/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <algorithm>
#include <cassert>
-#include <cstring>
-#include <fstream>
-#include <map>
-#include <iostream>
+#include <cstddef> // For offsetof()
+#include <cstring> // For std::memset, std::memcmp
+#include <iomanip>
#include <sstream>
-#include "bitcount.h"
+#include "bitboard.h"
+#include "misc.h"
#include "movegen.h"
#include "position.h"
-#include "psqtab.h"
-#include "rkiss.h"
#include "thread.h"
#include "tt.h"
-#include "ucioption.h"
+#include "uci.h"
+#include "syzygy/tbprobe.h"
using std::string;
-using std::cout;
-using std::endl;
-
-Key Position::zobrist[2][8][64];
-Key Position::zobEp[64];
-Key Position::zobCastle[16];
-Key Position::zobSideToMove;
-Key Position::zobExclusion;
-
-Score Position::PieceSquareTable[16][64];
-
-// Material values arrays, indexed by Piece
-const Value Position::PieceValueMidgame[17] = {
- VALUE_ZERO,
- PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
- RookValueMidgame, QueenValueMidgame, VALUE_ZERO,
- VALUE_ZERO, VALUE_ZERO,
- PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
- RookValueMidgame, QueenValueMidgame
-};
-
-const Value Position::PieceValueEndgame[17] = {
- VALUE_ZERO,
- PawnValueEndgame, KnightValueEndgame, BishopValueEndgame,
- RookValueEndgame, QueenValueEndgame, VALUE_ZERO,
- VALUE_ZERO, VALUE_ZERO,
- PawnValueEndgame, KnightValueEndgame, BishopValueEndgame,
- RookValueEndgame, QueenValueEndgame
-};
-
-// Material values array used by SEE, indexed by PieceType
-const Value Position::seeValues[] = {
- VALUE_ZERO,
- PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
- RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10
-};
+namespace Zobrist {
+
+ Key psq[PIECE_NB][SQUARE_NB];
+ Key enpassant[FILE_NB];
+ Key castling[CASTLING_RIGHT_NB];
+ Key side, noPawns;
+}
namespace {
- // Bonus for having the side to move (modified by Joona Kiiski)
- const Score TempoValue = make_score(48, 22);
+const string PieceToChar(" PNBRQK pnbrqk");
- struct PieceLetters : public std::map<char, Piece> {
+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
- PieceLetters() {
- operator[]('K') = WK; operator[]('k') = BK;
- operator[]('Q') = WQ; operator[]('q') = BQ;
- operator[]('R') = WR; operator[]('r') = BR;
- operator[]('B') = WB; operator[]('b') = BB;
- operator[]('N') = WN; operator[]('n') = BN;
- operator[]('P') = WP; operator[]('p') = BP;
- operator[](' ') = PIECE_NONE;
- operator[]('.') = PIECE_NONE_DARK_SQ;
- }
+/// operator<<(Position) returns an ASCII representation of the position
- char from_piece(Piece p) const {
+std::ostream& operator<<(std::ostream& os, const Position& pos) {
- std::map<char, Piece>::const_iterator it;
- for (it = begin(); it != end(); ++it)
- if (it->second == p)
- return it->first;
+ os << "\n +---+---+---+---+---+---+---+---+\n";
- assert(false);
- return 0;
- }
- };
+ 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))];
- PieceLetters pieceLetters;
-}
+ os << " |\n +---+---+---+---+---+---+---+---+\n";
+ }
+ os << "\nFen: " << pos.fen() << "\nKey: " << std::hex << std::uppercase
+ << std::setfill('0') << std::setw(16) << pos.key()
+ << std::setfill(' ') << std::dec << "\nCheckers: ";
-/// CheckInfo c'tor
+ for (Bitboard b = pos.checkers(); b; )
+ os << UCI::square(pop_lsb(&b)) << " ";
-CheckInfo::CheckInfo(const Position& pos) {
+ if ( int(Tablebases::MaxCardinality) >= popcount(pos.pieces())
+ && !pos.can_castle(ANY_CASTLING))
+ {
+ StateInfo st;
+ 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 << ")";
+ }
- Color us = pos.side_to_move();
- Color them = opposite_color(us);
+ return os;
+}
- ksq = pos.king_square(them);
- dcCandidates = pos.discovered_check_candidates(us);
- checkSq[PAWN] = pos.attacks_from<PAWN>(ksq, them);
- checkSq[KNIGHT] = pos.attacks_from<KNIGHT>(ksq);
- checkSq[BISHOP] = pos.attacks_from<BISHOP>(ksq);
- checkSq[ROOK] = pos.attacks_from<ROOK>(ksq);
- checkSq[QUEEN] = checkSq[BISHOP] | checkSq[ROOK];
- checkSq[KING] = EmptyBoardBB;
-}
+// Marcel van Kervinck's cuckoo algorithm for fast detection of "upcoming repetition"
+// situations. Description of the algorithm in the following paper:
+// https://marcelk.net/2013-04-06/paper/upcoming-rep-v2.pdf
+// 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; }
-/// Position c'tors. Here we always create a copy of the original position
-/// or the FEN string, we want the new born Position object do not depend
-/// on any external data so we detach state pointer from the source one.
+// Cuckoo tables with Zobrist hashes of valid reversible moves, and the moves themselves
+Key cuckoo[8192];
+Move cuckooMove[8192];
-Position::Position(const Position& pos, int th) {
- memcpy(this, &pos, sizeof(Position));
- detach(); // Always detach() in copy c'tor to avoid surprises
- threadID = th;
- nodes = 0;
-}
+/// Position::init() initializes at startup the various arrays used to compute
+/// hash keys.
-Position::Position(const string& fen, bool isChess960, int th) {
+void Position::init() {
- from_fen(fen, isChess960);
- threadID = th;
-}
+ PRNG rng(1070372);
+ for (Piece pc : Pieces)
+ for (Square s = SQ_A1; s <= SQ_H8; ++s)
+ Zobrist::psq[pc][s] = rng.rand<Key>();
-/// Position::detach() copies the content of the current state and castling
-/// masks inside the position itself. This is needed when the st pointee could
-/// become stale, as example because the caller is about to going out of scope.
+ for (File f = FILE_A; f <= FILE_H; ++f)
+ Zobrist::enpassant[f] = rng.rand<Key>();
-void Position::detach() {
+ 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>();
+ }
+ }
- startState = *st;
- st = &startState;
- st->previous = NULL; // as a safe guard
+ 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));
+ 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 (PseudoAttacks[type_of(pc)][s1] & 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::from_fen() 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::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.
-void Position::from_fen(const string& fen, bool isChess960) {
+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. The separator between fields is a space. The fields are:
+ A FEN string contains six fields separated by a space. The fields are:
- 1) Piece placement (from white's perspective). Each rank is described, starting with rank 8 and ending
- with rank 1; within each rank, the contents of each square are described from file A through file H.
- Following the Standard Algebraic Notation (SAN), each piece is identified by a single letter taken
- from the standard English names. White pieces are designated using upper-case letters ("PNBRQK")
- while Black take lowercase ("pnbrqk"). Blank squares are noted using digits 1 through 8 (the number
- of blank squares), and "/" separate ranks.
+ 1) Piece placement (from white's perspective). Each rank is described, starting
+ with rank 8 and ending with rank 1. Within each rank, the contents of each
+ square are described from file A through file H. Following the Standard
+ Algebraic Notation (SAN), each piece is identified by a single letter taken
+ from the standard English names. White pieces are designated using upper-case
+ letters ("PNBRQK") whilst Black uses lowercase ("pnbrqk"). Blank squares are
+ noted using digits 1 through 8 (the number of blank squares), and "/"
+ separates ranks.
2) Active color. "w" means white moves next, "b" means black.
- 3) Castling availability. If neither side can castle, this is "-". Otherwise, this has one or more
- letters: "K" (White can castle kingside), "Q" (White can castle queenside), "k" (Black can castle
- kingside), and/or "q" (Black can castle queenside).
+ 3) Castling availability. If neither side can castle, this is "-". Otherwise,
+ this has one or more letters: "K" (White can castle kingside), "Q" (White
+ can castle queenside), "k" (Black can castle kingside), and/or "q" (Black
+ can castle queenside).
- 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.
+ 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 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 fifty-move rule.
+ 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
+ fifty-move rule.
- 6) Fullmove number: The number of the full move. It starts at 1, and is incremented after Black's move.
+ 6) Fullmove number. The number of the full move. It starts at 1, and is
+ incremented after Black's move.
*/
- char token;
- int hmc, fmn;
- std::istringstream ss(fen);
+ unsigned char col, row, token;
+ size_t idx;
Square sq = SQ_A8;
+ std::istringstream ss(fenStr);
- clear();
+ 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;
- // 1. Piece placement field
- while (ss.get(token) && token != ' ')
+ ss >> std::noskipws;
+
+ // 1. Piece placement
+ while ((ss >> token) && !isspace(token))
{
- if (pieceLetters.find(token) != pieceLetters.end())
+ 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(pieceLetters[token], sq);
- sq++;
+ put_piece(Piece(idx), sq);
+ ++sq;
}
- else if (isdigit(token))
- sq += Square(token - '0'); // Skip the given number of files
- else if (token == '/')
- sq -= SQ_A3; // Jump back of 2 rows
- else
- goto incorrect_fen;
}
// 2. Active color
- if (!ss.get(token) || (token != 'w' && token != 'b'))
- goto incorrect_fen;
-
+ ss >> token;
sideToMove = (token == 'w' ? WHITE : BLACK);
-
- if (!ss.get(token) || token != ' ')
- goto incorrect_fen;
-
- // 3. Castling availability
- while (ss.get(token) && token != ' ')
- if (!set_castling_rights(token))
- goto incorrect_fen;
-
- // 4. En passant square
- char col, row;
- if ( (ss.get(col) && (col >= 'a' && col <= 'h'))
- && (ss.get(row) && (row == '3' || row == '6')))
+ 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))
{
- st->epSquare = make_square(file_from_char(col), rank_from_char(row));
+ Square rsq;
+ Color c = islower(token) ? BLACK : WHITE;
+ Piece rook = make_piece(c, ROOK);
- // Ignore if no capture is possible
- Color them = opposite_color(sideToMove);
- if (!(attacks_from<PAWN>(st->epSquare, them) & pieces(PAWN, sideToMove)))
- st->epSquare = SQ_NONE;
- }
+ token = char(toupper(token));
- // 5. Halfmove clock
- if (ss >> hmc)
- st->rule50 = hmc;
+ if (token == 'K')
+ for (rsq = relative_square(c, SQ_H1); piece_on(rsq) != rook; --rsq) {}
- // 6. Fullmove number
- if (ss >> fmn)
- startPosPlyCounter = (fmn - 1) * 2 + int(sideToMove == BLACK);
+ else if (token == 'Q')
+ for (rsq = relative_square(c, SQ_A1); piece_on(rsq) != rook; ++rsq) {}
- // Various initialisations
- castleRightsMask[make_square(initialKFile, RANK_1)] ^= WHITE_OO | WHITE_OOO;
- castleRightsMask[make_square(initialKFile, RANK_8)] ^= BLACK_OO | BLACK_OOO;
- castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO;
- castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO;
- castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO;
- castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO;
+ else if (token >= 'A' && token <= 'H')
+ rsq = make_square(File(token - 'A'), relative_rank(c, RANK_1));
- chess960 = isChess960;
- find_checkers();
-
- st->key = compute_key();
- st->pawnKey = compute_pawn_key();
- st->materialKey = compute_material_key();
- st->value = compute_value();
- st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
- st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
- return;
-
-incorrect_fen:
- cout << "Error in FEN string: " << fen << endl;
-}
+ else
+ continue;
+ set_castling_right(c, rsq);
+ }
-/// Position::set_castling_rights() sets castling parameters castling avaiability.
