValue[MG][moved_piece(m)] <= PieceValue[MG][piece_on(to_sq(m))])
- return VALUE_KNOWN_WIN;
+ if (st->rule50 > 99 && (!checkers() || MoveList<LEGAL>(*this).size()))
+ return true;
- return see(m);
+ // Return a draw score if a position repeats once earlier but strictly
+ // after the root, or repeats twice before or at the root.
+ return st->repetition && st->repetition < ply;
}
-Value Position::see(Move m) const {
-
- Square from, to;
- Bitboard occupied, attackers, stmAttackers;
- Value swapList[32];
- int slIndex = 1;
- PieceType captured;
- Color stm;
-
- assert(is_ok(m));
-
- from = from_sq(m);
- to = to_sq(m);
- swapList[0] = PieceValue[MG][piece_on(to)];
- stm = color_of(piece_on(from));
- occupied = pieces() ^ from;
-
- // Castling moves are implemented as king capturing the rook so cannot
- // be handled correctly. Simply return VALUE_ZERO that is always correct
- // unless in the rare case the rook ends up under attack.
- if (type_of(m) == CASTLING)
- return VALUE_ZERO;
-
- if (type_of(m) == ENPASSANT)
- {
- occupied ^= to - pawn_push(stm); // Remove the captured pawn
- swapList[0] = PieceValue[MG][PAWN];
- }
-
- // Find all attackers to the destination square, with the moving piece
- // removed, but possibly an X-ray attacker added behind it.
- attackers = attackers_to(to, occupied) & occupied;
-
- // If the opponent has no attackers we are finished
- stm = ~stm;
- stmAttackers = attackers & pieces(stm);
- if (!stmAttackers)
- return swapList[0];
-
- // Don't allow pinned pieces to attack as long all pinners (this includes also
- // potential ones) are on their original square. When a pinner moves to the
- // exchange-square or get captured on it, we fall back to standard SEE behaviour.
- else if ( (stmAttackers & st->blockersForKing[stm])
- && ((st->pinnersForKing[stm] & (occupied ^ (occupied & to))) == st->pinnersForKing[stm]))
- {
- // Pinned pieces can't attack so remove them from attackers
- stmAttackers ^= (stmAttackers & st->blockersForKing[stm]);
- if (!stmAttackers)
- return swapList[0];
- }
-
- // The destination square is defended, which makes things rather more
- // difficult to compute. We proceed by building up a "swap list" containing
- // the material gain or loss at each stop in a sequence of captures to the
- // destination square, where the sides alternately capture, and always
- // capture with the least valuable piece. After each capture, we look for
- // new X-ray attacks from behind the capturing piece.
- captured = type_of(piece_on(from));
-
- do {
- assert(slIndex < 32);
-
- // Add the new entry to the swap list
- swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured];
-
- // Locate and remove the next least valuable attacker
- captured = min_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
- stm = ~stm;
- stmAttackers = attackers & pieces(stm);
- if ( stmAttackers
- && (stmAttackers & st->blockersForKing[stm])
- && ((st->pinnersForKing[stm] & (occupied ^ (occupied & to))) == st->pinnersForKing[stm]))
- stmAttackers ^= (stmAttackers & st->blockersForKing[stm]);
-
- ++slIndex;
-
- } while (stmAttackers && (captured != KING || (--slIndex, false))); // Stop before a king capture
-
- // Having built the swap list, we negamax through it to find the best
- // achievable score from the point of view of the side to move.
- while (--slIndex)
- swapList[slIndex - 1] = std::min(-swapList[slIndex], swapList[slIndex - 1]);
-
- return swapList[0];
+
+// Tests whether there has been at least one repetition
+// of positions since the last capture or pawn move.
+bool Position::has_repeated() const {
+
+ StateInfo* stc = st;
+ int end = std::min(st->rule50, st->pliesFromNull);
+ while (end-- >= 4)
+ {
+ if (stc->repetition)
+ return true;
+
+ stc = stc->previous;
+ }
+ return false;
}
-/// Position::is_draw() tests whether the position is drawn by 50-move rule
-/// or by repetition. It does not detect stalemates.
+// Tests if the position has a move which draws by repetition,
+// or an earlier position has a move that directly reaches the current position.
