2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
38 #include "ucioption.h"
47 int Position::castleRightsMask[64];
49 Key Position::zobrist[2][8][64];
50 Key Position::zobEp[64];
51 Key Position::zobCastle[16];
52 Key Position::zobMaterial[2][8][16];
53 Key Position::zobSideToMove;
55 Value Position::MgPieceSquareTable[16][64];
56 Value Position::EgPieceSquareTable[16][64];
58 static bool RequestPending = false;
66 Position::Position(const Position& pos) {
70 Position::Position(const string& fen) {
75 /// Position::from_fen() initializes the position object with the given FEN
76 /// string. This function is not very robust - make sure that input FENs are
77 /// correct (this is assumed to be the responsibility of the GUI).
79 void Position::from_fen(const string& fen) {
81 static const string pieceLetters = "KQRBNPkqrbnp";
82 static const Piece pieces[] = { WK, WQ, WR, WB, WN, WP, BK, BQ, BR, BB, BN, BP };
90 for ( ; fen[i] != ' '; i++)
94 // Skip the given number of files
95 file += (fen[i] - '1' + 1);
98 else if (fen[i] == '/')
104 size_t idx = pieceLetters.find(fen[i]);
105 if (idx == string::npos)
107 std::cout << "Error in FEN at character " << i << std::endl;
110 Square square = make_square(file, rank);
111 put_piece(pieces[idx], square);
117 if (fen[i] != 'w' && fen[i] != 'b')
119 std::cout << "Error in FEN at character " << i << std::endl;
122 sideToMove = (fen[i] == 'w' ? WHITE : BLACK);
128 std::cout << "Error in FEN at character " << i << std::endl;
133 while(strchr("KQkqabcdefghABCDEFGH-", fen[i])) {
139 else if(fen[i] == 'K') allow_oo(WHITE);
140 else if(fen[i] == 'Q') allow_ooo(WHITE);
141 else if(fen[i] == 'k') allow_oo(BLACK);
142 else if(fen[i] == 'q') allow_ooo(BLACK);
143 else if(fen[i] >= 'A' && fen[i] <= 'H') {
144 File rookFile, kingFile = FILE_NONE;
145 for(Square square = SQ_B1; square <= SQ_G1; square++)
146 if(piece_on(square) == WK)
147 kingFile = square_file(square);
148 if(kingFile == FILE_NONE) {
149 std::cout << "Error in FEN at character " << i << std::endl;
152 initialKFile = kingFile;
153 rookFile = File(fen[i] - 'A') + FILE_A;
154 if(rookFile < initialKFile) {
156 initialQRFile = rookFile;
160 initialKRFile = rookFile;
163 else if(fen[i] >= 'a' && fen[i] <= 'h') {
164 File rookFile, kingFile = FILE_NONE;
165 for(Square square = SQ_B8; square <= SQ_G8; square++)
166 if(piece_on(square) == BK)
167 kingFile = square_file(square);
168 if(kingFile == FILE_NONE) {
169 std::cout << "Error in FEN at character " << i << std::endl;
172 initialKFile = kingFile;
173 rookFile = File(fen[i] - 'a') + FILE_A;
174 if(rookFile < initialKFile) {
176 initialQRFile = rookFile;
180 initialKRFile = rookFile;
184 std::cout << "Error in FEN at character " << i << std::endl;
191 while (fen[i] == ' ')
195 if ( i <= fen.length() - 2
196 && (fen[i] >= 'a' && fen[i] <= 'h')
197 && (fen[i+1] == '3' || fen[i+1] == '6'))
198 st->epSquare = square_from_string(fen.substr(i, 2));
200 // Various initialisation
201 for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
202 castleRightsMask[sq] = ALL_CASTLES;
204 castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO|WHITE_OOO);
205 castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO|BLACK_OOO);
206 castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO;
207 castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO;
208 castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO;
209 castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO;
213 st->key = compute_key();
214 st->pawnKey = compute_pawn_key();
215 st->materialKey = compute_material_key();
216 st->mgValue = compute_value<MidGame>();
217 st->egValue = compute_value<EndGame>();
218 st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
219 st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
223 /// Position::to_fen() converts the position object to a FEN string. This is
224 /// probably only useful for debugging.
226 const string Position::to_fen() const {
228 static const string pieceLetters = " PNBRQK pnbrqk";
232 for (Rank rank = RANK_8; rank >= RANK_1; rank--)
235 for (File file = FILE_A; file <= FILE_H; file++)
237 Square sq = make_square(file, rank);
238 if (!square_is_occupied(sq))
244 fen += (char)skip + '0';
247 fen += pieceLetters[piece_on(sq)];
250 fen += (char)skip + '0';
252 fen += (rank > RANK_1 ? '/' : ' ');
254 fen += (sideToMove == WHITE ? "w " : "b ");
255 if (st->castleRights != NO_CASTLES)
257 if (can_castle_kingside(WHITE)) fen += 'K';
258 if (can_castle_queenside(WHITE)) fen += 'Q';
259 if (can_castle_kingside(BLACK)) fen += 'k';
260 if (can_castle_queenside(BLACK)) fen += 'q';
265 if (ep_square() != SQ_NONE)
266 fen += square_to_string(ep_square());
274 /// Position::print() prints an ASCII representation of the position to
275 /// the standard output. If a move is given then also the san is print.