-/// This function is 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 traditional castling tag will be replaced
-/// by the file letter of the involved rook as for the Shredder-FEN.
+ // 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'));
-bool Position::set_castling_rights(char token) {
+ if ( !(attackers_to(st->epSquare) & pieces(sideToMove, PAWN))
+ || !(pieces(~sideToMove, PAWN) & (st->epSquare + pawn_push(~sideToMove))))
+ st->epSquare = SQ_NONE;
+ }
+ else
+ st->epSquare = SQ_NONE;
- Color c = token >= 'a' ? BLACK : WHITE;
- Square sqA = (c == WHITE ? SQ_A1 : SQ_A8);
- Square sqH = (c == WHITE ? SQ_H1 : SQ_H8);
- Piece rook = (c == WHITE ? WR : BR);
+ // 5-6. Halfmove clock and fullmove number
+ ss >> std::skipws >> st->rule50 >> gamePly;
- initialKFile = square_file(king_square(c));
- token = char(toupper(token));
+ // 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);
- if (token == 'K')
- {
- for (Square sq = sqH; sq >= sqA; sq--)
- if (piece_on(sq) == rook)
- {
- do_allow_oo(c);
- initialKRFile = square_file(sq);
- break;
- }
- }
- else if (token == 'Q')
- {
- for (Square sq = sqA; sq <= sqH; sq++)
- if (piece_on(sq) == rook)
- {
- do_allow_ooo(c);
- initialQRFile = square_file(sq);
- break;
- }
- }
- else if (token >= 'A' && token <= 'H')
- {
- File rookFile = File(token - 'A') + FILE_A;
- if (rookFile < initialKFile)
- {
- do_allow_ooo(c);
- initialQRFile = rookFile;
- }
- else
- {
- do_allow_oo(c);
- initialKRFile = rookFile;
- }
- }
- else
- return token == '-';
+ chess960 = isChess960;
+ thisThread = th;
+ set_state(st);
- return true;
+ assert(pos_is_ok());
+
+ return *this;
}
-/// Position::to_fen() returns a FEN representation of the position. In case
-/// of Chess960 the Shredder-FEN notation is used. Mainly a debugging function.
+/// Position::set_castling_right() is a helper function used to set castling
+/// rights given the corresponding color and the rook starting square.
-const string Position::to_fen() const {
+void Position::set_castling_right(Color c, Square rfrom) {
- string fen;
- Square sq;
- char emptyCnt = '0';
+ Square kfrom = square<KING>(c);
+ CastlingRights cr = c & (kfrom < rfrom ? KING_SIDE: QUEEN_SIDE);
- for (Rank rank = RANK_8; rank >= RANK_1; rank--, fen += '/')
- {
- for (File file = FILE_A; file <= FILE_H; file++)
- {
- sq = make_square(file, rank);
+ st->castlingRights |= cr;
+ castlingRightsMask[kfrom] |= cr;
+ castlingRightsMask[rfrom] |= cr;
+ castlingRookSquare[cr] = rfrom;
- if (square_is_occupied(sq))
- {
- if (emptyCnt != '0')
- {
- fen += emptyCnt;
- emptyCnt = '0';
- }
- fen += pieceLetters.from_piece(piece_on(sq));
- } else
- emptyCnt++;
- }
+ Square kto = relative_square(c, cr & KING_SIDE ? SQ_G1 : SQ_C1);
+ Square rto = relative_square(c, cr & KING_SIDE ? SQ_F1 : SQ_D1);
- if (emptyCnt != '0')
- {
- fen += emptyCnt;
- emptyCnt = '0';
- }
- }
+ castlingPath[cr] = (between_bb(rfrom, rto) | between_bb(kfrom, kto) | rto | kto)
+ & ~(square_bb(kfrom) | rfrom);
+}
- fen += (sideToMove == WHITE ? " w " : " b ");
- if (st->castleRights != CASTLES_NONE)
- {
- if (can_castle_kingside(WHITE))
- fen += chess960 ? char(toupper(file_to_char(initialKRFile))) : 'K';
+/// Position::set_check_info() sets king attacks to detect if a move gives check
- if (can_castle_queenside(WHITE))
- fen += chess960 ? char(toupper(file_to_char(initialQRFile))) : 'Q';
+void Position::set_check_info(StateInfo* si) const {
- if (can_castle_kingside(BLACK))
- fen += chess960 ? file_to_char(initialKRFile) : 'k';
+ si->blockersForKing[WHITE] = slider_blockers(pieces(BLACK), square<KING>(WHITE), si->pinners[BLACK]);
+ si->blockersForKing[BLACK] = slider_blockers(pieces(WHITE), square<KING>(BLACK), si->pinners[WHITE]);
- if (can_castle_queenside(BLACK))
- fen += chess960 ? file_to_char(initialQRFile) : 'q';
- } else
- fen += '-';
+ Square ksq = square<KING>(~sideToMove);
- fen += (ep_square() == SQ_NONE ? " -" : " " + square_to_string(ep_square()));
- return fen;
+ 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;
}
-/// Position::print() prints an ASCII representation of the position to
-/// the standard output. If a move is given then also the san is printed.
+/// 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.
-void Position::print(Move move) const {
+void Position::set_state(StateInfo* si) const {
- const char* dottedLine = "\n+---+---+---+---+---+---+---+---+\n";
+ si->key = si->materialKey = 0;
+ si->pawnKey = Zobrist::noPawns;
+ si->nonPawnMaterial[WHITE] = si->nonPawnMaterial[BLACK] = VALUE_ZERO;
+ si->checkersBB = attackers_to(square<KING>(sideToMove)) & pieces(~sideToMove);
- if (move)
- {
- Position p(*this, thread());
- string dd = (color_of_piece_on(move_from(move)) == BLACK ? ".." : "");
- cout << "\nMove is: " << dd << move_to_san(p, move);
- }
+ set_check_info(si);
- for (Rank rank = RANK_8; rank >= RANK_1; rank--)
+ for (Bitboard b = pieces(); b; )
{
- cout << dottedLine << '|';
- for (File file = FILE_A; file <= FILE_H; file++)
- {
- Square sq = make_square(file, rank);
- Piece piece = piece_on(sq);
+ Square s = pop_lsb(&b);
+ Piece pc = piece_on(s);
+ si->key ^= Zobrist::psq[pc][s];
- if (piece == PIECE_NONE && square_color(sq) == DARK)
- piece = PIECE_NONE_DARK_SQ;
+ if (type_of(pc) == PAWN)
+ si->pawnKey ^= Zobrist::psq[pc][s];
- char c = (color_of_piece_on(sq) == BLACK ? '=' : ' ');
- cout << c << pieceLetters.from_piece(piece) << c << '|';
- }
+ else if (type_of(pc) != KING)
+ si->nonPawnMaterial[color_of(pc)] += PieceValue[MG][pc];
}
- cout << dottedLine << "Fen is: " << to_fen() << "\nKey is: " << st->key << endl;
-}
+ if (si->epSquare != SQ_NONE)
+ si->key ^= Zobrist::enpassant[file_of(si->epSquare)];
-/// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
-/// king) pieces for the given color and for the given pinner type. Or, when
-/// template parameter FindPinned is false, the pieces of the given color
-/// candidate for a discovery check against the enemy king.
-/// Bitboard checkersBB must be already updated when looking for pinners.
+ if (sideToMove == BLACK)
+ si->key ^= Zobrist::side;
-template<bool FindPinned>
-Bitboard Position::hidden_checkers(Color c) const {
+ si->key ^= Zobrist::castling[si->castlingRights];
- Bitboard result = EmptyBoardBB;
- Bitboard pinners = pieces_of_color(FindPinned ? opposite_color(c) : c);
-
- // Pinned pieces protect our king, dicovery checks attack
- // the enemy king.
- Square ksq = king_square(FindPinned ? c : opposite_color(c));
-
- // Pinners are sliders, not checkers, that give check when candidate pinned is removed
- pinners &= (pieces(ROOK, QUEEN) & RookPseudoAttacks[ksq]) | (pieces(BISHOP, QUEEN) & BishopPseudoAttacks[ksq]);
-
- if (FindPinned && pinners)
- pinners &= ~st->checkersBB;
-
- while (pinners)
- {
- Square s = pop_1st_bit(&pinners);
- Bitboard b = squares_between(s, ksq) & occupied_squares();
-
- assert(b);
-
- if ( !(b & (b - 1)) // Only one bit set?
- && (b & pieces_of_color(c))) // Is an our piece?
- result |= b;
- }
- return result;
+ for (Piece pc : Pieces)
+ for (int cnt = 0; cnt < pieceCount[pc]; ++cnt)
+ si->materialKey ^= Zobrist::psq[pc][cnt];
}
-/// Position:pinned_pieces() returns a bitboard of all pinned (against the
-/// king) pieces for the given color. Note that checkersBB bitboard must
-/// be already updated.
+/// Position::set() is an overload to initialize the position object with
+/// the given endgame code string like "KBPKN". It is mainly a helper to
+/// get the material key out of an endgame code.
-Bitboard Position::pinned_pieces(Color c) const {
+Position& Position::set(const string& code, Color c, StateInfo* si) {
- return hidden_checkers<true>(c);
-}
+ assert(code.length() > 0 && code.length() < 8);
+ assert(code[0] == 'K');
+ string sides[] = { code.substr(code.find('K', 1)), // Weak
+ code.substr(0, code.find('K', 1)) }; // Strong
-/// Position:discovered_check_candidates() returns a bitboard containing all
-/// pieces for the given side which are candidates for giving a discovered
-/// check. Contrary to pinned_pieces() here there is no need of checkersBB
-/// to be already updated.
+ std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
-Bitboard Position::discovered_check_candidates(Color c) const {
+ 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";
- return hidden_checkers<false>(c);
+ return set(fenStr, false, si, nullptr);
}
-/// Position::attackers_to() computes a bitboard containing all pieces which
-/// attacks a given square.
