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position.cpp
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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2022 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <algorithm>
#include <cassert>
#include <cstddef> // For offsetof()
#include <cstring> // For std::memset, std::memcmp
#include <iomanip>
#include <sstream>
#include "bitboard.h"
#include "misc.h"
#include "movegen.h"
#include "position.h"
#include "thread.h"
#include "tt.h"
#include "uci.h"
#include "syzygy/tbprobe.h"
using std::string;
namespace Stockfish {
namespace Zobrist {
Key psq[PIECE_NB][SQUARE_NB];
Key enpassant[FILE_NB];
Key castling[CASTLING_RIGHT_NB];
Key side, noPawns;
Key inHand[PIECE_NB][SQUARE_NB];
Key checks[COLOR_NB][CHECKS_NB];
Key wall[SQUARE_NB];
Key endgame[EG_EVAL_NB];
}
/// operator<<(Position) returns an ASCII representation of the position
std::ostream& operator<<(std::ostream& os, const Position& pos) {
os << "\n ";
for (File f = FILE_A; f <= pos.max_file(); ++f)
os << "+---";
os << "+\n";
for (Rank r = pos.max_rank(); r >= RANK_1; --r)
{
for (File f = FILE_A; f <= pos.max_file(); ++f)
if (pos.state()->wallSquares & make_square(f, r))
os << " | *";
else if (pos.unpromoted_piece_on(make_square(f, r)))
os << " |+" << pos.piece_to_char()[pos.unpromoted_piece_on(make_square(f, r))];
else
os << " | " << pos.piece_to_char()[pos.piece_on(make_square(f, r))];
os << " |" << (1 + r);
if (r == pos.max_rank() || r == RANK_1)
{
Color c = r == RANK_1 ? WHITE : BLACK;
if (c == pos.side_to_move())
os << " *";
else
os << " ";
if (!pos.variant()->freeDrops && (pos.piece_drops() || pos.seirawan_gating()))
{
os << " [";
for (PieceType pt = KING; pt >= PAWN; --pt)
os << std::string(pos.count_in_hand(c, pt), pos.piece_to_char()[make_piece(c, pt)]);
os << "]";
}
}
os << "\n ";
for (File f = FILE_A; f <= pos.max_file(); ++f)
os << "+---";
os << "+\n";
}
for (File f = FILE_A; f <= pos.max_file(); ++f)
os << " " << char('a' + f);
os << "\n";
os << "\nFen: " << pos.fen() << "\nSfen: " << pos.fen(true) << "\nKey: " << std::hex << std::uppercase
<< std::setfill('0') << std::setw(16) << pos.key()
<< std::setfill(' ') << std::dec << "\nCheckers: ";
for (Bitboard b = pos.checkers(); b; )
os << UCI::square(pos, pop_lsb(b)) << " ";
os << "\nChased: ";
for (Bitboard b = pos.state()->chased; b; )
os << UCI::square(pos, pop_lsb(b)) << " ";
if ( int(Tablebases::MaxCardinality) >= popcount(pos.pieces())
&& Options["UCI_Variant"] == "chess"
&& !pos.can_castle(ANY_CASTLING))
{
StateInfo st;
ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
Position p;
p.set(pos.variant(), 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 << ")";
}
return os;
}
// 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
#ifdef LARGEBOARDS
inline int H1(Key h) { return h & 0x7fff; }
inline int H2(Key h) { return (h >> 16) & 0x7fff; }
#else
inline int H1(Key h) { return h & 0x1fff; }
inline int H2(Key h) { return (h >> 16) & 0x1fff; }
#endif
// Cuckoo tables with Zobrist hashes of valid reversible moves, and the moves themselves
#ifdef LARGEBOARDS
Key cuckoo[65536];
Move cuckooMove[65536];
#else
Key cuckoo[8192];
Move cuckooMove[8192];
#endif
/// Position::init() initializes at startup the various arrays used to compute hash keys
void Position::init() {
PRNG rng(1070372);
for (Color c : {WHITE, BLACK})
for (PieceType pt = PAWN; pt <= KING; ++pt)
for (Square s = SQ_A1; s <= SQ_MAX; ++s)
Zobrist::psq[make_piece(c, pt)][s] = rng.rand<Key>();
for (File f = FILE_A; f <= FILE_MAX; ++f)
Zobrist::enpassant[f] = rng.rand<Key>();
for (int cr = NO_CASTLING; cr <= ANY_CASTLING; ++cr)
Zobrist::castling[cr] = rng.rand<Key>();
Zobrist::side = rng.rand<Key>();