277 void Position::print(Move m) const {
279 static const string pieceLetters = " PNBRQK PNBRQK .";
281 // Check for reentrancy, as example when called from inside
282 // MovePicker that is used also here in move_to_san()
286 RequestPending = true;
288 std::cout << std::endl;
291 string col = (color_of_piece_on(move_from(m)) == BLACK ? ".." : "");
292 std::cout << "Move is: " << col << move_to_san(*this, m) << std::endl;
294 for (Rank rank = RANK_8; rank >= RANK_1; rank--)
296 std::cout << "+---+---+---+---+---+---+---+---+" << std::endl;
297 for (File file = FILE_A; file <= FILE_H; file++)
299 Square sq = make_square(file, rank);
300 Piece piece = piece_on(sq);
301 if (piece == EMPTY && square_color(sq) == WHITE)
304 char col = (color_of_piece_on(sq) == BLACK ? '=' : ' ');
305 std::cout << '|' << col << pieceLetters[piece] << col;
307 std::cout << '|' << std::endl;
309 std::cout << "+---+---+---+---+---+---+---+---+" << std::endl
310 << "Fen is: " << to_fen() << std::endl
311 << "Key is: " << st->key << std::endl;
313 RequestPending = false;
317 /// Position::copy() creates a copy of the input position.
319 void Position::copy(const Position& pos) {
321 memcpy(this, &pos, sizeof(Position));
322 saveState(); // detach and copy state info
326 /// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
327 /// king) pieces for the given color and for the given pinner type. Or, when
328 /// template parameter FindPinned is false, the pieces of the given color
329 /// candidate for a discovery check against the enemy king.
330 /// Note that checkersBB bitboard must be already updated.
332 template<bool FindPinned>
333 Bitboard Position::hidden_checkers(Color c) const {
335 Bitboard pinners, result = EmptyBoardBB;
337 // Pinned pieces protect our king, dicovery checks attack
339 Square ksq = king_square(FindPinned ? c : opposite_color(c));
341 // Pinners are sliders, not checkers, that give check when
342 // candidate pinned is removed.
343 pinners = (rooks_and_queens(FindPinned ? opposite_color(c) : c) & RookPseudoAttacks[ksq])
344 | (bishops_and_queens(FindPinned ? opposite_color(c) : c) & BishopPseudoAttacks[ksq]);
346 if (FindPinned && pinners)
347 pinners &= ~st->checkersBB;
351 Square s = pop_1st_bit(&pinners);
352 Bitboard b = squares_between(s, ksq) & occupied_squares();
356 if ( !(b & (b - 1)) // Only one bit set?
357 && (b & pieces_of_color(c))) // Is an our piece?
364 /// Position:pinned_pieces() returns a bitboard of all pinned (against the
365 /// king) pieces for the given color.
367 Bitboard Position::pinned_pieces(Color c) const {
369 return hidden_checkers<true>(c);
373 /// Position:discovered_check_candidates() returns a bitboard containing all
374 /// pieces for the given side which are candidates for giving a discovered
377 Bitboard Position::discovered_check_candidates(Color c) const {
379 return hidden_checkers<false>(c);
382 /// Position::attacks_to() computes a bitboard containing all pieces which
383 /// attacks a given square.
385 Bitboard Position::attacks_to(Square s) const {
387 return (pawn_attacks(BLACK, s) & pawns(WHITE))
388 | (pawn_attacks(WHITE, s) & pawns(BLACK))
389 | (piece_attacks<KNIGHT>(s) & pieces_of_type(KNIGHT))
390 | (piece_attacks<ROOK>(s) & rooks_and_queens())
391 | (piece_attacks<BISHOP>(s) & bishops_and_queens())
392 | (piece_attacks<KING>(s) & pieces_of_type(KING));
395 /// Position::piece_attacks_square() tests whether the piece on square f
396 /// attacks square t.
398 bool Position::piece_attacks_square(Piece p, Square f, Square t) const {
400 assert(square_is_ok(f));
401 assert(square_is_ok(t));
405 case WP: return pawn_attacks_square(WHITE, f, t);
406 case BP: return pawn_attacks_square(BLACK, f, t);
407 case WN: case BN: return piece_attacks_square<KNIGHT>(f, t);
408 case WB: case BB: return piece_attacks_square<BISHOP>(f, t);
409 case WR: case BR: return piece_attacks_square<ROOK>(f, t);
410 case WQ: case BQ: return piece_attacks_square<QUEEN>(f, t);
411 case WK: case BK: return piece_attacks_square<KING>(f, t);
418 /// Position::move_attacks_square() tests whether a move from the current
419 /// position attacks a given square.
421 bool Position::move_attacks_square(Move m, Square s) const {
423 assert(move_is_ok(m));
424 assert(square_is_ok(s));
426 Square f = move_from(m), t = move_to(m);
428 assert(square_is_occupied(f));
430 if (piece_attacks_square(piece_on(f), t, s))
433 // Move the piece and scan for X-ray attacks behind it
434 Bitboard occ = occupied_squares();
435 Color us = color_of_piece_on(f);
438 Bitboard xray = ( (rook_attacks_bb(s, occ) & rooks_and_queens())
439 |(bishop_attacks_bb(s, occ) & bishops_and_queens())) & pieces_of_color(us);
441 // If we have attacks we need to verify that are caused by our move
442 // and are not already existent ones.
443 return xray && (xray ^ (xray & piece_attacks<QUEEN>(s)));
447 /// Position::find_checkers() computes the checkersBB bitboard, which
448 /// contains a nonzero bit for each checking piece (0, 1 or 2). It
449 /// currently works by calling Position::attacks_to, which is probably
450 /// inefficient. Consider rewriting this function to use the last move
451 /// played, like in non-bitboard versions of Glaurung.
453 void Position::find_checkers() {
455 Color us = side_to_move();
456 st->checkersBB = attacks_to(king_square(us), opposite_color(us));
460 /// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
462 bool Position::pl_move_is_legal(Move m) const {
464 // If we're in check, all pseudo-legal moves are legal, because our
465 // check evasion generator only generates true legal moves.
466 return is_check() || pl_move_is_legal(m, pinned_pieces(side_to_move()));
469 bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
472 assert(move_is_ok(m));
473 assert(pinned == pinned_pieces(side_to_move()));
476 // Castling moves are checked for legality during move generation.