-
-Bitboard Position::attackers_to(Square s) const {
- return (attacks_from<PAWN>(s, BLACK) & pieces(PAWN, WHITE))
- | (attacks_from<PAWN>(s, WHITE) & pieces(PAWN, BLACK))
- | (attacks_from<KNIGHT>(s) & pieces(KNIGHT))
- | (attacks_from<ROOK>(s) & pieces(ROOK, QUEEN))
- | (attacks_from<BISHOP>(s) & pieces(BISHOP, QUEEN))
- | (attacks_from<KING>(s) & pieces(KING));
-}
-
-/// Position::attacks_from() computes a bitboard of all attacks
-/// of a given piece put in a given square.
+/// 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.
-Bitboard Position::attacks_from(Piece p, Square s) const {
+const string Position::fen() const {
- assert(square_is_ok(s));
+ int emptyCnt;
+ std::ostringstream ss;
- switch (p)
+ for (Rank r = RANK_8; r >= RANK_1; --r)
{
- case WB: case BB: return attacks_from<BISHOP>(s);
- case WR: case BR: return attacks_from<ROOK>(s);
- case WQ: case BQ: return attacks_from<QUEEN>(s);
- default: return StepAttacksBB[p][s];
- }
-}
+ for (File f = FILE_A; f <= FILE_H; ++f)
+ {
+ for (emptyCnt = 0; f <= FILE_H && empty(make_square(f, r)); ++f)
+ ++emptyCnt;
-Bitboard Position::attacks_from(Piece p, Square s, Bitboard occ) {
+ if (emptyCnt)
+ ss << emptyCnt;
- assert(square_is_ok(s));
+ if (f <= FILE_H)
+ ss << PieceToChar[piece_on(make_square(f, r))];
+ }
- switch (p)
- {
- case WB: case BB: return bishop_attacks_bb(s, occ);
- case WR: case BR: return rook_attacks_bb(s, occ);
- case WQ: case BQ: return bishop_attacks_bb(s, occ) | rook_attacks_bb(s, occ);
- default: return StepAttacksBB[p][s];
+ if (r > RANK_1)
+ ss << '/';
}
-}
-
-/// Position::move_attacks_square() tests whether a move from the current
-/// position attacks a given square.
+ ss << (sideToMove == WHITE ? " w " : " b ");
-bool Position::move_attacks_square(Move m, Square s) const {
+ if (can_castle(WHITE_OO))
+ ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE_OO ))) : 'K');
- assert(move_is_ok(m));
- assert(square_is_ok(s));
+ if (can_castle(WHITE_OOO))
+ ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE_OOO))) : 'Q');
- Bitboard occ, xray;
- Square f = move_from(m), t = move_to(m);
+ if (can_castle(BLACK_OO))
+ ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK_OO ))) : 'k');
- assert(square_is_occupied(f));
+ if (can_castle(BLACK_OOO))
+ ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK_OOO))) : 'q');
- if (bit_is_set(attacks_from(piece_on(f), t), s))
- return true;
+ if (!can_castle(ANY_CASTLING))
+ ss << '-';
- // Move the piece and scan for X-ray attacks behind it
- occ = occupied_squares();
- do_move_bb(&occ, make_move_bb(f, t));
- xray = ( (rook_attacks_bb(s, occ) & pieces(ROOK, QUEEN))
- |(bishop_attacks_bb(s, occ) & pieces(BISHOP, QUEEN)))
- & pieces_of_color(color_of_piece_on(f));
+ ss << (ep_square() == SQ_NONE ? " - " : " " + UCI::square(ep_square()) + " ")
+ << st->rule50 << " " << 1 + (gamePly - (sideToMove == BLACK)) / 2;
- // If we have attacks we need to verify that are caused by our move
- // and are not already existent ones.
- return xray && (xray ^ (xray & attacks_from<QUEEN>(s)));
+ return ss.str();
}
-/// Position::find_checkers() computes the checkersBB bitboard, which
-/// contains a nonzero bit for each checking piece (0, 1 or 2). It
-/// currently works by calling Position::attackers_to, which is probably
-/// inefficient. Consider rewriting this function to use the last move
-/// played, like in non-bitboard versions of Glaurung.
+/// 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.
-void Position::find_checkers() {
+Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const {
- Color us = side_to_move();
- st->checkersBB = attackers_to(king_square(us)) & pieces_of_color(opposite_color(us));
-}
-
-
-/// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
+ Bitboard blockers = 0;
+ pinners = 0;
-bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
+ // Snipers are sliders that attack 's' when a piece and other snipers are removed
+ Bitboard snipers = ( (PseudoAttacks[ ROOK][s] & pieces(QUEEN, ROOK))
+ | (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders;
+ Bitboard occupancy = pieces() ^ snipers;
- assert(is_ok());
- assert(move_is_ok(m));
- assert(pinned == pinned_pieces(side_to_move()));
-
- // 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 (move_is_ep(m))
+ while (snipers)
{
- Color us = side_to_move();
- Color them = opposite_color(us);
- Square from = move_from(m);
- Square to = move_to(m);
- Square capsq = make_square(square_file(to), square_rank(from));
- Square ksq = king_square(us);
- Bitboard b = occupied_squares();
-
- assert(to == ep_square());
- assert(piece_on(from) == make_piece(us, PAWN));
- assert(piece_on(capsq) == make_piece(them, PAWN));
- assert(piece_on(to) == PIECE_NONE);
+ Square sniperSq = pop_lsb(&snipers);
+ Bitboard b = between_bb(s, sniperSq) & occupancy;
- clear_bit(&b, from);
- clear_bit(&b, capsq);
- set_bit(&b, to);
-
- return !(rook_attacks_bb(ksq, b) & pieces(ROOK, QUEEN, them))
- && !(bishop_attacks_bb(ksq, b) & pieces(BISHOP, QUEEN, them));
+ if (b && !more_than_one(b))
+ {
+ blockers |= b;
+ if (b & pieces(color_of(piece_on(s))))
+ pinners |= sniperSq;
+ }
}
+ return blockers;
+}
- Color us = side_to_move();
- Square from = move_from(m);
- assert(color_of_piece_on(from) == us);
- assert(piece_on(king_square(us)) == make_piece(us, KING));
+/// Position::attackers_to() computes a bitboard of all pieces which attack a
+/// given square. Slider attacks use the occupied bitboard to indicate occupancy.
- // 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 move_is_castle(m) || !(attackers_to(move_to(m)) & pieces_of_color(opposite_color(us)));
+Bitboard Position::attackers_to(Square s, Bitboard occupied) const {
- // 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
- || !bit_is_set(pinned, from)
- || squares_aligned(from, move_to(m), king_square(us));
+ 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));
}
-/// Position::pl_move_is_evasion() tests whether a pseudo-legal move is a legal evasion
+/// Position::legal() tests whether a pseudo-legal move is legal
-bool Position::pl_move_is_evasion(Move m, Bitboard pinned) const
-{
- assert(in_check());
+bool Position::legal(Move m) const {
- Color us = side_to_move();
- Square from = move_from(m);
- Square to = move_to(m);
+ assert(is_ok(m));
- // King moves and en-passant captures are verified in pl_move_is_legal()
- if (type_of_piece_on(from) == KING || move_is_ep(m))
- return pl_move_is_legal(m, pinned);
+ Color us = sideToMove;
+ Square from = from_sq(m);
+ Square to = to_sq(m);
- Bitboard target = checkers();
- Square checksq = pop_1st_bit(&target);
+ assert(color_of(moved_piece(m)) == us);
+ assert(piece_on(square<KING>(us)) == make_piece(us, KING));
- if (target) // double check ?
- return false;
+ // 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 capsq = to - pawn_push(us);
+ Bitboard occupied = (pieces() ^ from ^ capsq) | to;
- // Our move must be a blocking evasion or a capture of the checking piece
- target = squares_between(checksq, king_square(us)) | checkers();
- return bit_is_set(target, to) && pl_move_is_legal(m, pinned);
-}
+ 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))
+ && !(attacks_bb<BISHOP>(ksq, occupied) & pieces(~us, QUEEN, BISHOP));
+ }
-/// Position::move_is_legal() takes a position and a (not necessarily pseudo-legal)
-/// move and tests whether the move is legal. This version is not very fast and
-/// should be used only in non time-critical paths.
+ // 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;
-bool Position::move_is_legal(const Move m) const {
+ for (Square s = to; s != from; s += step)
+ if (attackers_to(s) & pieces(~us))
+ return false;
- MoveStack mlist[MAX_MOVES];
- MoveStack *cur, *last = generate<MV_PSEUDO_LEGAL>(*this, mlist);
+ // In case of Chess960, 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.
+ return !chess960
+ || !(attacks_bb<ROOK>(to, pieces() ^ to_sq(m)) & pieces(~us, ROOK, QUEEN));
+ }
- for (cur = mlist; cur != last; cur++)
- if (cur->move == m)
- return pl_move_is_legal(m, pinned_pieces(sideToMove));
+ // 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(~us));
- return false;
+ // 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));
}
-/// Fast version of Position::move_is_legal() that takes a position a move and
-/// a bitboard of pinned pieces as input, and tests whether the move is legal.
+/// 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.
-bool Position::move_is_legal(const Move m, Bitboard pinned) const {
-
- assert(is_ok());
- assert(pinned == pinned_pieces(sideToMove));
+bool Position::pseudo_legal(const Move m) const {
Color us = sideToMove;
- Color them = opposite_color(sideToMove);
- Square from = move_from(m);
- Square to = move_to(m);
- Piece pc = piece_on(from);
+ 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 (move_is_special(m))
- return move_is_legal(m);
+ if (type_of(m) != NORMAL)
+ return MoveList<LEGAL>(*this).contains(m);
// Is not a promotion, so promotion piece must be empty
- if (move_promotion_piece(m) - 2 != PIECE_TYPE_NONE)
+ 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
+ // If the 'from' square is not occupied by a piece belonging to the side to
// move, the move is obviously not legal.
- if (pc == PIECE_NONE || color_of_piece(pc) != us)
+ if (pc == NO_PIECE || color_of(pc) != us)
return false;
// The destination square cannot be occupied by a friendly piece
- if (color_of_piece_on(to) == us)
+ if (pieces(us) & to)
return false;
// Handle the special case of a pawn move
- if (type_of_piece(pc) == PAWN)
+ if (type_of(pc) == PAWN)
{
- // Move direction must be compatible with pawn color
- int direction = to - from;
- if ((us == WHITE) != (direction > 0))
- return false;
-
// We have already handled promotion moves, so destination
- // cannot be on the 8/1th rank.
- if (square_rank(to) == RANK_8 || square_rank(to) == RANK_1)
- return false;
-
- // Proceed according to the square delta between the origin and
- // destination squares.
- switch (direction)
- {
- case DELTA_NW:
- case DELTA_NE:
- case DELTA_SW:
- case DELTA_SE:
- // Capture. The destination square must be occupied by an enemy
- // piece (en passant captures was handled earlier).
- if (color_of_piece_on(to) != them)
+ // cannot be on the 8th/1st rank.