Zobrist::noPawns = rng.rand<Key>();
for (Color c : {WHITE, BLACK})
for (int n = 0; n < CHECKS_NB; ++n)
Zobrist::checks[c][n] = rng.rand<Key>();
for (Color c : {WHITE, BLACK})
for (PieceType pt = PAWN; pt <= KING; ++pt)
for (int n = 0; n < SQUARE_NB; ++n)
Zobrist::inHand[make_piece(c, pt)][n] = rng.rand<Key>();
for (Square s = SQ_A1; s <= SQ_MAX; ++s)
Zobrist::wall[s] = rng.rand<Key>();
for (int i = NO_EG_EVAL; i < EG_EVAL_NB; ++i)
Zobrist::endgame[i] = rng.rand<Key>();
// Prepare the cuckoo tables
std::memset(cuckoo, 0, sizeof(cuckoo));
std::memset(cuckooMove, 0, sizeof(cuckooMove));
int count = 0;
for (Color c : {WHITE, BLACK})
for (PieceSet ps = CHESS_PIECES & ~piece_set(PAWN); ps;)
{
Piece pc = make_piece(c, pop_lsb(ps));
for (Square s1 = SQ_A1; s1 <= SQ_MAX; ++s1)
for (Square s2 = Square(s1 + 1); s2 <= SQ_MAX; ++s2)
if ((type_of(pc) != PAWN) && (attacks_bb(c, type_of(pc), s1, 0) & s2))
{
Move move = make_move(s1, s2);
Key key = Zobrist::psq[pc][s1] ^ Zobrist::psq[pc][s2] ^ Zobrist::side;
int i = H1(key);
while (true)
{
std::swap(cuckoo[i], key);
std::swap(cuckooMove[i], move);
if (move == MOVE_NONE) // Arrived at empty slot?
break;
i = (i == H1(key)) ? H2(key) : H1(key); // Push victim to alternative slot
}
count++;
}
}
#ifdef LARGEBOARDS
assert(count == 9344);
#else
assert(count == 3668);
#endif
}
Key Position::material_key(EndgameEval e) const {
return st->materialKey ^ Zobrist::endgame[e];
}
/// 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.
Position& Position::set(const Variant* v, const string& fenStr, bool isChess960, StateInfo* si, Thread* th, bool sfen) {
/*
A FEN string defines a particular position using only the ASCII character set.
A FEN string contains six fields separated by a space. The fields are:
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).
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. Following X-FEN standard, this is recorded only
if there is a pawn in position to make an en passant capture, and if there really
is a pawn that might have advanced two squares.
5) Halfmove clock. This is the number of halfmoves since the last pawn advance
or capture. This is used to determine if a draw can be claimed under the
fifty-move rule.
6) Fullmove number. The number of the full move. It starts at 1, and is
incremented after Black's move.
*/
unsigned char col, row, token;
size_t idx;
std::istringstream ss(fenStr);
std::memset(this, 0, sizeof(Position));
std::memset(si, 0, sizeof(StateInfo));
st = si;
var = v;
ss >> std::noskipws;
Rank r = max_rank();
Square sq = SQ_A1 + r * NORTH;
// 1. Piece placement
while ((ss >> token) && !isspace(token))
{
if (isdigit(token))
{
#ifdef LARGEBOARDS
if (isdigit(ss.peek()))
{
sq += 10 * (token - '0') * EAST;
ss >> token;
}
#endif
sq += (token - '0') * EAST; // Advance the given number of files
}
else if (token == '/')
{
sq = SQ_A1 + --r * NORTH;
if (!is_ok(sq))
break;
}
// Stop before pieces in hand
else if (token == '[')
break;
// Ignore pieces outside the board and wait for next / or [ to return to a valid state
else if (!is_ok(sq) || file_of(sq) > max_file() || rank_of(sq) > r)
continue;
// Wall square
else if (token == '*')
{
st->wallSquares |= sq;
byTypeBB[ALL_PIECES] |= sq;
++sq;
}
else if ((idx = piece_to_char().find(token)) != string::npos || (idx = piece_to_char_synonyms().find(token)) != string::npos)
{
if (ss.peek() == '~')
ss >> token;
put_piece(Piece(idx), sq, token == '~');
++sq;
}
// Promoted shogi pieces
else if (token == '+' && (idx = piece_to_char().find(ss.peek())) != string::npos && promoted_piece_type(type_of(Piece(idx))))
{
ss >> token;
put_piece(make_piece(color_of(Piece(idx)), promoted_piece_type(type_of(Piece(idx)))), sq, true, Piece(idx));