477 if (move_is_castle(m))
480 Color us = side_to_move();
481 Square from = move_from(m);
482 Square ksq = king_square(us);
484 assert(color_of_piece_on(from) == us);
485 assert(piece_on(ksq) == piece_of_color_and_type(us, KING));
487 // En passant captures are a tricky special case. Because they are
488 // rather uncommon, we do it simply by testing whether the king is attacked
489 // after the move is made
492 Color them = opposite_color(us);
493 Square to = move_to(m);
494 Square capsq = make_square(square_file(to), square_rank(from));
495 Bitboard b = occupied_squares();
497 assert(to == ep_square());
498 assert(piece_on(from) == piece_of_color_and_type(us, PAWN));
499 assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN));
500 assert(piece_on(to) == EMPTY);
503 clear_bit(&b, capsq);
506 return !(rook_attacks_bb(ksq, b) & rooks_and_queens(them))
507 && !(bishop_attacks_bb(ksq, b) & bishops_and_queens(them));
510 // If the moving piece is a king, check whether the destination
511 // square is attacked by the opponent.
513 return !(square_is_attacked(move_to(m), opposite_color(us)));
515 // A non-king move is legal if and only if it is not pinned or it
516 // is moving along the ray towards or away from the king.
518 || !bit_is_set(pinned, from)
519 || (direction_between_squares(from, ksq) == direction_between_squares(move_to(m), ksq)));
523 /// Position::move_is_check() tests whether a pseudo-legal move is a check
525 bool Position::move_is_check(Move m) const {
527 Bitboard dc = discovered_check_candidates(side_to_move());
528 return move_is_check(m, dc);
531 bool Position::move_is_check(Move m, Bitboard dcCandidates) const {
534 assert(move_is_ok(m));
535 assert(dcCandidates == discovered_check_candidates(side_to_move()));
537 Color us = side_to_move();
538 Color them = opposite_color(us);
539 Square from = move_from(m);
540 Square to = move_to(m);
541 Square ksq = king_square(them);
543 assert(color_of_piece_on(from) == us);
544 assert(piece_on(ksq) == piece_of_color_and_type(them, KING));
546 // Proceed according to the type of the moving piece
547 switch (type_of_piece_on(from))
551 if (bit_is_set(pawn_attacks(them, ksq), to)) // Normal check?
554 if ( dcCandidates // Discovered check?
555 && bit_is_set(dcCandidates, from)
556 && (direction_between_squares(from, ksq) != direction_between_squares(to, ksq)))
559 if (move_is_promotion(m)) // Promotion with check?
561 Bitboard b = occupied_squares();
564 switch (move_promotion_piece(m))
567 return bit_is_set(piece_attacks<KNIGHT>(to), ksq);
569 return bit_is_set(bishop_attacks_bb(to, b), ksq);
571 return bit_is_set(rook_attacks_bb(to, b), ksq);
573 return bit_is_set(queen_attacks_bb(to, b), ksq);
578 // En passant capture with check? We have already handled the case
579 // of direct checks and ordinary discovered check, the only case we
580 // need to handle is the unusual case of a discovered check through the
582 else if (move_is_ep(m))
584 Square capsq = make_square(square_file(to), square_rank(from));
585 Bitboard b = occupied_squares();
587 clear_bit(&b, capsq);
589 return (rook_attacks_bb(ksq, b) & rooks_and_queens(us))
590 ||(bishop_attacks_bb(ksq, b) & bishops_and_queens(us));
594 // Test discovered check and normal check according to piece type
596 return (dcCandidates && bit_is_set(dcCandidates, from))
597 || bit_is_set(piece_attacks<KNIGHT>(ksq), to);
600 return (dcCandidates && bit_is_set(dcCandidates, from))
601 || (direction_is_diagonal(ksq, to) && bit_is_set(piece_attacks<BISHOP>(ksq), to));
604 return (dcCandidates && bit_is_set(dcCandidates, from))
605 || (direction_is_straight(ksq, to) && bit_is_set(piece_attacks<ROOK>(ksq), to));
608 // Discovered checks are impossible!
609 assert(!bit_is_set(dcCandidates, from));
610 return ( (direction_is_straight(ksq, to) && bit_is_set(piece_attacks<ROOK>(ksq), to))
611 || (direction_is_diagonal(ksq, to) && bit_is_set(piece_attacks<BISHOP>(ksq), to)));
615 if ( bit_is_set(dcCandidates, from)
616 && (direction_between_squares(from, ksq) != direction_between_squares(to, ksq)))
619 // Castling with check?
620 if (move_is_castle(m))
622 Square kfrom, kto, rfrom, rto;
623 Bitboard b = occupied_squares();
629 kto = relative_square(us, SQ_G1);
630 rto = relative_square(us, SQ_F1);
632 kto = relative_square(us, SQ_C1);
633 rto = relative_square(us, SQ_D1);
635 clear_bit(&b, kfrom);
636 clear_bit(&b, rfrom);
639 return bit_is_set(rook_attacks_bb(rto, b), ksq);
643 default: // NO_PIECE_TYPE
651 /// Position::update_checkers() udpates chekers info given the move. It is called
652 /// in do_move() and is faster then find_checkers().