+bool Position::has_game_cycle(int ply) const {
-bool Position::is_draw() const {
+ int j;
- if (st->rule50 > 99 && (!checkers() || MoveList<LEGAL>(*this).size()))
- return true;
+ int end = std::min(st->rule50, st->pliesFromNull);
- StateInfo* stp = st;
- for (int i = 2, e = std::min(st->rule50, st->pliesFromNull); i <= e; i += 2)
- {
- stp = stp->previous->previous;
+ if (end < 3)
+ return false;
- if (stp->key == st->key)
- return true; // Draw at first repetition
- }
+ Key originalKey = st->key;
+ StateInfo* stp = st->previous;
- return false;
-}
+ for (int i = 3; i <= end; i += 2)
+ {
+ stp = stp->previous->previous;
+ Key moveKey = originalKey ^ stp->key;
+ if ((j = H1(moveKey), cuckoo[j] == moveKey) || (j = H2(moveKey), cuckoo[j] == moveKey))
+ {
+ Move move = cuckooMove[j];
+ Square s1 = from_sq(move);
+ Square s2 = to_sq(move);
-/// Position::flip() flips position with the white and black sides reversed. This
-/// is only useful for debugging e.g. for finding evaluation symmetry bugs.
+ if (!((between_bb(s1, s2) ^ s2) & pieces()))
+ {
+ if (ply > i)
+ return true;
+ // For nodes before or at the root, check that the move is a
+ // repetition rather than a move to the current position.
+ // In the cuckoo table, both moves Rc1c5 and Rc5c1 are stored in
+ // the same location, so we have to select which square to check.
+ if (color_of(piece_on(empty(s1) ? s2 : s1)) != side_to_move())
+ continue;
+
+ // For repetitions before or at the root, require one more
+ if (stp->repetition)
+ return true;
+ }
+ }
+ }
+ return false;
+}
+
+
+// Flips position with the white and black sides reversed. This
+// is only useful for debugging e.g. for finding evaluation symmetry bugs.
void Position::flip() {
- string f, token;
- std::stringstream ss(fen());
+ string f, token;
+ std::stringstream ss(fen());
- for (Rank r = RANK_8; r >= RANK_1; --r) // Piece placement
- {
- std::getline(ss, token, r > RANK_1 ? '/' : ' ');
- f.insert(0, token + (f.empty() ? " " : "/"));
- }
+ for (Rank r = RANK_8; r >= RANK_1; --r) // Piece placement
+ {
+ std::getline(ss, token, r > RANK_1 ? '/' : ' ');
+ f.insert(0, token + (f.empty() ? " " : "/"));
+ }
- ss >> token; // Active color
- f += (token == "w" ? "B " : "W "); // Will be lowercased later
+ ss >> token; // Active color
+ f += (token == "w" ? "B " : "W "); // Will be lowercased later
- ss >> token; // Castling availability
- f += token + " ";
+ ss >> token; // Castling availability
+ f += token + " ";
- std::transform(f.begin(), f.end(), f.begin(),
- [](char c) { return char(islower(c) ? toupper(c) : tolower(c)); });
+ std::transform(f.begin(), f.end(), f.begin(),
+ [](char c) { return char(islower(c) ? toupper(c) : tolower(c)); });
- ss >> token; // En passant square
- f += (token == "-" ? token : token.replace(1, 1, token[1] == '3' ? "6" : "3"));
+ ss >> token; // En passant square
+ f += (token == "-" ? token : token.replace(1, 1, token[1] == '3' ? "6" : "3"));
- std::getline(ss, token); // Half and full moves
- f += token;
+ std::getline(ss, token); // Half and full moves
+ f += token;
- set(f, is_chess960(), st, this_thread());
+ set(f, is_chess960(), st, this_thread());
- assert(pos_is_ok());
+ assert(pos_is_ok());
}
-/// Position::pos_is_ok() performs some consistency checks for the position object.
-/// This is meant to be helpful when debugging.
-
-bool Position::pos_is_ok(int* failedStep) const {
-
- const bool Fast = true; // Quick (default) or full check?