++sq;
}
}
// Pieces in hand
if (!isspace(token))
while ((ss >> token) && !isspace(token))
{
if (token == ']')
continue;
else if ((idx = piece_to_char().find(token)) != string::npos)
add_to_hand(Piece(idx));
}
// 2. Active color
ss >> token;
sideToMove = (token != (sfen ? 'w' : 'b') ? WHITE : BLACK); // Invert colors for SFEN
ss >> token;
// 3-4. Skip parsing castling and en passant flags if not present
st->epSquares = 0;
st->castlingKingSquare[WHITE] = st->castlingKingSquare[BLACK] = SQ_NONE;
if (!isdigit(ss.peek()) && !sfen)
{
// 3. Castling availability. Compatible with 3 standards: Normal FEN standard,
// Shredder-FEN that uses the letters of the columns on which the rooks began
// the game instead of KQkq and also X-FEN standard that, in case of Chess960,
// if an inner rook is associated with the castling right, the castling tag is
// replaced by the file letter of the involved rook, as for the Shredder-FEN.
while ((ss >> token) && !isspace(token))
{
Square rsq;
Color c = islower(token) ? BLACK : WHITE;
token = char(toupper(token));
if (castling_enabled() && token == 'K')
for (rsq = make_square(var->castlingRookKingsideFile, castling_rank(c)); (!(castling_rook_pieces(c) & type_of(piece_on(rsq))) || color_of(piece_on(rsq)) != c) && file_of(rsq) > FILE_A; --rsq) {}
else if (castling_enabled() && token == 'Q')
for (rsq = make_square(var->castlingRookQueensideFile, castling_rank(c)); (!(castling_rook_pieces(c) & type_of(piece_on(rsq))) || color_of(piece_on(rsq)) != c) && file_of(rsq) < max_file(); ++rsq) {}
else if (token >= 'A' && token <= 'A' + max_file())
rsq = make_square(File(token - 'A'), castling_rank(c));
else
continue;
// Determine castling "king" position
if (castling_enabled() && st->castlingKingSquare[c] == SQ_NONE)
{
Bitboard castlingKings = pieces(c, castling_king_piece(c)) & rank_bb(castling_rank(c));
// Ambiguity resolution for 960 variants with more than one "king"
// e.g., EAH means that an e-file king can castle with a- and h-file rooks
st->castlingKingSquare[c] = isChess960 && piece_on(rsq) == make_piece(c, castling_king_piece(c)) ? rsq
: castlingKings && (!more_than_one(castlingKings) || isChess960) ? lsb(castlingKings)
: make_square(castling_king_file(), castling_rank(c));
// Skip invalid castling rights
if (!(castlingKings & st->castlingKingSquare[c]))
st->castlingKingSquare[c] = SQ_NONE;
}
// Set gates (and skip castling rights)
if (gating())
{
// Only add gates for occupied squares
if (pieces(c) & rsq)
st->gatesBB[c] |= rsq;
if ((token == 'K' || token == 'Q') && st->castlingKingSquare[c] != SQ_NONE)
st->gatesBB[c] |= st->castlingKingSquare[c];
// Do not set castling rights for gates unless there are no pieces in hand,
// which means that the file is referring to a chess960 castling right.
else if (!seirawan_gating() || count_in_hand(c, ALL_PIECES) > 0 || captures_to_hand())
continue;
}
// Only add castling right if both king and rook are on expected squares
if ( castling_enabled()
&& st->castlingKingSquare[c] != SQ_NONE
&& (castling_rook_pieces(c) & type_of(piece_on(rsq))) && color_of(piece_on(rsq)) == c)
set_castling_right(c, rsq);
}
// Set castling rights for 960 gating variants
if (gating() && castling_enabled())
for (Color c : {WHITE, BLACK})
if ((gates(c) & pieces(castling_king_piece(c))) && !castling_rights(c) && (!seirawan_gating() || count_in_hand(c, ALL_PIECES) > 0 || captures_to_hand()))
{
Bitboard castling_rooks = gates(c) & pieces(c);
while (castling_rooks)
{
Square s = pop_lsb(castling_rooks);
if (castling_rook_pieces(c) & type_of(piece_on(s)))
set_castling_right(c, s);
}
}
// counting limit
if (counting_rule() && isdigit(ss.peek()))
ss >> st->countingLimit;
// 4. En passant square.