654 template<PieceType Piece>
655 inline void Position::update_checkers(Bitboard* pCheckersBB, Square ksq, Square from,
656 Square to, Bitboard dcCandidates) {
658 const bool Bishop = (Piece == QUEEN || Piece == BISHOP);
659 const bool Rook = (Piece == QUEEN || Piece == ROOK);
660 const bool Slider = Bishop || Rook;
663 if ( ( (Bishop && bit_is_set(BishopPseudoAttacks[ksq], to))
664 || (Rook && bit_is_set(RookPseudoAttacks[ksq], to)))
665 && bit_is_set(piece_attacks<Piece>(ksq), to)) // slow, try to early skip
666 set_bit(pCheckersBB, to);
668 else if ( Piece != KING
670 && bit_is_set(piece_attacks<Piece>(ksq), to))
671 set_bit(pCheckersBB, to);
674 if (Piece != QUEEN && bit_is_set(dcCandidates, from))
677 (*pCheckersBB) |= (piece_attacks<ROOK>(ksq) & rooks_and_queens(side_to_move()));
680 (*pCheckersBB) |= (piece_attacks<BISHOP>(ksq) & bishops_and_queens(side_to_move()));
685 /// Position::do_move() makes a move, and saves all information necessary
686 /// to a StateInfo object. The move is assumed to be legal.
687 /// Pseudo-legal moves should be filtered out before this function is called.
689 void Position::do_move(Move m, StateInfo& newSt) {
691 do_move(m, newSt, discovered_check_candidates(side_to_move()));
694 void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
697 assert(move_is_ok(m));
699 // Copy some fields of old state to our new StateInfo object except the
700 // ones which are recalculated from scratch anyway, then switch our state
701 // pointer to point to the new, ready to be updated, state.
702 struct ReducedStateInfo {
703 Key key, pawnKey, materialKey;
704 int castleRights, rule50;
706 Value mgValue, egValue;
710 memcpy(&newSt, st, sizeof(ReducedStateInfo));
711 newSt.capture = NO_PIECE_TYPE;
715 // Save the current key to the history[] array, in order to be able to
716 // detect repetition draws.
717 history[gamePly] = st->key;
719 // Increment the 50 moves rule draw counter. Resetting it to zero in the
720 // case of non-reversible moves is taken care of later.
723 // Update side to move
724 st->key ^= zobSideToMove;
726 if (move_is_castle(m))
730 Color us = side_to_move();
731 Color them = opposite_color(us);
732 Square from = move_from(m);
733 Square to = move_to(m);
734 bool ep = move_is_ep(m);
735 bool pm = move_is_promotion(m);
737 Piece piece = piece_on(from);
738 PieceType pt = type_of_piece(piece);
740 assert(color_of_piece_on(from) == us);
741 assert(color_of_piece_on(to) == them || square_is_empty(to));
742 assert(!(ep || pm) || piece == piece_of_color_and_type(us, PAWN));
743 assert(!pm || relative_rank(us, to) == RANK_8);
745 st->capture = type_of_piece_on(to);
747 if (st->capture || ep)
748 do_capture_move(st->capture, them, to, ep);
751 st->key ^= zobrist[us][pt][from] ^ zobrist[us][pt][to];
753 // Reset en passant square
754 if (st->epSquare != SQ_NONE)
756 st->key ^= zobEp[st->epSquare];
757 st->epSquare = SQ_NONE;
760 // Update castle rights, try to shortcut a common case
761 if ((castleRightsMask[from] & castleRightsMask[to]) != ALL_CASTLES)
763 st->key ^= zobCastle[st->castleRights];
764 st->castleRights &= castleRightsMask[from];
765 st->castleRights &= castleRightsMask[to];
766 st->key ^= zobCastle[st->castleRights];
769 // Prefetch TT access as soon as we know key is updated
770 TT.prefetch(st->key);
773 Bitboard move_bb = make_move_bb(from, to);
774 do_move_bb(&(byColorBB[us]), move_bb);
775 do_move_bb(&(byTypeBB[pt]), move_bb);
776 do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
778 board[to] = board[from];
781 // If the moving piece was a pawn do some special extra work
784 // Reset rule 50 draw counter
787 // Update pawn hash key
788 st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
790 // Set en passant square, only if moved pawn can be captured
791 if (abs(int(to) - int(from)) == 16)
793 if ( (us == WHITE && (pawn_attacks(WHITE, from + DELTA_N) & pawns(BLACK)))
794 || (us == BLACK && (pawn_attacks(BLACK, from + DELTA_S) & pawns(WHITE))))
796 st->epSquare = Square((int(from) + int(to)) / 2);
797 st->key ^= zobEp[st->epSquare];
802 // Update incremental scores
803 st->mgValue += pst_delta<MidGame>(piece, from, to);
804 st->egValue += pst_delta<EndGame>(piece, from, to);
806 // If the moving piece was a king, update the king square
810 // Update piece lists
811 pieceList[us][pt][index[from]] = to;
812 index[to] = index[from];
816 PieceType promotion = move_promotion_piece(m);
818 assert(promotion >= KNIGHT && promotion <= QUEEN);
820 // Insert promoted piece instead of pawn
821 clear_bit(&(byTypeBB[PAWN]), to);
822 set_bit(&(byTypeBB[promotion]), to);
823 board[to] = piece_of_color_and_type(us, promotion);
825 // Partially revert hash keys update
826 st->key ^= zobrist[us][PAWN][to] ^ zobrist[us][promotion][to];
827 st->pawnKey ^= zobrist[us][PAWN][to];
829 // Update material key
830 st->materialKey ^= zobMaterial[us][PAWN][pieceCount[us][PAWN]];
831 st->materialKey ^= zobMaterial[us][promotion][pieceCount[us][promotion]+1];
833 // Update piece counts
834 pieceCount[us][PAWN]--;
835 pieceCount[us][promotion]++;
837 // Update piece lists
838 pieceList[us][PAWN][index[from]] = pieceList[us][PAWN][pieceCount[us][PAWN]];
839 index[pieceList[us][PAWN][index[from]]] = index[from];
840 pieceList[us][promotion][pieceCount[us][promotion] - 1] = to;
841 index[to] = pieceCount[us][promotion] - 1;
843 // Partially revert and update incremental scores
844 st->mgValue -= pst<MidGame>(us, PAWN, to);
845 st->mgValue += pst<MidGame>(us, promotion, to);
846 st->egValue -= pst<EndGame>(us, PAWN, to);
847 st->egValue += pst<EndGame>(us, promotion, to);
850 st->npMaterial[us] += piece_value_midgame(promotion);
853 // Update checkers bitboard, piece must be already moved
855 st->checkersBB = attacks_to(king_square(them), us);
858 st->checkersBB = EmptyBoardBB; // FIXME EP ?