+ if ((Rank8BB | Rank1BB) & to)
return false;
- // From and to files must be one file apart, avoids a7h5
- if (abs(square_file(from) - square_file(to)) != 1)
+ 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;
- break;
+ }
+ else if (!(attacks_from(type_of(pc), from) & to))
+ return false;
- case DELTA_N:
- case DELTA_S:
- // Pawn push. The destination square must be empty.
- if (!square_is_empty(to))
- return false;
- break;
-
- case DELTA_NN:
- // Double white pawn push. The destination square must be on the fourth
- // rank, and both the destination square and the square between the
- // source and destination squares must be empty.
- if ( square_rank(to) != RANK_4
- || !square_is_empty(to)
- || !square_is_empty(from + DELTA_N))
- return false;
- break;
-
- case DELTA_SS:
- // Double black pawn push. The destination square must be on the fifth
- // rank, and both the destination square and the square between the
- // source and destination squares must be empty.
- if ( square_rank(to) != RANK_5
- || !square_is_empty(to)
- || !square_is_empty(from + DELTA_S))
- return false;
- break;
+ // 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;
- default:
- 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;
}
- else if (!bit_is_set(attacks_from(pc, from), to))
- return false;
- // The move is pseudo-legal, check if it is also legal
- return in_check() ? pl_move_is_evasion(m, pinned) : pl_move_is_legal(m, pinned);
+ return true;
}
-/// Position::move_gives_check() tests whether a pseudo-legal move is a check
-
-bool Position::move_gives_check(Move m) const {
+/// Position::gives_check() tests whether a pseudo-legal move gives a check
- return move_gives_check(m, CheckInfo(*this));
-}
+bool Position::gives_check(Move m) const {
-bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
+ assert(is_ok(m));
+ assert(color_of(moved_piece(m)) == sideToMove);
- assert(is_ok());
- assert(move_is_ok(m));
- assert(ci.dcCandidates == discovered_check_candidates(side_to_move()));
- assert(color_of_piece_on(move_from(m)) == side_to_move());
- assert(piece_on(ci.ksq) == make_piece(opposite_color(side_to_move()), KING));
+ Square from = from_sq(m);
+ Square to = to_sq(m);
- Square from = move_from(m);
- Square to = move_to(m);
- PieceType pt = type_of_piece_on(from);
+ // Is there a direct check?
+ if (st->checkSquares[type_of(piece_on(from))] & to)
+ return true;
- // Direct check ?
- if (bit_is_set(ci.checkSq[pt], to))
+ // Is there a discovered check?
+ if ( (st->blockersForKing[~sideToMove] & from)
+ && !aligned(from, to, square<KING>(~sideToMove)))
return true;
- // Discovery check ?
- if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from))
+ switch (type_of(m))
{
- // For pawn and king moves we need to verify also direction
- if ( (pt != PAWN && pt != KING)
- || !squares_aligned(from, to, ci.ksq))
- return true;
- }
-
- // Can we skip the ugly special cases ?
- if (!move_is_special(m))
+ case NORMAL:
return false;
- Color us = side_to_move();
- Bitboard b = occupied_squares();
+ case PROMOTION:
+ return attacks_bb(promotion_type(m), to, pieces() ^ from) & square<KING>(~sideToMove);
- // Promotion with check ?
- if (move_is_promotion(m))
- {
- clear_bit(&b, from);
-
- switch (move_promotion_piece(m))
- {
- case KNIGHT:
- return bit_is_set(attacks_from<KNIGHT>(to), ci.ksq);
- case BISHOP:
- return bit_is_set(bishop_attacks_bb(to, b), ci.ksq);
- case ROOK:
- return bit_is_set(rook_attacks_bb(to, b), ci.ksq);
- case QUEEN:
- return bit_is_set(queen_attacks_bb(to, b), ci.ksq);
- default:
- assert(false);
- }
- }
-
- // En passant capture with check ? We have already handled the case
- // of direct checks and ordinary discovered check, the only case we
+ // 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.
- if (move_is_ep(m))
+ case ENPASSANT:
{
- Square capsq = make_square(square_file(to), square_rank(from));
- clear_bit(&b, from);
- clear_bit(&b, capsq);
- set_bit(&b, to);
- return (rook_attacks_bb(ci.ksq, b) & pieces(ROOK, QUEEN, us))
- ||(bishop_attacks_bb(ci.ksq, b) & pieces(BISHOP, QUEEN, us));
- }
+ Square capsq = make_square(file_of(to), rank_of(from));
+ Bitboard b = (pieces() ^ from ^ capsq) | to;
- // Castling with check ?
- if (move_is_castle(m))
+ 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, kto, rfrom, rto;
- kfrom = from;
- rfrom = to;
+ 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);
- if (rfrom > kfrom)
- {
- kto = relative_square(us, SQ_G1);
- rto = relative_square(us, SQ_F1);
- } else {
- kto = relative_square(us, SQ_C1);
- rto = relative_square(us, SQ_D1);
- }
- clear_bit(&b, kfrom);
- clear_bit(&b, rfrom);
- set_bit(&b, rto);
- set_bit(&b, kto);
- return bit_is_set(rook_attacks_bb(rto, b), ci.ksq);
+ return (PseudoAttacks[ROOK][rto] & square<KING>(~sideToMove))
+ && (attacks_bb<ROOK>(rto, (pieces() ^ kfrom ^ rfrom) | rto | kto) & square<KING>(~sideToMove));
+ }
+ default:
+ assert(false);
+ return false;
}
-
- return false;
-}
-
-
-/// Position::do_setup_move() makes a permanent move on the board. It should
-/// be used when setting up a position on board. You can't undo the move.
-
-void Position::do_setup_move(Move m) {
-
- StateInfo newSt;
-
- do_move(m, newSt);
-
- // Reset "game ply" in case we made a non-reversible move.
- // "game ply" is used for repetition detection.
- if (st->rule50 == 0)
- st->gamePly = 0;
-
- // Update the number of plies played from the starting position
- startPosPlyCounter++;
-
- // Our StateInfo newSt is about going out of scope so copy
- // its content before it disappears.
- detach();
}
/// 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) {
-
- CheckInfo ci(*this);
- do_move(m, newSt, ci, move_gives_check(m, ci));
-}
+void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
-void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
-
- assert(is_ok());
- assert(move_is_ok(m));
+ assert(is_ok(m));
assert(&newSt != st);
- nodes++;
- Key key = st->key;
-
- // Copy some fields of old state to our new StateInfo object except the
- // ones which are recalculated from scratch anyway, then switch our state
- // pointer to point to the new, ready to be updated, state.
- struct ReducedStateInfo {
- Key pawnKey, materialKey;
- int castleRights, rule50, gamePly, pliesFromNull;
- Square epSquare;
- Score value;
- Value npMaterial[2];
- };
-
- memcpy(&newSt, st, sizeof(ReducedStateInfo));
+ 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;
- // Save the current key to the history[] array, in order to be able to
- // detect repetition draws.
- history[st->gamePly++] = key;
+ // 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;
- // Update side to move
- key ^= zobSideToMove;
+ 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);
- // Increment the 50 moves rule draw counter. Resetting it to zero in the
- // case of non-reversible moves is taken care of later.
- st->rule50++;
- st->pliesFromNull++;
+ assert(color_of(pc) == us);
+ assert(captured == NO_PIECE || color_of(captured) == (type_of(m) != CASTLING ? them : us));
+ assert(type_of(captured) != KING);
- if (move_is_castle(m))
+ if (type_of(m) == CASTLING)
{
- st->key = key;
- do_castle_move(m);
- return;
+ 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;
}
- Color us = side_to_move();
- Color them = opposite_color(us);
- Square from = move_from(m);
- Square to = move_to(m);
- bool ep = move_is_ep(m);
- bool pm = move_is_promotion(m);
+ if (captured)
+ {
+ Square capsq = to;
- Piece piece = piece_on(from);
- PieceType pt = type_of_piece(piece);
- PieceType capture = ep ? PAWN : type_of_piece_on(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(color_of_piece_on(from) == us);
- assert(color_of_piece_on(to) == them || square_is_empty(to));
- assert(!(ep || pm) || piece == make_piece(us, PAWN));
- assert(!pm || relative_rank(us, to) == RANK_8);
+ 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));
+ }
- if (capture)
- do_capture_move(key, capture, them, to, ep);
+ st->pawnKey ^= Zobrist::psq[captured][capsq];
+ }
+ else
+ st->nonPawnMaterial[them] -= PieceValue[MG][captured];
+
+ // Update board and piece lists
+ remove_piece(capsq);
+
+ if (type_of(m) == ENPASSANT)
+ board[capsq] = NO_PIECE;
+
+ // 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]);
+
+ // Reset rule 50 counter
+ st->rule50 = 0;
+ }
// Update hash key
- key ^= zobrist[us][pt][from] ^ zobrist[us][pt][to];
+ k ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
// Reset en passant square
if (st->epSquare != SQ_NONE)
{
- key ^= zobEp[st->epSquare];
+ k ^= Zobrist::enpassant[file_of(st->epSquare)];
st->epSquare = SQ_NONE;
}
- // Update castle rights, try to shortcut a common case
- int cm = castleRightsMask[from] & castleRightsMask[to];
- if (cm != ALL_CASTLES && ((cm & st->castleRights) != st->castleRights))
+ // Update castling rights if needed
+ if (st->castlingRights && (castlingRightsMask[from] | castlingRightsMask[to]))
{
- key ^= zobCastle[st->castleRights];
- st->castleRights &= castleRightsMask[from];
- st->castleRights &= castleRightsMask[to];
- key ^= zobCastle[st->castleRights];
+ int cr = castlingRightsMask[from] | castlingRightsMask[to];
+ k ^= Zobrist::castling[st->castlingRights & cr];
+ st->castlingRights &= ~cr;
}
- // Prefetch TT access as soon as we know key is updated
- prefetch((char*)TT.first_entry(key));
-
- // Move the piece
- Bitboard move_bb = make_move_bb(from, to);
- do_move_bb(&(byColorBB[us]), move_bb);
- do_move_bb(&(byTypeBB[pt]), move_bb);
- do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
-
- board[to] = board[from];
- board[from] = PIECE_NONE;
-
- // Update piece lists, note that index[from] is not updated and
- // becomes stale. This works as long as index[] is accessed just
- // by known occupied squares.
- index[to] = index[from];
- pieceList[us][pt][index[to]] = to;
+ // Move the piece. The tricky Chess960 castling is handled earlier
+ if (type_of(m) != CASTLING)
+ move_piece(from, to);
- // If the moving piece was a pawn do some special extra work
- if (pt == PAWN)
+ // If the moving piece is a pawn do some special extra work
+ if (type_of(pc) == PAWN)
{
- // Reset rule 50 draw counter
- st->rule50 = 0;
-
- // Update pawn hash key and prefetch in L1/L2 cache
- st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
-
- // Set en passant square, only if moved pawn can be captured
- if ((to ^ from) == 16)
+ // 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)))
{
- if (attacks_from<PAWN>(from + (us == WHITE ? DELTA_N : DELTA_S), us) & pieces(PAWN, them))
- {
- st->epSquare = Square((int(from) + int(to)) / 2);
- key ^= zobEp[st->epSquare];
- }
+ st->epSquare = to - pawn_push(us);
+ k ^= Zobrist::enpassant[file_of(st->epSquare)];
}
- if (pm) // promotion ?