// Ignore if square is invalid or not on side to move relative rank 6.
else
while ( ((ss >> col) && (col >= 'a' && col <= 'a' + max_file()))
&& ((ss >> row) && (row >= '1' && row <= '1' + max_rank())))
{
Square epSquare = make_square(File(col - 'a'), Rank(row - '1'));
#ifdef LARGEBOARDS
// Consider different rank numbering in CECP
if (max_rank() == RANK_10 && CurrentProtocol == XBOARD)
epSquare += NORTH;
#endif
// En passant square will be considered only if
// epSquare is within enPassantRegion and
// 1) variant has non-standard rules
// or
// 2)
// a) side to move have a pawn threatening epSquare
// b) there is an enemy pawn one or two (for triple steps) squares in front of epSquare
// c) there is no (non-wall) piece on epSquare or behind epSquare
if ( (var->enPassantRegion & epSquare)
&& ( !var->fastAttacks
|| (var->enPassantTypes[sideToMove] & ~piece_set(PAWN))
|| ( pawn_attacks_bb(~sideToMove, epSquare) & pieces(sideToMove, PAWN)
&& ( (pieces(~sideToMove, PAWN) & (epSquare + pawn_push(~sideToMove)))
|| (pieces(~sideToMove, PAWN) & (epSquare + 2 * pawn_push(~sideToMove))))
&& !((pieces(WHITE) | pieces(BLACK)) & (epSquare | (epSquare + pawn_push(sideToMove)))))))
st->epSquares |= epSquare;
}
}
// Check counter for nCheck
ss >> std::skipws >> token >> std::noskipws;
if (check_counting())
{
if (ss.peek() == '+')
{
st->checksRemaining[WHITE] = CheckCount(std::max(token - '0', 0));
ss >> token >> token;
st->checksRemaining[BLACK] = CheckCount(std::max(token - '0', 0));
}
else
{
// If check count is not provided, assume that the next check wins
st->checksRemaining[WHITE] = CheckCount(1);
st->checksRemaining[BLACK] = CheckCount(1);
ss.putback(token);
}
}
else
ss.putback(token);
// 5-6. Halfmove clock and fullmove number
if (sfen)
{
// Pieces in hand for SFEN
int handCount = 1;
while ((ss >> token) && !isspace(token))
{
if (token == '-')
continue;
else if (isdigit(token))
{
handCount = token - '0';
while (isdigit(ss.peek()) && ss >> token)
handCount = 10 * handCount + (token - '0');
}
else if ((idx = piece_to_char().find(token)) != string::npos)
{
for (int i = 0; i < handCount; i++)
add_to_hand(Piece(idx));
handCount = 1;
}
}
// Move count is in ply for SFEN
ss >> std::skipws >> gamePly;
gamePly = std::max(gamePly - 1, 0);
}
else
{
ss >> std::skipws >> st->rule50 >> gamePly;
// Convert from fullmove starting from 1 to gamePly starting from 0,
// handle also common incorrect FEN with fullmove = 0.
gamePly = std::max(2 * (gamePly - 1), 0) + (sideToMove == BLACK);
}
// counting rules
if (st->countingLimit && st->rule50)
{
st->countingPly = st->rule50;
st->rule50 = 0;
}
// Lichess-style counter for 3check
if (check_counting())
{
if (ss >> token && token == '+')
{
ss >> token;
st->checksRemaining[WHITE] = CheckCount(std::max(3 - (token - '0'), 0));
ss >> token >> token;
st->checksRemaining[BLACK] = CheckCount(std::max(3 - (token - '0'), 0));
}
}
chess960 = isChess960 || v->chess960;
tsumeMode = Options["TsumeMode"];
thisThread = th;
set_state(st);
assert(pos_is_ok());
return *this;
}
/// Position::set_castling_right() is a helper function used to set castling
/// rights given the corresponding color and the rook starting square.