859 Square ksq = king_square(them);
862 case PAWN: update_checkers<PAWN>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
863 case KNIGHT: update_checkers<KNIGHT>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
864 case BISHOP: update_checkers<BISHOP>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
865 case ROOK: update_checkers<ROOK>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
866 case QUEEN: update_checkers<QUEEN>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
867 case KING: update_checkers<KING>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
868 default: assert(false); break;
874 sideToMove = opposite_color(sideToMove);
877 st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
878 st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
884 /// Position::do_capture_move() is a private method used to update captured
885 /// piece info. It is called from the main Position::do_move function.
887 void Position::do_capture_move(PieceType capture, Color them, Square to, bool ep) {
889 assert(capture != KING);
896 capsq = (them == BLACK)? (to - DELTA_N) : (to - DELTA_S);
898 assert(to == st->epSquare);
899 assert(relative_rank(opposite_color(them), to) == RANK_6);
900 assert(piece_on(to) == EMPTY);
901 //assert(piece_on(from) == piece_of_color_and_type(us, PAWN));
902 assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN));
904 board[capsq] = EMPTY;
907 // Remove captured piece
908 clear_bit(&(byColorBB[them]), capsq);
909 clear_bit(&(byTypeBB[capture]), capsq);
910 clear_bit(&(byTypeBB[0]), capsq); // HACK: byTypeBB[0] == occupied squares
913 st->key ^= zobrist[them][capture][capsq];
915 // If the captured piece was a pawn, update pawn hash key
917 st->pawnKey ^= zobrist[them][PAWN][capsq];
919 // Update incremental scores
920 st->mgValue -= pst<MidGame>(them, capture, capsq);
921 st->egValue -= pst<EndGame>(them, capture, capsq);
925 st->npMaterial[them] -= piece_value_midgame(capture);
927 // Update material hash key
928 st->materialKey ^= zobMaterial[them][capture][pieceCount[them][capture]];
930 // Update piece count
931 pieceCount[them][capture]--;
934 pieceList[them][capture][index[capsq]] = pieceList[them][capture][pieceCount[them][capture]];
935 index[pieceList[them][capture][index[capsq]]] = index[capsq];
937 // Reset rule 50 counter
942 /// Position::do_castle_move() is a private method used to make a castling
943 /// move. It is called from the main Position::do_move function. Note that
944 /// castling moves are encoded as "king captures friendly rook" moves, for
945 /// instance white short castling in a non-Chess960 game is encoded as e1h1.
947 void Position::do_castle_move(Move m) {
950 assert(move_is_ok(m));
951 assert(move_is_castle(m));
953 Color us = side_to_move();
954 Color them = opposite_color(us);
956 // Find source squares for king and rook
957 Square kfrom = move_from(m);
958 Square rfrom = move_to(m); // HACK: See comment at beginning of function
961 assert(piece_on(kfrom) == piece_of_color_and_type(us, KING));
962 assert(piece_on(rfrom) == piece_of_color_and_type(us, ROOK));
964 // Find destination squares for king and rook
965 if (rfrom > kfrom) // O-O
967 kto = relative_square(us, SQ_G1);
968 rto = relative_square(us, SQ_F1);
970 kto = relative_square(us, SQ_C1);
971 rto = relative_square(us, SQ_D1);
975 Bitboard kmove_bb = make_move_bb(kfrom, kto);
976 do_move_bb(&(byColorBB[us]), kmove_bb);
977 do_move_bb(&(byTypeBB[KING]), kmove_bb);
978 do_move_bb(&(byTypeBB[0]), kmove_bb); // HACK: byTypeBB[0] == occupied squares
980 Bitboard rmove_bb = make_move_bb(rfrom, rto);
981 do_move_bb(&(byColorBB[us]), rmove_bb);
982 do_move_bb(&(byTypeBB[ROOK]), rmove_bb);
983 do_move_bb(&(byTypeBB[0]), rmove_bb); // HACK: byTypeBB[0] == occupied squares
985 // Update board array
986 Piece king = piece_of_color_and_type(us, KING);
987 Piece rook = piece_of_color_and_type(us, ROOK);
988 board[kfrom] = board[rfrom] = EMPTY;
992 // Update king square
993 kingSquare[us] = kto;
995 // Update piece lists
996 pieceList[us][KING][index[kfrom]] = kto;
997 pieceList[us][ROOK][index[rfrom]] = rto;
998 int tmp = index[rfrom];
999 index[kto] = index[kfrom];
1002 // Update incremental scores
1003 st->mgValue += pst_delta<MidGame>(king, kfrom, kto);
1004 st->egValue += pst_delta<EndGame>(king, kfrom, kto);
1005 st->mgValue += pst_delta<MidGame>(rook, rfrom, rto);
1006 st->egValue += pst_delta<EndGame>(rook, rfrom, rto);
1009 st->key ^= zobrist[us][KING][kfrom] ^ zobrist[us][KING][kto];
1010 st->key ^= zobrist[us][ROOK][rfrom] ^ zobrist[us][ROOK][rto];
1012 // Clear en passant square
1013 if (st->epSquare != SQ_NONE)
1015 st->key ^= zobEp[st->epSquare];
1016 st->epSquare = SQ_NONE;
1019 // Update castling rights
1020 st->key ^= zobCastle[st->castleRights];
1021 st->castleRights &= castleRightsMask[kfrom];
1022 st->key ^= zobCastle[st->castleRights];
1024 // Reset rule 50 counter
1027 // Update checkers BB
1028 st->checkersBB = attacks_to(king_square(them), us);
1032 /// Position::undo_move() unmakes a move. When it returns, the position should
1033 /// be restored to exactly the same state as before the move was made.