+ else if (type_of(m) == PROMOTION)
{
- PieceType promotion = move_promotion_piece(m);
-
- assert(promotion >= KNIGHT && promotion <= QUEEN);
-
- // Insert promoted piece instead of pawn
- clear_bit(&(byTypeBB[PAWN]), to);
- set_bit(&(byTypeBB[promotion]), to);
- board[to] = make_piece(us, promotion);
-
- // Update piece counts
- pieceCount[us][promotion]++;
- pieceCount[us][PAWN]--;
+ Piece promotion = make_piece(us, promotion_type(m));
- // Update material key
- st->materialKey ^= zobrist[us][PAWN][pieceCount[us][PAWN]];
- st->materialKey ^= zobrist[us][promotion][pieceCount[us][promotion]-1];
+ assert(relative_rank(us, to) == RANK_8);
+ assert(type_of(promotion) >= KNIGHT && type_of(promotion) <= QUEEN);
- // Update piece lists, move the last pawn at index[to] position
- // and shrink the list. Add a new promotion piece to the list.
- Square lastPawnSquare = pieceList[us][PAWN][pieceCount[us][PAWN]];
- index[lastPawnSquare] = index[to];
- pieceList[us][PAWN][index[lastPawnSquare]] = lastPawnSquare;
- pieceList[us][PAWN][pieceCount[us][PAWN]] = SQ_NONE;
- index[to] = pieceCount[us][promotion] - 1;
- pieceList[us][promotion][index[to]] = to;
+ remove_piece(to);
+ put_piece(promotion, to);
- // Partially revert hash keys update
- key ^= zobrist[us][PAWN][to] ^ zobrist[us][promotion][to];
- st->pawnKey ^= zobrist[us][PAWN][to];
-
- // Partially revert and update incremental scores
- st->value -= pst(us, PAWN, to);
- st->value += pst(us, 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 material
- st->npMaterial[us] += PieceValueMidgame[promotion];
+ st->nonPawnMaterial[us] += PieceValue[MG][promotion];
}
- }
- // Prefetch pawn and material hash tables
- Threads[threadID].pawnTable.prefetch(st->pawnKey);
- Threads[threadID].materialTable.prefetch(st->materialKey);
+ // Update pawn hash key
+ st->pawnKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
- // Update incremental scores
- st->value += pst_delta(piece, from, to);
+ // Reset rule 50 draw counter
+ st->rule50 = 0;
+ }
// Set capture piece
- st->capturedType = capture;
+ st->capturedPiece = captured;
// Update the key with the final value
- st->key = key;
+ st->key = k;
+
+ // Calculate checkers bitboard (if move gives check)
+ st->checkersBB = givesCheck ? attackers_to(square<KING>(them)) & pieces(us) : 0;
- // Update checkers bitboard, piece must be already moved
- st->checkersBB = EmptyBoardBB;
+ sideToMove = ~sideToMove;
- if (moveIsCheck)
+ // Update king attacks used for fast check detection
+ set_check_info(st);
+
+ // 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)
{
- if (ep | pm)
- st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us);
- else
+ StateInfo* stp = st->previous->previous;
+ for (int i = 4; i <= end; i += 2)
{
- // Direct checks
- if (bit_is_set(ci.checkSq[pt], to))
- st->checkersBB = SetMaskBB[to];
-
- // Discovery checks
- if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from))
+ stp = stp->previous->previous;
+ if (stp->key == st->key)
{
- if (pt != ROOK)
- st->checkersBB |= (attacks_from<ROOK>(ci.ksq) & pieces(ROOK, QUEEN, us));
-
- if (pt != BISHOP)
- st->checkersBB |= (attacks_from<BISHOP>(ci.ksq) & pieces(BISHOP, QUEEN, us));
+ st->repetition = stp->repetition ? -i : i;
+ break;
}
}
}
- // Finish
- sideToMove = opposite_color(sideToMove);
- st->value += (sideToMove == WHITE ? TempoValue : -TempoValue);
-
- assert(is_ok());
-}
-
-
-/// Position::do_capture_move() is a private method used to update captured
-/// piece info. It is called from the main Position::do_move function.
-
-void Position::do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep) {
-
- assert(capture != KING);
-
- Square capsq = to;
-
- // If the captured piece was a pawn, update pawn hash key,
- // otherwise update non-pawn material.
- if (capture == PAWN)
- {
- if (ep) // en passant ?
- {
- capsq = (them == BLACK)? (to - DELTA_N) : (to - DELTA_S);
-
- assert(to == st->epSquare);
- assert(relative_rank(opposite_color(them), to) == RANK_6);
- assert(piece_on(to) == PIECE_NONE);
- assert(piece_on(capsq) == make_piece(them, PAWN));
-
- board[capsq] = PIECE_NONE;
- }
- st->pawnKey ^= zobrist[them][PAWN][capsq];
- }
- else
- st->npMaterial[them] -= PieceValueMidgame[capture];
-
- // Remove captured piece
- clear_bit(&(byColorBB[them]), capsq);
- clear_bit(&(byTypeBB[capture]), capsq);
- clear_bit(&(byTypeBB[0]), capsq);
-
- // Update hash key
- key ^= zobrist[them][capture][capsq];
-
- // Update incremental scores
- st->value -= pst(them, capture, capsq);
-
- // Update piece count
- pieceCount[them][capture]--;
-
- // Update material hash key
- st->materialKey ^= zobrist[them][capture][pieceCount[them][capture]];
-
- // Update piece list, move the last piece at index[capsq] position
- //
- // WARNING: This is a not perfectly revresible operation. When we
- // will reinsert the captured piece in undo_move() we will put it
- // at the end of the list and not in its original place, it means
- // index[] and pieceList[] are not guaranteed to be invariant to a
- // do_move() + undo_move() sequence.
- Square lastPieceSquare = pieceList[them][capture][pieceCount[them][capture]];
- index[lastPieceSquare] = index[capsq];
- pieceList[them][capture][index[lastPieceSquare]] = lastPieceSquare;
- pieceList[them][capture][pieceCount[them][capture]] = SQ_NONE;
-
- // Reset rule 50 counter
- st->rule50 = 0;
-}
-
-
-/// Position::do_castle_move() is a private method used to make a castling
-/// move. It is called from the main Position::do_move function. Note that
-/// castling moves are encoded as "king captures friendly rook" moves, for
-/// instance white short castling in a non-Chess960 game is encoded as e1h1.
-
-void Position::do_castle_move(Move m) {
-
- assert(move_is_ok(m));
- assert(move_is_castle(m));
-
- Color us = side_to_move();
- Color them = opposite_color(us);
-
- // Reset capture field
- st->capturedType = PIECE_TYPE_NONE;
-
- // Find source squares for king and rook
- Square kfrom = move_from(m);
- Square rfrom = move_to(m); // HACK: See comment at beginning of function
- Square kto, rto;
-
- assert(piece_on(kfrom) == make_piece(us, KING));
- assert(piece_on(rfrom) == make_piece(us, ROOK));
-
- // Find destination squares for king and rook
- if (rfrom > kfrom) // O-O
- {
- kto = relative_square(us, SQ_G1);
- rto = relative_square(us, SQ_F1);
- } else { // O-O-O
- kto = relative_square(us, SQ_C1);
- rto = relative_square(us, SQ_D1);
- }
-
- // Remove pieces from source squares:
- clear_bit(&(byColorBB[us]), kfrom);
- clear_bit(&(byTypeBB[KING]), kfrom);
- clear_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares
- clear_bit(&(byColorBB[us]), rfrom);
- clear_bit(&(byTypeBB[ROOK]), rfrom);
- clear_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares
-
- // Put pieces on destination squares:
- set_bit(&(byColorBB[us]), kto);
- set_bit(&(byTypeBB[KING]), kto);
- set_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares
- set_bit(&(byColorBB[us]), rto);
- set_bit(&(byTypeBB[ROOK]), rto);
- set_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
-
- // Update board array
- Piece king = make_piece(us, KING);
- Piece rook = make_piece(us, ROOK);
- board[kfrom] = board[rfrom] = PIECE_NONE;
- board[kto] = king;
- board[rto] = rook;
-
- // Update piece lists
- pieceList[us][KING][index[kfrom]] = kto;
- pieceList[us][ROOK][index[rfrom]] = rto;
- int tmp = index[rfrom]; // In Chess960 could be rto == kfrom
- index[kto] = index[kfrom];
- index[rto] = tmp;
-
- // Update incremental scores
- st->value += pst_delta(king, kfrom, kto);
- st->value += pst_delta(rook, rfrom, rto);
-
- // Update hash key
- st->key ^= zobrist[us][KING][kfrom] ^ zobrist[us][KING][kto];
- st->key ^= zobrist[us][ROOK][rfrom] ^ zobrist[us][ROOK][rto];
-
- // Clear en passant square
- if (st->epSquare != SQ_NONE)
- {
- st->key ^= zobEp[st->epSquare];
- st->epSquare = SQ_NONE;
- }
-
- // Update castling rights
- st->key ^= zobCastle[st->castleRights];
- st->castleRights &= castleRightsMask[kfrom];
- st->key ^= zobCastle[st->castleRights];
-
- // Reset rule 50 counter
- st->rule50 = 0;
-
- // Update checkers BB
- st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us);
-
- // Finish
- sideToMove = opposite_color(sideToMove);
- st->value += (sideToMove == WHITE ? TempoValue : -TempoValue);
-
- assert(is_ok());
+ assert(pos_is_ok());
}
void Position::undo_move(Move m) {
- assert(is_ok());
- assert(move_is_ok(m));
+ assert(is_ok(m));
- sideToMove = opposite_color(sideToMove);
+ sideToMove = ~sideToMove;
- if (move_is_castle(m))
- {
- undo_castle_move(m);
- return;
- }
+ Color us = sideToMove;
+ Square from = from_sq(m);
+ Square to = to_sq(m);
+ Piece pc = piece_on(to);
- Color us = side_to_move();
- Color them = opposite_color(us);
- Square from = move_from(m);
- Square to = move_to(m);
- bool ep = move_is_ep(m);
- bool pm = move_is_promotion(m);
+ assert(empty(from) || type_of(m) == CASTLING);
+ assert(type_of(st->capturedPiece) != KING);
- PieceType pt = type_of_piece_on(to);
+ 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);
- assert(square_is_empty(from));
- assert(color_of_piece_on(to) == us);
- assert(!pm || relative_rank(us, to) == RANK_8);
- assert(!ep || to == st->previous->epSquare);
- assert(!ep || relative_rank(us, to) == RANK_6);
- assert(!ep || piece_on(to) == make_piece(us, PAWN));
+ remove_piece(to);
+ pc = make_piece(us, PAWN);
+ put_piece(pc, to);
+ }
- if (pm) // promotion ?