void Position::set_castling_right(Color c, Square rfrom) {
assert(st->castlingKingSquare[c] != SQ_NONE);
Square kfrom = st->castlingKingSquare[c];
CastlingRights cr = c & (kfrom < rfrom ? KING_SIDE: QUEEN_SIDE);
st->castlingRights |= cr;
castlingRightsMask[kfrom] |= cr;
castlingRightsMask[rfrom] |= cr;
castlingRookSquare[cr] = rfrom;
Square kto = make_square(cr & KING_SIDE ? castling_kingside_file() : castling_queenside_file(), castling_rank(c));
Square rto = kto + (cr & KING_SIDE ? WEST : EAST);
castlingPath[cr] = (between_bb(rfrom, rto) | between_bb(kfrom, kto))
& ~(kfrom | rfrom);
}
/// Position::set_check_info() sets king attacks to detect if a move gives check
void Position::set_check_info(StateInfo* si) const {
si->blockersForKing[WHITE] = slider_blockers(pieces(BLACK), count<KING>(WHITE) ? square<KING>(WHITE) : SQ_NONE, si->pinners[BLACK], BLACK);
si->blockersForKing[BLACK] = slider_blockers(pieces(WHITE), count<KING>(BLACK) ? square<KING>(BLACK) : SQ_NONE, si->pinners[WHITE], WHITE);
Square ksq = count<KING>(~sideToMove) ? square<KING>(~sideToMove) : SQ_NONE;
// For unused piece types, the check squares are left uninitialized
si->nonSlidingRiders = 0;
for (PieceSet ps = piece_types(); ps;)
{
PieceType pt = pop_lsb(ps);
PieceType movePt = pt == KING ? king_type() : pt;
si->checkSquares[pt] = ksq != SQ_NONE ? attacks_bb(~sideToMove, movePt, ksq, pieces()) : Bitboard(0);
// Collect special piece types that require slower check and evasion detection
if (AttackRiderTypes[movePt] & NON_SLIDING_RIDERS)
si->nonSlidingRiders |= pieces(pt);
}
si->shak = si->checkersBB & (byTypeBB[KNIGHT] | byTypeBB[ROOK] | byTypeBB[BERS]);
si->bikjang = var->bikjangRule && ksq != SQ_NONE ? bool(attacks_bb(sideToMove, ROOK, ksq, pieces()) & pieces(sideToMove, KING)) : false;
si->chased = var->chasingRule ? chased() : Bitboard(0);
si->legalCapture = NO_VALUE;
if (var->extinctionPseudoRoyal)
{
si->pseudoRoyalCandidates = 0;
si->pseudoRoyals = 0;
for (PieceSet ps = extinction_piece_types(); ps;)
{
PieceType pt = pop_lsb(ps);
si->pseudoRoyalCandidates |= pieces(pt);
if (count(sideToMove, pt) <= var->extinctionPieceCount + 1)
si->pseudoRoyals |= pieces(sideToMove, pt);
if (count(~sideToMove, pt) <= var->extinctionPieceCount + 1)
si->pseudoRoyals |= pieces(~sideToMove, pt);
}
}
}
/// 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::set_state(StateInfo* si) const {
si->key = si->materialKey = 0;
si->pawnKey = Zobrist::noPawns;
si->nonPawnMaterial[WHITE] = si->nonPawnMaterial[BLACK] = VALUE_ZERO;
si->checkersBB = count<KING>(sideToMove) ? attackers_to(square<KING>(sideToMove), ~sideToMove) : Bitboard(0);
si->move = MOVE_NONE;
set_check_info(si);
for (Bitboard b = pieces(); b; )
{
Square s = pop_lsb(b);
Piece pc = piece_on(s);
si->key ^= Zobrist::psq[pc][s];
if (!pc)
si->key ^= Zobrist::wall[s];
else if (type_of(pc) == PAWN)
si->pawnKey ^= Zobrist::psq[pc][s];
else if (type_of(pc) != KING)
si->nonPawnMaterial[color_of(pc)] += PieceValue[MG][pc];
}
for (Bitboard b = si->epSquares; b; )
si->key ^= Zobrist::enpassant[file_of(pop_lsb(b))];
if (sideToMove == BLACK)
si->key ^= Zobrist::side;
si->key ^= Zobrist::castling[si->castlingRights];
for (Color c : {WHITE, BLACK})
for (PieceType pt = PAWN; pt <= KING; ++pt)
{
Piece pc = make_piece(c, pt);
for (int cnt = 0; cnt < pieceCount[pc]; ++cnt)
si->materialKey ^= Zobrist::psq[pc][cnt];
if (piece_drops() || seirawan_gating())
si->key ^= Zobrist::inHand[pc][pieceCountInHand[c][pt]];
}
if (check_counting())
for (Color c : {WHITE, BLACK})
si->key ^= Zobrist::checks[c][si->checksRemaining[c]];
}
/// 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.