1035 void Position::undo_move(Move m) {
1038 assert(move_is_ok(m));
1041 sideToMove = opposite_color(sideToMove);
1043 if (move_is_castle(m))
1044 undo_castle_move(m);
1045 else if (move_is_ep(m))
1049 Color us = side_to_move();
1050 Color them = opposite_color(us);
1051 Square from = move_from(m);
1052 Square to = move_to(m);
1053 bool pm = move_is_promotion(m);
1055 PieceType piece = type_of_piece_on(to);
1057 assert(square_is_empty(from));
1058 assert(color_of_piece_on(to) == us);
1059 assert(!pm || relative_rank(us, to) == RANK_8);
1063 PieceType promotion = move_promotion_piece(m);
1065 assert(piece_on(to) == piece_of_color_and_type(us, promotion));
1066 assert(promotion >= KNIGHT && promotion <= QUEEN);
1068 // Replace promoted piece with a pawn
1069 clear_bit(&(byTypeBB[promotion]), to);
1070 set_bit(&(byTypeBB[PAWN]), to);
1072 // Update piece list replacing promotion piece with a pawn
1073 pieceList[us][promotion][index[to]] = pieceList[us][promotion][pieceCount[us][promotion] - 1];
1074 index[pieceList[us][promotion][index[to]]] = index[to];
1075 pieceList[us][PAWN][pieceCount[us][PAWN]] = to;
1076 index[to] = pieceCount[us][PAWN];
1078 // Update piece counts
1079 pieceCount[us][promotion]--;
1080 pieceCount[us][PAWN]++;
1085 // Put the piece back at the source square
1086 Bitboard move_bb = make_move_bb(to, from);
1087 do_move_bb(&(byColorBB[us]), move_bb);
1088 do_move_bb(&(byTypeBB[piece]), move_bb);
1089 do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
1090 board[from] = piece_of_color_and_type(us, piece);
1092 // If the moving piece was a king, update the king square
1094 kingSquare[us] = from;
1096 // Update piece list
1097 pieceList[us][piece][index[to]] = from;
1098 index[from] = index[to];
1102 assert(st->capture != KING);
1104 // Restore the captured piece
1105 set_bit(&(byColorBB[them]), to);
1106 set_bit(&(byTypeBB[st->capture]), to);
1107 set_bit(&(byTypeBB[0]), to);
1108 board[to] = piece_of_color_and_type(them, st->capture);
1110 // Update piece list
1111 pieceList[them][st->capture][pieceCount[them][st->capture]] = to;
1112 index[to] = pieceCount[them][st->capture];
1114 // Update piece count
1115 pieceCount[them][st->capture]++;
1120 // Finally point our state pointer back to the previous state
1127 /// Position::undo_castle_move() is a private method used to unmake a castling
1128 /// move. It is called from the main Position::undo_move function. Note that
1129 /// castling moves are encoded as "king captures friendly rook" moves, for
1130 /// instance white short castling in a non-Chess960 game is encoded as e1h1.
1132 void Position::undo_castle_move(Move m) {
1134 assert(move_is_ok(m));
1135 assert(move_is_castle(m));
1137 // When we have arrived here, some work has already been done by
1138 // Position::undo_move. In particular, the side to move has been switched,
1139 // so the code below is correct.
1140 Color us = side_to_move();
1142 // Find source squares for king and rook
1143 Square kfrom = move_from(m);
1144 Square rfrom = move_to(m); // HACK: See comment at beginning of function
1147 // Find destination squares for king and rook
1148 if (rfrom > kfrom) // O-O
1150 kto = relative_square(us, SQ_G1);
1151 rto = relative_square(us, SQ_F1);
1153 kto = relative_square(us, SQ_C1);
1154 rto = relative_square(us, SQ_D1);
1157 assert(piece_on(kto) == piece_of_color_and_type(us, KING));
1158 assert(piece_on(rto) == piece_of_color_and_type(us, ROOK));
1160 // Put the pieces back at the source square
1161 Bitboard kmove_bb = make_move_bb(kto, kfrom);
1162 do_move_bb(&(byColorBB[us]), kmove_bb);
1163 do_move_bb(&(byTypeBB[KING]), kmove_bb);
1164 do_move_bb(&(byTypeBB[0]), kmove_bb); // HACK: byTypeBB[0] == occupied squares
1166 Bitboard rmove_bb = make_move_bb(rto, rfrom);
1167 do_move_bb(&(byColorBB[us]), rmove_bb);
1168 do_move_bb(&(byTypeBB[ROOK]), rmove_bb);
1169 do_move_bb(&(byTypeBB[0]), rmove_bb); // HACK: byTypeBB[0] == occupied squares
1172 board[rto] = board[kto] = EMPTY;
1173 board[rfrom] = piece_of_color_and_type(us, ROOK);
1174 board[kfrom] = piece_of_color_and_type(us, KING);
1176 // Update king square
1177 kingSquare[us] = kfrom;
1179 // Update piece lists
1180 pieceList[us][KING][index[kto]] = kfrom;
1181 pieceList[us][ROOK][index[rto]] = rfrom;
1182 int tmp = index[rto]; // Necessary because we may have rto == kfrom in FRC.
1183 index[kfrom] = index[kto];
1188 /// Position::undo_ep_move() is a private method used to unmake an en passant
1189 /// capture. It is called from the main Position::undo_move function.