+ if (type_of(m) == CASTLING)
{
- PieceType promotion = move_promotion_piece(m);
- pt = PAWN;
-
- assert(promotion >= KNIGHT && promotion <= QUEEN);
- assert(piece_on(to) == make_piece(us, promotion));
-
- // Replace promoted piece with a pawn
- clear_bit(&(byTypeBB[promotion]), to);
- set_bit(&(byTypeBB[PAWN]), to);
-
- // Update piece counts
- pieceCount[us][promotion]--;
- pieceCount[us][PAWN]++;
-
- // Update piece list replacing promotion piece with a pawn
- Square lastPromotionSquare = pieceList[us][promotion][pieceCount[us][promotion]];
- index[lastPromotionSquare] = index[to];
- pieceList[us][promotion][index[lastPromotionSquare]] = lastPromotionSquare;
- pieceList[us][promotion][pieceCount[us][promotion]] = SQ_NONE;
- index[to] = pieceCount[us][PAWN] - 1;
- pieceList[us][PAWN][index[to]] = to;
+ Square rfrom, rto;
+ do_castling<false>(us, from, to, rfrom, rto);
}
-
- // Put the piece back at the source square
- Bitboard move_bb = make_move_bb(to, from);
- do_move_bb(&(byColorBB[us]), move_bb);
- do_move_bb(&(byTypeBB[pt]), move_bb);
- do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
-
- board[from] = make_piece(us, pt);
- board[to] = PIECE_NONE;
-
- // Update piece list
- index[from] = index[to];
- pieceList[us][pt][index[from]] = from;
-
- if (st->capturedType)
+ else
{
- Square capsq = to;
-
- if (ep)
- capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
-
- assert(st->capturedType != KING);
- assert(!ep || square_is_empty(capsq));
+ move_piece(to, from); // Put the piece back at the source square
- // Restore the captured piece
- set_bit(&(byColorBB[them]), capsq);
- set_bit(&(byTypeBB[st->capturedType]), capsq);
- set_bit(&(byTypeBB[0]), capsq);
+ if (st->capturedPiece)
+ {
+ Square capsq = to;
- board[capsq] = make_piece(them, st->capturedType);
+ if (type_of(m) == ENPASSANT)
+ {
+ capsq -= pawn_push(us);
- // Update piece count
- pieceCount[them][st->capturedType]++;
+ 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));
+ }
- // Update piece list, add a new captured piece in capsq square
- index[capsq] = pieceCount[them][st->capturedType] - 1;
- pieceList[them][st->capturedType][index[capsq]] = capsq;
+ put_piece(st->capturedPiece, capsq); // Restore the captured piece
+ }
}
// Finally point our state pointer back to the previous state
st = st->previous;
+ --gamePly;
- assert(is_ok());
+ assert(pos_is_ok());
}
-/// Position::undo_castle_move() is a private method used to unmake a castling
-/// move. It is called from the main Position::undo_move function. Note that
-/// castling moves are encoded as "king captures friendly rook" moves, for
-/// instance white short castling in a non-Chess960 game is encoded as e1h1.
-
-void Position::undo_castle_move(Move m) {
-
- assert(move_is_ok(m));
- assert(move_is_castle(m));
+/// 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.
+template<bool Do>
+void Position::do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto) {
- // When we have arrived here, some work has already been done by
- // Position::undo_move. In particular, the side to move has been switched,
- // so the code below is correct.
- Color us = side_to_move();
+ 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);
- // Find source squares for king and rook
- Square kfrom = move_from(m);
- Square rfrom = move_to(m); // HACK: See comment at beginning of function
- Square kto, rto;
-
- // Find destination squares for king and rook
- if (rfrom > kfrom) // O-O
- {
- kto = relative_square(us, SQ_G1);
- rto = relative_square(us, SQ_F1);
- } else { // O-O-O
- kto = relative_square(us, SQ_C1);
- rto = relative_square(us, SQ_D1);
- }
-
- assert(piece_on(kto) == make_piece(us, KING));
- assert(piece_on(rto) == make_piece(us, ROOK));
-
- // Remove pieces from destination squares:
- clear_bit(&(byColorBB[us]), kto);
- clear_bit(&(byTypeBB[KING]), kto);
- clear_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares
- clear_bit(&(byColorBB[us]), rto);
- clear_bit(&(byTypeBB[ROOK]), rto);
- clear_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
-
- // Put pieces on source squares:
- set_bit(&(byColorBB[us]), kfrom);
- set_bit(&(byTypeBB[KING]), kfrom);
- set_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares
- set_bit(&(byColorBB[us]), rfrom);
- set_bit(&(byTypeBB[ROOK]), rfrom);
- set_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares
-
- // Update board
- board[rto] = board[kto] = PIECE_NONE;
- board[rfrom] = make_piece(us, ROOK);
- board[kfrom] = make_piece(us, KING);
-
- // Update piece lists
- pieceList[us][KING][index[kto]] = kfrom;
- pieceList[us][ROOK][index[rto]] = rfrom;
- int tmp = index[rto]; // In Chess960 could be rto == kfrom
- index[kfrom] = index[kto];
- index[rfrom] = tmp;
-
- // Finally point our state pointer back to the previous state
- st = st->previous;
-
- assert(is_ok());
+ // 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; // Since remove_piece doesn't do this for us
+ put_piece(make_piece(us, KING), Do ? to : from);
+ put_piece(make_piece(us, ROOK), Do ? rto : rfrom);
}
-/// Position::do_null_move makes() a "null move": It switches the side to move
-/// and updates the hash key without executing any move on the board.
-
-void Position::do_null_move(StateInfo& backupSt) {
+/// 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.
- assert(is_ok());
- assert(!in_check());
+void Position::do_null_move(StateInfo& newSt) {
- // Back up the information necessary to undo the null move to the supplied
- // StateInfo object.
- // Note that differently from normal case here backupSt is actually used as
- // a backup storage not as a new state to be used.
- backupSt.key = st->key;
- backupSt.epSquare = st->epSquare;
- backupSt.value = st->value;
- backupSt.previous = st->previous;
- backupSt.pliesFromNull = st->pliesFromNull;
- st->previous = &backupSt;
+ assert(!checkers());
+ assert(&newSt != st);
- // Save the current key to the history[] array, in order to be able to
- // detect repetition draws.
- history[st->gamePly++] = st->key;
+ std::memcpy(&newSt, st, sizeof(StateInfo));
+ newSt.previous = st;
+ st = &newSt;
- // Update the necessary information
if (st->epSquare != SQ_NONE)
- st->key ^= zobEp[st->epSquare];
-
- st->key ^= zobSideToMove;
- prefetch((char*)TT.first_entry(st->key));
-
- sideToMove = opposite_color(sideToMove);
- st->epSquare = SQ_NONE;
- st->rule50++;
- st->pliesFromNull = 0;
- st->value += (sideToMove == WHITE) ? TempoValue : -TempoValue;
-}
-
-
-/// Position::undo_null_move() unmakes a "null move".
-
-void Position::undo_null_move() {
-
- assert(is_ok());
- assert(!in_check());
-
- // Restore information from the our backup StateInfo object
- StateInfo* backupSt = st->previous;
- st->key = backupSt->key;
- st->epSquare = backupSt->epSquare;
- st->value = backupSt->value;
- st->previous = backupSt->previous;
- st->pliesFromNull = backupSt->pliesFromNull;
-
- // Update the necessary information
- sideToMove = opposite_color(sideToMove);
- st->rule50--;
- st->gamePly--;
-}
-
-
-/// Position::see() is a static exchange evaluator: It tries to estimate the
-/// material gain or loss resulting from a move. There are three versions of
-/// this function: One which takes a destination square as input, one takes a
-/// move, and one which takes a 'from' and a 'to' square. The function does
-/// not yet understand promotions captures.
-
-int Position::see_sign(Move m) const {
-
- assert(move_is_ok(m));
-
- Square from = move_from(m);
- Square to = move_to(m);
-
- // 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 (midgame_value_of_piece_on(to) >= midgame_value_of_piece_on(from))
- return 1;
-
- return see(m);
-}
-
-int Position::see(Move m) const {
-
- Square from, to;
- Bitboard occupied, attackers, stmAttackers, b;
- int swapList[32], slIndex = 1;
- PieceType capturedType, pt;
- Color stm;
-
- assert(move_is_ok(m));
-
- // As castle moves are implemented as capturing the rook, they have
- // SEE == RookValueMidgame most of the times (unless the rook is under
- // attack).
- if (move_is_castle(m))
- return 0;
-
- from = move_from(m);
- to = move_to(m);
- capturedType = type_of_piece_on(to);
- occupied = occupied_squares();
-
- // Handle en passant moves
- if (st->epSquare == to && type_of_piece_on(from) == PAWN)
{
- Square capQq = (side_to_move() == WHITE ? to - DELTA_N : to - DELTA_S);
-
- assert(capturedType == PIECE_TYPE_NONE);
- assert(type_of_piece_on(capQq) == PAWN);
-
- // Remove the captured pawn
- clear_bit(&occupied, capQq);
- capturedType = PAWN;
+ st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
+ st->epSquare = SQ_NONE;
}
- // Find all attackers to the destination square, with the moving piece
- // removed, but possibly an X-ray attacker added behind it.
- clear_bit(&occupied, from);
- attackers = (rook_attacks_bb(to, occupied) & pieces(ROOK, QUEEN))
- | (bishop_attacks_bb(to, occupied)& pieces(BISHOP, QUEEN))
- | (attacks_from<KNIGHT>(to) & pieces(KNIGHT))
- | (attacks_from<KING>(to) & pieces(KING))
- | (attacks_from<PAWN>(to, WHITE) & pieces(PAWN, BLACK))
- | (attacks_from<PAWN>(to, BLACK) & pieces(PAWN, WHITE));
-
- // If the opponent has no attackers we are finished
- stm = opposite_color(color_of_piece_on(from));
- stmAttackers = attackers & pieces_of_color(stm);
- if (!stmAttackers)
- return seeValues[capturedType];
-
- // 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.
- swapList[0] = seeValues[capturedType];
- capturedType = type_of_piece_on(from);
-
- do {
- // Locate the least valuable attacker for the side to move. The loop
- // below looks like it is potentially infinite, but it isn't. We know
- // that the side to move still has at least one attacker left.
- for (pt = PAWN; !(stmAttackers & pieces(pt)); pt++)
- assert(pt < KING);
-
- // Remove the attacker we just found from the 'occupied' bitboard,
- // and scan for new X-ray attacks behind the attacker.