Position& Position::set(const string& code, Color c, StateInfo* si) {
string sides[] = { code.substr(code.find('v') != string::npos ? code.find('v') + 1 : code.find('K', 1)), // Weak
code.substr(0, std::min(code.find('v'), code.find('K', 1))) }; // Strong
assert(sides[0].length() > 0 && sides[0].length() < 8);
assert(sides[1].length() > 0 && sides[1].length() < 8);
std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
string n = std::to_string(8);
string fenStr = sides[0] + "///////" + sides[1] + " w - - 0 10";
return set(variants.find("fairy")->second, fenStr, false, si, nullptr);
}
/// 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.
string Position::fen(bool sfen, bool showPromoted, int countStarted, std::string holdings, Bitboard fogArea) const {
int emptyCnt;
std::ostringstream ss;
for (Rank r = max_rank(); r >= RANK_1; --r)
{
for (File f = FILE_A; f <= max_file(); ++f)
{
for (emptyCnt = 0; f <= max_file() && !(pieces() & make_square(f, r)) && !(fogArea & make_square(f, r)); ++f)
++emptyCnt;
if (emptyCnt)
ss << emptyCnt;
if (f <= max_file())
{
if (empty(make_square(f, r)) || fogArea & make_square(f, r))
// Wall square
ss << "*";
else if (unpromoted_piece_on(make_square(f, r)))
// Promoted shogi pieces, e.g., +r for dragon
ss << "+" << piece_to_char()[unpromoted_piece_on(make_square(f, r))];
else
{
ss << piece_to_char()[piece_on(make_square(f, r))];
// Set promoted pieces
if (((captures_to_hand() && !drop_loop()) || two_boards() || showPromoted) && is_promoted(make_square(f, r)))
ss << "~";
}
}
}
if (r > RANK_1)
ss << '/';
}
// SFEN
if (sfen)
{
ss << (sideToMove == WHITE ? " b " : " w ");
for (Color c : {WHITE, BLACK})
for (PieceType pt = KING; pt >= PAWN; --pt)
if (pieceCountInHand[c][pt] > 0)
{
if (pieceCountInHand[c][pt] > 1)
ss << pieceCountInHand[c][pt];
ss << piece_to_char()[make_piece(c, pt)];
}
if (count_in_hand(ALL_PIECES) == 0)
ss << '-';
ss << " " << gamePly + 1;
return ss.str();
}
// pieces in hand
if (!variant()->freeDrops && (piece_drops() || seirawan_gating()))
{
ss << '[';
if (holdings != "-")
ss << holdings;
else
for (Color c : {WHITE, BLACK})
for (PieceType pt = KING; pt >= PAWN; --pt)
{
assert(pieceCountInHand[c][pt] >= 0);
ss << std::string(pieceCountInHand[c][pt], piece_to_char()[make_piece(c, pt)]);
}
ss << ']';
}
ss << (sideToMove == WHITE ? " w " : " b ");
// Disambiguation for chess960 "king" square
if (chess960 && can_castle(WHITE_CASTLING) && popcount(pieces(WHITE, castling_king_piece(WHITE)) & rank_bb(castling_rank(WHITE))) > 1)
ss << char('A' + castling_king_square(WHITE));
if (can_castle(WHITE_OO))
ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE_OO ))) : 'K');
if (can_castle(WHITE_OOO))
ss << (chess960 ? char('A' + file_of(castling_rook_square(WHITE_OOO))) : 'Q');
if (gating() && gates(WHITE) && (!seirawan_gating() || count_in_hand(WHITE, ALL_PIECES) > 0 || captures_to_hand()))
for (File f = FILE_A; f <= max_file(); ++f)
if ( (gates(WHITE) & file_bb(f))
// skip gating flags redundant with castling flags
&& !(!chess960 && can_castle(WHITE_CASTLING) && f == file_of(castling_king_square(WHITE)))
&& !(can_castle(WHITE_OO ) && f == file_of(castling_rook_square(WHITE_OO )))
&& !(can_castle(WHITE_OOO) && f == file_of(castling_rook_square(WHITE_OOO))))
ss << char('A' + f);
// Disambiguation for chess960 "king" square
if (chess960 && can_castle(BLACK_CASTLING) && popcount(pieces(BLACK, castling_king_piece(BLACK)) & rank_bb(castling_rank(BLACK))) > 1)
ss << char('a' + castling_king_square(BLACK));
if (can_castle(BLACK_OO))
ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK_OO ))) : 'k');
if (can_castle(BLACK_OOO))
ss << (chess960 ? char('a' + file_of(castling_rook_square(BLACK_OOO))) : 'q');
if (gating() && gates(BLACK) && (!seirawan_gating() || count_in_hand(BLACK, ALL_PIECES) > 0 || captures_to_hand()))
for (File f = FILE_A; f <= max_file(); ++f)
if ( (gates(BLACK) & file_bb(f))
// skip gating flags redundant with castling flags
&& !(!chess960 && can_castle(BLACK_CASTLING) && f == file_of(castling_king_square(BLACK)))
&& !(can_castle(BLACK_OO ) && f == file_of(castling_rook_square(BLACK_OO )))
&& !(can_castle(BLACK_OOO) && f == file_of(castling_rook_square(BLACK_OOO))))
ss << char('a' + f);
if (!can_castle(ANY_CASTLING) && !(gating() && (gates(WHITE) | gates(BLACK))))
ss << '-';
// Counting limit or ep-square
if (st->countingLimit)
ss << " " << counting_limit(countStarted) << " ";
else if (!ep_squares())
ss << " - ";
else
{
ss << " ";
for (Bitboard b = ep_squares(); b; )
ss << UCI::square(*this, pop_lsb(b));
ss << " ";
}
// Check count
if (check_counting())
ss << st->checksRemaining[WHITE] << "+" << st->checksRemaining[BLACK] << " ";
// Counting ply or 50-move rule counter
if (st->countingLimit)
ss << counting_ply(countStarted);
else
ss << st->rule50;
ss << " " << 1 + (gamePly - (sideToMove == BLACK)) / 2;
return ss.str();
}
/// 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.
Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners, Color c) const {
Bitboard blockers = 0;
pinners = 0;
if (s == SQ_NONE || !sliders)
return blockers;
// Snipers are sliders that attack 's' when a piece and other snipers are removed
Bitboard snipers = 0;
Bitboard slidingSnipers = 0;
if (var->fastAttacks)
{
snipers = ( (attacks_bb< ROOK>(s) & pieces(c, QUEEN, ROOK, CHANCELLOR))
| (attacks_bb<BISHOP>(s) & pieces(c, QUEEN, BISHOP, ARCHBISHOP))) & sliders;
slidingSnipers = snipers;
}
else
{
for (PieceSet ps = piece_types(); ps;)
{
PieceType pt = pop_lsb(ps);
Bitboard b = sliders & (PseudoAttacks[~c][pt][s] ^ LeaperAttacks[~c][pt][s]) & pieces(c, pt);
if (b)
{
// Consider asymmetrical moves (e.g., horse)
if (AttackRiderTypes[pt] & ASYMMETRICAL_RIDERS)
{
Bitboard asymmetricals = PseudoAttacks[~c][pt][s] & pieces(c, pt);
while (asymmetricals)
{
Square s2 = pop_lsb(asymmetricals);
if (!(attacks_from(c, pt, s2) & s))
snipers |= s2;
}
}
else
snipers |= b & ~attacks_bb(~c, pt, s, pieces());
if (AttackRiderTypes[pt] & ~HOPPING_RIDERS)
slidingSnipers |= snipers & pieces(pt);
}
}
// Diagonal rook pins in Janggi palace
if (diagonal_lines() & s)
{
Bitboard diags = diagonal_lines() & PseudoAttacks[~c][BISHOP][s] & sliders & pieces(c, ROOK);
while (diags)
{
Square s2 = pop_lsb(diags);
if (!(attacks_from(c, ROOK, s2) & s))
{
snipers |= s2;
slidingSnipers |= s2;
}
}
}
}
Bitboard occupancy = pieces() ^ slidingSnipers;
while (snipers)
{
Square sniperSq = pop_lsb(snipers);
bool isHopper = AttackRiderTypes[type_of(piece_on(sniperSq))] & HOPPING_RIDERS;
Bitboard b = between_bb(s, sniperSq, type_of(piece_on(sniperSq))) & (isHopper ? (pieces() ^ sniperSq) : occupancy);
if (b && (!more_than_one(b) || (isHopper && popcount(b) == 2)))
{
// Janggi cannons block each other
if ((pieces(JANGGI_CANNON) & sniperSq) && (pieces(JANGGI_CANNON) & b))
b &= pieces(JANGGI_CANNON);
blockers |= b;
if (b & pieces(color_of(piece_on(s))))
pinners |= sniperSq;
}
}
return blockers;
}
/// Position::attackers_to() computes a bitboard of all pieces which attack a
/// given square. Slider attacks use the occupied bitboard to indicate occupancy.