1191 void Position::undo_ep_move(Move m) {
1193 assert(move_is_ok(m));
1194 assert(move_is_ep(m));
1196 // When we have arrived here, some work has already been done by
1197 // Position::undo_move. In particular, the side to move has been switched,
1198 // so the code below is correct.
1199 Color us = side_to_move();
1200 Color them = opposite_color(us);
1201 Square from = move_from(m);
1202 Square to = move_to(m);
1203 Square capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
1205 assert(to == st->previous->epSquare);
1206 assert(relative_rank(us, to) == RANK_6);
1207 assert(piece_on(to) == piece_of_color_and_type(us, PAWN));
1208 assert(piece_on(from) == EMPTY);
1209 assert(piece_on(capsq) == EMPTY);
1211 // Restore captured pawn
1212 set_bit(&(byColorBB[them]), capsq);
1213 set_bit(&(byTypeBB[PAWN]), capsq);
1214 set_bit(&(byTypeBB[0]), capsq);
1215 board[capsq] = piece_of_color_and_type(them, PAWN);
1217 // Move capturing pawn back to source square
1218 Bitboard move_bb = make_move_bb(to, from);
1219 do_move_bb(&(byColorBB[us]), move_bb);
1220 do_move_bb(&(byTypeBB[PAWN]), move_bb);
1221 do_move_bb(&(byTypeBB[0]), move_bb);
1223 board[from] = piece_of_color_and_type(us, PAWN);
1225 // Update piece list
1226 pieceList[us][PAWN][index[to]] = from;
1227 index[from] = index[to];
1228 pieceList[them][PAWN][pieceCount[them][PAWN]] = capsq;
1229 index[capsq] = pieceCount[them][PAWN];
1231 // Update piece count
1232 pieceCount[them][PAWN]++;
1236 /// Position::do_null_move makes() a "null move": It switches the side to move
1237 /// and updates the hash key without executing any move on the board.
1239 void Position::do_null_move(StateInfo& backupSt) {
1242 assert(!is_check());
1244 // Back up the information necessary to undo the null move to the supplied
1245 // StateInfo object.
1246 // Note that differently from normal case here backupSt is actually used as
1247 // a backup storage not as a new state to be used.
1248 backupSt.epSquare = st->epSquare;
1249 backupSt.key = st->key;
1250 backupSt.mgValue = st->mgValue;
1251 backupSt.egValue = st->egValue;
1252 backupSt.previous = st->previous;
1253 st->previous = &backupSt;
1255 // Save the current key to the history[] array, in order to be able to
1256 // detect repetition draws.
1257 history[gamePly] = st->key;
1259 // Update the necessary information
1260 if (st->epSquare != SQ_NONE)
1261 st->key ^= zobEp[st->epSquare];
1263 st->key ^= zobSideToMove;
1264 TT.prefetch(st->key);
1265 sideToMove = opposite_color(sideToMove);
1266 st->epSquare = SQ_NONE;
1270 st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
1271 st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
1277 /// Position::undo_null_move() unmakes a "null move".
1279 void Position::undo_null_move() {
1282 assert(!is_check());
1284 // Restore information from the our backup StateInfo object
1285 st->epSquare = st->previous->epSquare;
1286 st->key = st->previous->key;
1287 st->mgValue = st->previous->mgValue;
1288 st->egValue = st->previous->egValue;
1289 st->previous = st->previous->previous;
1291 // Update the necessary information
1292 sideToMove = opposite_color(sideToMove);
1300 /// Position::see() is a static exchange evaluator: It tries to estimate the
1301 /// material gain or loss resulting from a move. There are three versions of
1302 /// this function: One which takes a destination square as input, one takes a
1303 /// move, and one which takes a 'from' and a 'to' square. The function does
1304 /// not yet understand promotions captures.
1306 int Position::see(Square to) const {
1308 assert(square_is_ok(to));
1309 return see(SQ_NONE, to);
1312 int Position::see(Move m) const {
1314 assert(move_is_ok(m));
1315 return see(move_from(m), move_to(m));
1318 int Position::see_sign(Move m) const {
1320 assert(move_is_ok(m));
1322 Square from = move_from(m);
1323 Square to = move_to(m);
1325 // Early return if SEE cannot be negative because capturing piece value
1326 // is not bigger then captured one.
1327 if ( midgame_value_of_piece_on(from) <= midgame_value_of_piece_on(to)
1328 && type_of_piece_on(from) != KING)
1331 return see(from, to);
1334 int Position::see(Square from, Square to) const {
1337 static const int seeValues[18] = {
1338 0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
1339 RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0,
1340 0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
1341 RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0,
1345 Bitboard attackers, stmAttackers, occ, b;
1347 assert(square_is_ok(from) || from == SQ_NONE);
1348 assert(square_is_ok(to));
1350 // Initialize colors
1351 Color us = (from != SQ_NONE ? color_of_piece_on(from) : opposite_color(color_of_piece_on(to)));
1352 Color them = opposite_color(us);
1354 // Initialize pieces
1355 Piece piece = piece_on(from);
1356 Piece capture = piece_on(to);
1358 // Find all attackers to the destination square, with the moving piece
1359 // removed, but possibly an X-ray attacker added behind it.