- b = stmAttackers & pieces(pt);
- occupied ^= (b & (~b + 1));
- attackers |= (rook_attacks_bb(to, occupied) & pieces(ROOK, QUEEN))
- | (bishop_attacks_bb(to, occupied) & pieces(BISHOP, QUEEN));
-
- attackers &= occupied; // Cut out pieces we've already done
-
- // Add the new entry to the swap list
- assert(slIndex < 32);
- swapList[slIndex] = -swapList[slIndex - 1] + seeValues[capturedType];
- slIndex++;
-
- // Remember the value of the capturing piece, and change the side to
- // move before beginning the next iteration.
- capturedType = pt;
- stm = opposite_color(stm);
- stmAttackers = attackers & pieces_of_color(stm);
-
- // Stop before processing a king capture
- if (capturedType == KING && stmAttackers)
- {
- assert(slIndex < 32);
- swapList[slIndex++] = QueenValueMidgame*10;
- break;
- }
- } while (stmAttackers);
-
- // 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] = Min(-swapList[slIndex], swapList[slIndex-1]);
-
- return swapList[0];
-}
+ st->key ^= Zobrist::side;
+ prefetch(TT.first_entry(st->key));
+ ++st->rule50;
+ st->pliesFromNull = 0;
-/// Position::clear() erases the position object to a pristine state, with an
-/// empty board, white to move, and no castling rights.
-
-void Position::clear() {
+ sideToMove = ~sideToMove;
- st = &startState;
- memset(st, 0, sizeof(StateInfo));
- st->epSquare = SQ_NONE;
- startPosPlyCounter = 0;
- nodes = 0;
+ set_check_info(st);
- memset(byColorBB, 0, sizeof(Bitboard) * 2);
- memset(byTypeBB, 0, sizeof(Bitboard) * 8);
- memset(pieceCount, 0, sizeof(int) * 2 * 8);
- memset(index, 0, sizeof(int) * 64);
+ st->repetition = 0;
- for (int i = 0; i < 64; i++)
- board[i] = PIECE_NONE;
+ assert(pos_is_ok());
+}
- for (int i = 0; i < 8; i++)
- for (int j = 0; j < 16; j++)
- pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
+void Position::undo_null_move() {
- for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
- castleRightsMask[sq] = ALL_CASTLES;
+ assert(!checkers());
- sideToMove = WHITE;
- initialKFile = FILE_E;
- initialKRFile = FILE_H;
- initialQRFile = FILE_A;
+ st = st->previous;
+ sideToMove = ~sideToMove;
}
-/// Position::put_piece() puts a piece on the given square of the board,
-/// updating the board array, pieces list, bitboards, and piece counts.
+/// 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.
-void Position::put_piece(Piece p, Square s) {
+Key Position::key_after(Move m) const {
- Color c = color_of_piece(p);
- PieceType pt = type_of_piece(p);
+ 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;
- board[s] = p;
- index[s] = pieceCount[c][pt]++;
- pieceList[c][pt][index[s]] = s;
+ if (captured)
+ k ^= Zobrist::psq[captured][to];
- set_bit(&(byTypeBB[pt]), s);
- set_bit(&(byColorBB[c]), s);
- set_bit(&(byTypeBB[0]), s); // HACK: byTypeBB[0] contains all occupied squares.
+ return k ^ Zobrist::psq[pc][to] ^ Zobrist::psq[pc][from];
}
-/// Position::compute_key() computes the hash key of the position. The hash
-/// key is usually updated incrementally as moves are made and unmade, the
-/// compute_key() function is only used when a new position is set up, and
-/// to verify the correctness of the hash key when running in debug mode.
+/// Position::see_ge (Static Exchange Evaluation Greater or Equal) tests if the
+/// SEE 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.
-Key Position::compute_key() const {
+bool Position::see_ge(Move m, Value threshold) const {
- Key result = zobCastle[st->castleRights];
+ assert(is_ok(m));
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- if (square_is_occupied(s))
- result ^= zobrist[color_of_piece_on(s)][type_of_piece_on(s)][s];
+ // Only deal with normal moves, assume others pass a simple see
+ if (type_of(m) != NORMAL)
+ return VALUE_ZERO >= threshold;
- if (ep_square() != SQ_NONE)
- result ^= zobEp[ep_square()];
+ Square from = from_sq(m), to = to_sq(m);
- if (side_to_move() == BLACK)
- result ^= zobSideToMove;
-
- return result;
-}
-
-
-/// Position::compute_pawn_key() computes the hash key of the position. The
-/// hash key is usually updated incrementally as moves are made and unmade,
-/// the compute_pawn_key() function is only used when a new position is set
-/// up, and to verify the correctness of the pawn hash key when running in
-/// debug mode.
+ int swap = PieceValue[MG][piece_on(to)] - threshold;
+ if (swap < 0)
+ return false;
-Key Position::compute_pawn_key() const {
+ swap = PieceValue[MG][piece_on(from)] - swap;
+ if (swap <= 0)
+ return true;
- Bitboard b;
- Key result = 0;
+ Bitboard occupied = pieces() ^ from ^ to;
+ Color stm = color_of(piece_on(from));
+ Bitboard attackers = attackers_to(to, occupied);
+ Bitboard stmAttackers, bb;
+ int res = 1;
- for (Color c = WHITE; c <= BLACK; c++)
+ while (true)
{
- b = pieces(PAWN, c);
- while (b)
- result ^= zobrist[c][PAWN][pop_1st_bit(&b)];
- }
- return result;
-}
+ stm = ~stm;
+ attackers &= occupied;
+ // If stm has no more attackers then give up: stm loses
+ if (!(stmAttackers = attackers & pieces(stm)))
+ break;
-/// Position::compute_material_key() computes the hash key of the position.
-/// The hash key is usually updated incrementally as moves are made and unmade,
-/// the compute_material_key() function is only used when a new position is set
-/// up, and to verify the correctness of the material hash key when running in
-/// debug mode.
+ // Don't allow pinned pieces to attack (except the king) as long as
+ // there are pinners on their original square.
+ if (st->pinners[~stm] & occupied)
+ stmAttackers &= ~st->blockersForKing[stm];
-Key Position::compute_material_key() const {
+ if (!stmAttackers)
+ break;
- int count;
- Key result = 0;
+ res ^= 1;
- for (Color c = WHITE; c <= BLACK; c++)
- for (PieceType pt = PAWN; pt <= QUEEN; pt++)
+ // 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)))
{
- count = piece_count(c, pt);
- for (int i = 0; i < count; i++)
- result ^= zobrist[c][pt][i];
- }
- return result;
-}
+ if ((swap = PawnValueMg - swap) < res)
+ break;
+ occupied ^= lsb(bb);
+ attackers |= attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN);
+ }
-/// Position::compute_value() compute the incremental scores for the middle
-/// game and the endgame. These functions are used to initialize the incremental
-/// scores when a new position is set up, and to verify that the scores are correctly
-/// updated by do_move and undo_move when the program is running in debug mode.
-Score Position::compute_value() const {
+ else if ((bb = stmAttackers & pieces(KNIGHT)))
+ {
+ if ((swap = KnightValueMg - swap) < res)
+ break;
- Bitboard b;
- Score result = SCORE_ZERO;
+ occupied ^= lsb(bb);
+ }
- for (Color c = WHITE; c <= BLACK; c++)
- for (PieceType pt = PAWN; pt <= KING; pt++)
+ else if ((bb = stmAttackers & pieces(BISHOP)))
{
- b = pieces(pt, c);
- while (b)
- result += pst(c, pt, pop_1st_bit(&b));
- }
+ if ((swap = BishopValueMg - swap) < res)
+ break;
- result += (side_to_move() == WHITE ? TempoValue / 2 : -TempoValue / 2);
- return result;
-}
+ occupied ^= lsb(bb);
+ attackers |= attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN);
+ }
+ else if ((bb = stmAttackers & pieces(ROOK)))
+ {
+ if ((swap = RookValueMg - swap) < res)
+ break;
-/// Position::compute_non_pawn_material() computes the total non-pawn middle
-/// game material value for the given side. Material values are updated
-/// incrementally during the search, this function is only used while
-/// initializing a new Position object.
+ occupied ^= lsb(bb);
+ attackers |= attacks_bb<ROOK>(to, occupied) & pieces(ROOK, QUEEN);
+ }
-Value Position::compute_non_pawn_material(Color c) const {
+ else if ((bb = stmAttackers & pieces(QUEEN)))
+ {
+ if ((swap = QueenValueMg - swap) < res)
+ break;
- Value result = VALUE_ZERO;
+ occupied ^= lsb(bb);
+ attackers |= (attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN))
+ | (attacks_bb<ROOK >(to, occupied) & pieces(ROOK , QUEEN));
+ }
- for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
- result += piece_count(c, pt) * PieceValueMidgame[pt];
+ else // KING
+ // If we "capture" with the king but opponent still has attackers,
+ // reverse the result.
+ return (attackers & ~pieces(stm)) ? res ^ 1 : res;
+ }
- return result;
+ return bool(res);
}
+/// Position::is_draw() tests whether the position is drawn by 50-move rule
+/// or by repetition. It does not detect stalemates.
-/// Position::is_draw() tests whether the position is drawn by material,
-/// repetition, or the 50 moves rule. It does not detect stalemates, this
-/// must be done by the search.
-
-bool Position::is_draw() const {
+bool Position::is_draw(int ply) const {
- // Draw by material?
- if ( !pieces(PAWN)
- && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMidgame))
+ if (st->rule50 > 99 && (!checkers() || MoveList<LEGAL>(*this).size()))
return true;
- // Draw by the 50 moves rule?
- if (st->rule50 > 99 && !is_mate())
+ // Return a draw score if a position repeats once earlier but strictly
+ // after the root, or repeats twice before or at the root.
+ if (st->repetition && st->repetition < ply)
return true;
- // Draw by repetition?
- for (int i = 4, e = Min(Min(st->gamePly, st->rule50), st->pliesFromNull); i <= e; i += 2)
- if (history[st->gamePly - i] == st->key)
- return true;
-
return false;
}
-/// Position::is_mate() returns true or false depending on whether the
-/// side to move is checkmated.
+// Position::has_repeated() tests whether there has been at least one repetition
+// of positions since the last capture or pawn move.
-bool Position::is_mate() const {
+bool Position::has_repeated() const {
- MoveStack moves[MAX_MOVES];
- return in_check() && generate<MV_LEGAL>(*this, moves) == moves;
-}
-
-
-/// Position::init_zobrist() is a static member function which initializes at
-/// startup the various arrays used to compute hash keys.
+ StateInfo* stc = st;
+ int end = std::min(st->rule50, st->pliesFromNull);
+ while (end-- >= 4)
+ {
+ if (stc->repetition)
+ return true;
-void Position::init_zobrist() {
+ stc = stc->previous;
+ }
+ return false;
+}
- int i,j, k;
- RKISS rk;
- for (i = 0; i < 2; i++) for (j = 0; j < 8; j++) for (k = 0; k < 64; k++)
- zobrist[i][j][k] = rk.rand<Key>();
+/// Position::has_game_cycle() tests if the position has a move which draws by repetition,
+/// or an earlier position has a move that directly reaches the current position.