Bitboard Position::attackers_to(Square s, Bitboard occupied, Color c, Bitboard janggiCannons) const {
// Use a faster version for variants with moderate rule variations
if (var->fastAttacks)
{
return (pawn_attacks_bb(~c, s) & pieces(c, PAWN))
| (attacks_bb<KNIGHT>(s) & pieces(c, KNIGHT, ARCHBISHOP, CHANCELLOR))
| (attacks_bb< ROOK>(s, occupied) & pieces(c, ROOK, QUEEN, CHANCELLOR))
| (attacks_bb<BISHOP>(s, occupied) & pieces(c, BISHOP, QUEEN, ARCHBISHOP))
| (attacks_bb<KING>(s) & pieces(c, KING, COMMONER));
}
// Use a faster version for selected fairy pieces
if (var->fastAttacks2)
{
return (pawn_attacks_bb(~c, s) & pieces(c, PAWN, BREAKTHROUGH_PIECE, GOLD))
| (attacks_bb<KNIGHT>(s) & pieces(c, KNIGHT))
| (attacks_bb< ROOK>(s, occupied) & ( pieces(c, ROOK, QUEEN, DRAGON)
| (pieces(c, LANCE) & PseudoAttacks[~c][LANCE][s])))
| (attacks_bb<BISHOP>(s, occupied) & pieces(c, BISHOP, QUEEN, DRAGON_HORSE))
| (attacks_bb<KING>(s) & pieces(c, KING, COMMONER))
| (attacks_bb<FERS>(s) & pieces(c, FERS, DRAGON, SILVER))
| (attacks_bb<WAZIR>(s) & pieces(c, WAZIR, DRAGON_HORSE, GOLD))
| (LeaperAttacks[~c][SHOGI_KNIGHT][s] & pieces(c, SHOGI_KNIGHT))
| (LeaperAttacks[~c][SHOGI_PAWN][s] & pieces(c, SHOGI_PAWN, SILVER));
}
Bitboard b = 0;
for (PieceSet ps = piece_types(); ps;)
{
PieceType pt = pop_lsb(ps);
if (board_bb(c, pt) & s)
{
PieceType move_pt = pt == KING ? king_type() : pt;
// Consider asymmetrical moves (e.g., horse)
if (AttackRiderTypes[move_pt] & ASYMMETRICAL_RIDERS)
{
Bitboard asymmetricals = PseudoAttacks[~c][move_pt][s] & pieces(c, pt);
while (asymmetricals)
{
Square s2 = pop_lsb(asymmetricals);
if (attacks_bb(c, move_pt, s2, occupied) & s)
b |= s2;
}
}
else if (pt == JANGGI_CANNON)
b |= attacks_bb(~c, move_pt, s, occupied) & attacks_bb(~c, move_pt, s, occupied & ~janggiCannons) & pieces(c, JANGGI_CANNON);
else
b |= attacks_bb(~c, move_pt, s, occupied) & pieces(c, pt);
}
}
// Janggi palace moves
if (diagonal_lines() & s)
{
Bitboard diags = 0;
if (king_type() == WAZIR)
diags |= attacks_bb(~c, FERS, s, occupied) & pieces(c, KING);
diags |= attacks_bb(~c, FERS, s, occupied) & pieces(c, WAZIR);
diags |= attacks_bb(~c, PAWN, s, occupied) & pieces(c, SOLDIER);
diags |= rider_attacks_bb<RIDER_BISHOP>(s, occupied) & pieces(c, ROOK);
diags |= rider_attacks_bb<RIDER_CANNON_DIAG>(s, occupied)
& rider_attacks_bb<RIDER_CANNON_DIAG>(s, occupied & ~janggiCannons)
& pieces(c, JANGGI_CANNON);
b |= diags & diagonal_lines();
}
// Unpromoted soldiers
if (b & pieces(SOLDIER) && relative_rank(c, s, max_rank()) < var->soldierPromotionRank)
b ^= b & pieces(SOLDIER) & ~PseudoAttacks[~c][SHOGI_PAWN][s];
return b;
}