-
- enum { Default, King, Bitboards, State, Lists, Castling };
-
- for (int step = Default; step <= (Fast ? Default : Castling); step++)
- {
- if (failedStep)
- *failedStep = step;
-
- if (step == Default)
- if ( (sideToMove != WHITE && sideToMove != BLACK)
- || piece_on(square<KING>(WHITE)) != W_KING
- || piece_on(square<KING>(BLACK)) != B_KING
- || ( ep_square() != SQ_NONE
- && relative_rank(sideToMove, ep_square()) != RANK_6))
- return false;
-
- if (step == King)
- if ( std::count(board, board + SQUARE_NB, W_KING) != 1
- || std::count(board, board + SQUARE_NB, B_KING) != 1
- || attackers_to(square<KING>(~sideToMove)) & pieces(sideToMove))
- return false;
-
- if (step == Bitboards)
- {
- if ( (pieces(WHITE) & pieces(BLACK))
- ||(pieces(WHITE) | pieces(BLACK)) != pieces())
- return false;
-
- for (PieceType p1 = PAWN; p1 <= KING; ++p1)
- for (PieceType p2 = PAWN; p2 <= KING; ++p2)
- if (p1 != p2 && (pieces(p1) & pieces(p2)))
- return false;
- }
-
- if (step == State)
- {
- StateInfo si = *st;
- set_state(&si);
- if (std::memcmp(&si, st, sizeof(StateInfo)))
- return false;
- }
-
- if (step == Lists)
- for (Piece pc : Pieces)
- {
- if (pieceCount[pc] != popcount(pieces(color_of(pc), type_of(pc))))
- return false;
-
- for (int i = 0; i < pieceCount[pc]; ++i)
- if (board[pieceList[pc][i]] != pc || index[pieceList[pc][i]] != i)
- return false;
- }
-
- if (step == Castling)
- for (Color c = WHITE; c <= BLACK; ++c)
- for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1))
- {
- if (!can_castle(c | s))
- continue;
-
- if ( piece_on(castlingRookSquare[c | s]) != make_piece(c, ROOK)
- || castlingRightsMask[castlingRookSquare[c | s]] != (c | s)
- ||(castlingRightsMask[square<KING>(c)] & (c | s)) != (c | s))
- return false;
- }
- }
-
- return true;
+// Performs some consistency checks for the position object
+// and raise an assert if something wrong is detected.
+// This is meant to be helpful when debugging.
+bool Position::pos_is_ok() const {
+
+ constexpr bool Fast = true; // Quick (default) or full check?
+
+ if ((sideToMove != WHITE && sideToMove != BLACK) || piece_on(square<KING>(WHITE)) != W_KING
+ || piece_on(square<KING>(BLACK)) != B_KING
+ || (ep_square() != SQ_NONE && relative_rank(sideToMove, ep_square()) != RANK_6))
+ assert(0 && "pos_is_ok: Default");
+
+ if (Fast)
+ return true;
+
+ if (pieceCount[W_KING] != 1 || pieceCount[B_KING] != 1
+ || attackers_to(square<KING>(~sideToMove)) & pieces(sideToMove))
+ assert(0 && "pos_is_ok: Kings");
+
+ if ((pieces(PAWN) & (Rank1BB | Rank8BB)) || pieceCount[W_PAWN] > 8 || pieceCount[B_PAWN] > 8)
+ assert(0 && "pos_is_ok: Pawns");
+
+ if ((pieces(WHITE) & pieces(BLACK)) || (pieces(WHITE) | pieces(BLACK)) != pieces()
+ || popcount(pieces(WHITE)) > 16 || popcount(pieces(BLACK)) > 16)
+ assert(0 && "pos_is_ok: Bitboards");
+
+ for (PieceType p1 = PAWN; p1 <= KING; ++p1)
+ for (PieceType p2 = PAWN; p2 <= KING; ++p2)
+ if (p1 != p2 && (pieces(p1) & pieces(p2)))
+ assert(0 && "pos_is_ok: Bitboards");
+
+
+ for (Piece pc : Pieces)
+ if (pieceCount[pc] != popcount(pieces(color_of(pc), type_of(pc)))
+ || pieceCount[pc] != std::count(board, board + SQUARE_NB, pc))
+ assert(0 && "pos_is_ok: Pieces");
+
+ for (Color c : {WHITE, BLACK})
+ for (CastlingRights cr : {c & KING_SIDE, c & QUEEN_SIDE})
+ {
+ if (!can_castle(cr))
+ continue;
+
+ if (piece_on(castlingRookSquare[cr]) != make_piece(c, ROOK)
+ || castlingRightsMask[castlingRookSquare[cr]] != cr
+ || (castlingRightsMask[square<KING>(c)] & cr) != cr)
+ assert(0 && "pos_is_ok: Castling");
+ }
+
+ return true;
}
+
+} // namespace Stockfish
projects / stockfish / blobdiff