- for (i = 0; i < 64; i++)
- zobEp[i] = rk.rand<Key>();
+bool Position::has_game_cycle(int ply) const {
- for (i = 0; i < 16; i++)
- zobCastle[i] = rk.rand<Key>();
+ int j;
- zobSideToMove = rk.rand<Key>();
- zobExclusion = rk.rand<Key>();
-}
+ int end = std::min(st->rule50, st->pliesFromNull);
+ if (end < 3)
+ return false;
-/// Position::init_piece_square_tables() initializes the piece square tables.
-/// This is a two-step operation: First, the white halves of the tables are
-/// copied from the MgPST[][] and EgPST[][] arrays. Second, the black halves
-/// of the tables are initialized by mirroring and changing the sign of the
-/// corresponding white scores.
+ Key originalKey = st->key;
+ StateInfo* stp = st->previous;
-void Position::init_piece_square_tables() {
+ for (int i = 3; i <= end; i += 2)
+ {
+ stp = stp->previous->previous;
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- for (Piece p = WP; p <= WK; p++)
- PieceSquareTable[p][s] = make_score(MgPST[p][s], EgPST[p][s]);
+ 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);
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- for (Piece p = BP; p <= BK; p++)
- PieceSquareTable[p][s] = -PieceSquareTable[p-8][flip_square(s)];
+ if (!(between_bb(s1, 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;
}
/// Position::flip() flips position with the white and black sides reversed. This
-/// is only useful for debugging especially for finding evaluation symmetry bugs.
+/// is only useful for debugging e.g. for finding evaluation symmetry bugs.
void Position::flip() {
- assert(is_ok());
-
- // Make a copy of current position before to start changing
- const Position pos(*this, threadID);
-
- clear();
- threadID = pos.thread();
-
- // Board
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- if (!pos.square_is_empty(s))
- put_piece(Piece(pos.piece_on(s) ^ 8), flip_square(s));
-
- // Side to move
- sideToMove = opposite_color(pos.side_to_move());
-
- // Castling rights
- if (pos.can_castle_kingside(WHITE)) do_allow_oo(BLACK);
- if (pos.can_castle_queenside(WHITE)) do_allow_ooo(BLACK);
- if (pos.can_castle_kingside(BLACK)) do_allow_oo(WHITE);
- if (pos.can_castle_queenside(BLACK)) do_allow_ooo(WHITE);
+ string f, token;
+ std::stringstream ss(fen());
- initialKFile = pos.initialKFile;
- initialKRFile = pos.initialKRFile;
- initialQRFile = pos.initialQRFile;
+ for (Rank r = RANK_8; r >= RANK_1; --r) // Piece placement
+ {
+ std::getline(ss, token, r > RANK_1 ? '/' : ' ');
+ f.insert(0, token + (f.empty() ? " " : "/"));
+ }
- castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO | WHITE_OOO);
- castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO | BLACK_OOO);
- castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO;
- castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO;
- castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO;
- castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO;
+ ss >> token; // Active color
+ f += (token == "w" ? "B " : "W "); // Will be lowercased later
- // En passant square
- if (pos.st->epSquare != SQ_NONE)
- st->epSquare = flip_square(pos.st->epSquare);
+ ss >> token; // Castling availability
+ f += token + " ";
- // Checkers
- find_checkers();
+ std::transform(f.begin(), f.end(), f.begin(),
+ [](char c) { return char(islower(c) ? toupper(c) : tolower(c)); });
- // Hash keys
- st->key = compute_key();
- st->pawnKey = compute_pawn_key();
- st->materialKey = compute_material_key();
+ ss >> token; // En passant square
+ f += (token == "-" ? token : token.replace(1, 1, token[1] == '3' ? "6" : "3"));
- // Incremental scores
- st->value = compute_value();
+ std::getline(ss, token); // Half and full moves
+ f += token;
- // Material
- st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
- st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
+ set(f, is_chess960(), st, this_thread());
- assert(is_ok());
+ assert(pos_is_ok());
}
-/// Position::is_ok() performs some consitency checks for the position object.
+/// Position::pos_is_ok() performs some consistency checks for the
+/// position object and raises an asserts if something wrong is detected.
/// This is meant to be helpful when debugging.
-bool Position::is_ok(int* failedStep) const {
-
- // What features of the position should be verified?
- const bool debugAll = false;
+bool Position::pos_is_ok() const {
- const bool debugBitboards = debugAll || false;
- const bool debugKingCount = debugAll || false;
- const bool debugKingCapture = debugAll || false;
- const bool debugCheckerCount = debugAll || false;
- const bool debugKey = debugAll || false;
- const bool debugMaterialKey = debugAll || false;
- const bool debugPawnKey = debugAll || false;
- const bool debugIncrementalEval = debugAll || false;
- const bool debugNonPawnMaterial = debugAll || false;
- const bool debugPieceCounts = debugAll || false;
- const bool debugPieceList = debugAll || false;
- const bool debugCastleSquares = debugAll || false;
+ constexpr bool Fast = true; // Quick (default) or full check?
- if (failedStep) *failedStep = 1;
+ 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");
- // Side to move OK?
- if (!color_is_ok(side_to_move()))
- return false;
-
- // Are the king squares in the position correct?
- if (failedStep) (*failedStep)++;
- if (piece_on(king_square(WHITE)) != WK)
- return false;
-
- if (failedStep) (*failedStep)++;
- if (piece_on(king_square(BLACK)) != BK)
- return false;
-
- // Castle files OK?
- if (failedStep) (*failedStep)++;
- if (!file_is_ok(initialKRFile))
- return false;
-
- if (!file_is_ok(initialQRFile))
- return false;
-
- // Do both sides have exactly one king?
- if (failedStep) (*failedStep)++;
- if (debugKingCount)
- {
- int kingCount[2] = {0, 0};
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- if (type_of_piece_on(s) == KING)
- kingCount[color_of_piece_on(s)]++;
-
- if (kingCount[0] != 1 || kingCount[1] != 1)
- return false;
- }
-
- // Can the side to move capture the opponent's king?
- if (failedStep) (*failedStep)++;
- if (debugKingCapture)
- {
- Color us = side_to_move();
- Color them = opposite_color(us);
- Square ksq = king_square(them);
- if (attackers_to(ksq) & pieces_of_color(us))
- return false;
- }
-
- // Is there more than 2 checkers?
- if (failedStep) (*failedStep)++;
- if (debugCheckerCount && count_1s<CNT32>(st->checkersBB) > 2)
- return false;
-
- // Bitboards OK?
- if (failedStep) (*failedStep)++;
- if (debugBitboards)
- {
- // The intersection of the white and black pieces must be empty
- if ((pieces_of_color(WHITE) & pieces_of_color(BLACK)) != EmptyBoardBB)
- return false;
-
- // The union of the white and black pieces must be equal to all
- // occupied squares
- if ((pieces_of_color(WHITE) | pieces_of_color(BLACK)) != occupied_squares())
- return false;
-
- // Separate piece type bitboards must have empty intersections
- for (PieceType p1 = PAWN; p1 <= KING; p1++)
- for (PieceType p2 = PAWN; p2 <= KING; p2++)
- if (p1 != p2 && (pieces(p1) & pieces(p2)))
- return false;
- }
-
- // En passant square OK?
- if (failedStep) (*failedStep)++;
- if (ep_square() != SQ_NONE)
- {
- // The en passant square must be on rank 6, from the point of view of the
- // side to move.
- if (relative_rank(side_to_move(), ep_square()) != RANK_6)
- return false;
- }
-
- // Hash key OK?
- if (failedStep) (*failedStep)++;
- if (debugKey && st->key != compute_key())
- return false;
-
- // Pawn hash key OK?
- if (failedStep) (*failedStep)++;
- if (debugPawnKey && st->pawnKey != compute_pawn_key())
- return false;
-
- // Material hash key OK?
- if (failedStep) (*failedStep)++;
- if (debugMaterialKey && st->materialKey != compute_material_key())
- return false;
-
- // Incremental eval OK?
- if (failedStep) (*failedStep)++;
- if (debugIncrementalEval && st->value != compute_value())
- return false;
+ if (Fast)
+ return true;
- // Non-pawn material OK?
- if (failedStep) (*failedStep)++;
- if (debugNonPawnMaterial)
+ 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");
+
+ StateInfo si = *st;
+ set_state(&si);
+ if (std::memcmp(&si, st, sizeof(StateInfo)))
+ assert(0 && "pos_is_ok: State");
+
+ for (Piece pc : Pieces)
{
- if (st->npMaterial[WHITE] != compute_non_pawn_material(WHITE))
- return false;
+ 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");
- if (st->npMaterial[BLACK] != compute_non_pawn_material(BLACK))
- return false;
+ for (int i = 0; i < pieceCount[pc]; ++i)
+ if (board[pieceList[pc][i]] != pc || index[pieceList[pc][i]] != i)
+ assert(0 && "pos_is_ok: Index");
}
- // Piece counts OK?
- if (failedStep) (*failedStep)++;
- if (debugPieceCounts)
- for (Color c = WHITE; c <= BLACK; c++)
- for (PieceType pt = PAWN; pt <= KING; pt++)
- if (pieceCount[c][pt] != count_1s<CNT32>(pieces(pt, c)))
- return false;
-
- if (failedStep) (*failedStep)++;
- if (debugPieceList)
- for (Color c = WHITE; c <= BLACK; c++)
- for (PieceType pt = PAWN; pt <= KING; pt++)
- for (int i = 0; i < pieceCount[c][pt]; i++)
- {
- if (piece_on(piece_list(c, pt, i)) != make_piece(c, pt))
- return false;
-
- if (index[piece_list(c, pt, i)] != i)
- return false;
- }
-
- if (failedStep) (*failedStep)++;
- if (debugCastleSquares)
- {
- for (Color c = WHITE; c <= BLACK; c++)
+ for (Color c : { WHITE, BLACK })
+ for (CastlingRights cr : {c & KING_SIDE, c & QUEEN_SIDE})
{
- if (can_castle_kingside(c) && piece_on(initial_kr_square(c)) != make_piece(c, ROOK))
- return false;
+ if (!can_castle(cr))
+ continue;
- if (can_castle_queenside(c) && piece_on(initial_qr_square(c)) != make_piece(c, ROOK))
- return false;
+ 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");
}
- if (castleRightsMask[initial_kr_square(WHITE)] != (ALL_CASTLES ^ WHITE_OO))
- return false;
- if (castleRightsMask[initial_qr_square(WHITE)] != (ALL_CASTLES ^ WHITE_OOO))
- return false;
- if (castleRightsMask[initial_kr_square(BLACK)] != (ALL_CASTLES ^ BLACK_OO))
- return false;
- if (castleRightsMask[initial_qr_square(BLACK)] != (ALL_CASTLES ^ BLACK_OOO))
- return false;
- }
- if (failedStep) *failedStep = 0;
return true;
}