1360 occ = occupied_squares();
1362 // Handle en passant moves
1363 if (st->epSquare == to && type_of_piece_on(from) == PAWN)
1365 assert(capture == EMPTY);
1367 Square capQq = (side_to_move() == WHITE)? (to - DELTA_N) : (to - DELTA_S);
1368 capture = piece_on(capQq);
1369 assert(type_of_piece_on(capQq) == PAWN);
1371 // Remove the captured pawn
1372 clear_bit(&occ, capQq);
1377 clear_bit(&occ, from);
1378 attackers = (rook_attacks_bb(to, occ) & rooks_and_queens())
1379 | (bishop_attacks_bb(to, occ) & bishops_and_queens())
1380 | (piece_attacks<KNIGHT>(to) & knights())
1381 | (piece_attacks<KING>(to) & kings())
1382 | (pawn_attacks(WHITE, to) & pawns(BLACK))
1383 | (pawn_attacks(BLACK, to) & pawns(WHITE));
1385 if (from != SQ_NONE)
1388 // If we don't have any attacker we are finished
1389 if ((attackers & pieces_of_color(us)) == EmptyBoardBB)
1392 // Locate the least valuable attacker to the destination square
1393 // and use it to initialize from square.
1395 for (pt = PAWN; !(attackers & pieces_of_color_and_type(us, pt)); pt++)
1398 from = first_1(attackers & pieces_of_color_and_type(us, pt));
1399 piece = piece_on(from);
1402 // If the opponent has no attackers we are finished
1403 stmAttackers = attackers & pieces_of_color(them);
1405 return seeValues[capture];
1407 attackers &= occ; // Remove the moving piece
1409 // The destination square is defended, which makes things rather more
1410 // difficult to compute. We proceed by building up a "swap list" containing
1411 // the material gain or loss at each stop in a sequence of captures to the
1412 // destination square, where the sides alternately capture, and always
1413 // capture with the least valuable piece. After each capture, we look for
1414 // new X-ray attacks from behind the capturing piece.
1415 int lastCapturingPieceValue = seeValues[piece];
1416 int swapList[32], n = 1;
1420 swapList[0] = seeValues[capture];
1423 // Locate the least valuable attacker for the side to move. The loop
1424 // below looks like it is potentially infinite, but it isn't. We know
1425 // that the side to move still has at least one attacker left.
1426 for (pt = PAWN; !(stmAttackers & pieces_of_type(pt)); pt++)
1429 // Remove the attacker we just found from the 'attackers' bitboard,
1430 // and scan for new X-ray attacks behind the attacker.
1431 b = stmAttackers & pieces_of_type(pt);
1432 occ ^= (b & (~b + 1));
1433 attackers |= (rook_attacks_bb(to, occ) & rooks_and_queens())
1434 | (bishop_attacks_bb(to, occ) & bishops_and_queens());
1438 // Add the new entry to the swap list
1440 swapList[n] = -swapList[n - 1] + lastCapturingPieceValue;
1443 // Remember the value of the capturing piece, and change the side to move
1444 // before beginning the next iteration
1445 lastCapturingPieceValue = seeValues[pt];
1446 c = opposite_color(c);
1447 stmAttackers = attackers & pieces_of_color(c);
1449 // Stop after a king capture
1450 if (pt == KING && stmAttackers)
1453 swapList[n++] = QueenValueMidgame*10;
1456 } while (stmAttackers);
1458 // Having built the swap list, we negamax through it to find the best
1459 // achievable score from the point of view of the side to move
1461 swapList[n-1] = Min(-swapList[n], swapList[n-1]);
1467 /// Position::saveState() copies the content of the current state
1468 /// inside startState and makes st point to it. This is needed
1469 /// when the st pointee could become stale, as example because
1470 /// the caller is about to going out of scope.
1472 void Position::saveState() {
1476 st->previous = NULL; // as a safe guard
1480 /// Position::clear() erases the position object to a pristine state, with an
1481 /// empty board, white to move, and no castling rights.
1483 void Position::clear() {
1486 memset(st, 0, sizeof(StateInfo));
1487 st->epSquare = SQ_NONE;
1489 memset(index, 0, sizeof(int) * 64);
1490 memset(byColorBB, 0, sizeof(Bitboard) * 2);
1492 for (int i = 0; i < 64; i++)
1495 for (int i = 0; i < 7; i++)
1497 byTypeBB[i] = EmptyBoardBB;
1498 pieceCount[0][i] = pieceCount[1][i] = 0;
1499 for (int j = 0; j < 8; j++)
1500 pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
1505 initialKFile = FILE_E;
1506 initialKRFile = FILE_H;
1507 initialQRFile = FILE_A;
1511 /// Position::reset_game_ply() simply sets gamePly to 0. It is used from the
1512 /// UCI interface code, whenever a non-reversible move is made in a
1513 /// 'position fen <fen> moves m1 m2 ...' command. This makes it possible
1514 /// for the program to handle games of arbitrary length, as long as the GUI
1515 /// handles draws by the 50 move rule correctly.
1517 void Position::reset_game_ply() {
1523 /// Position::put_piece() puts a piece on the given square of the board,
1524 /// updating the board array, bitboards, and piece counts.
1526 void Position::put_piece(Piece p, Square s) {
1528 Color c = color_of_piece(p);
1529 PieceType pt = type_of_piece(p);
1532 index[s] = pieceCount[c][pt];
1533 pieceList[c][pt][index[s]] = s;
1535 set_bit(&(byTypeBB[pt]), s);
1536 set_bit(&(byColorBB[c]), s);
1537 set_bit(&byTypeBB[0], s); // HACK: byTypeBB[0] contains all occupied squares.
1539 pieceCount[c][pt]++;
1546 /// Position::allow_oo() gives the given side the right to castle kingside.
1547 /// Used when setting castling rights during parsing of FEN strings.
1549 void Position::allow_oo(Color c) {
1551 st->castleRights |= (1 + int(c));
1555 /// Position::allow_ooo() gives the given side the right to castle queenside.
1556 /// Used when setting castling rights during parsing of FEN strings.
1558 void Position::allow_ooo(Color c) {
1560 st->castleRights |= (4 + 4*int(c));
1564 /// Position::compute_key() computes the hash key of the position. The hash
1565 /// key is usually updated incrementally as moves are made and unmade, the
1566 /// compute_key() function is only used when a new position is set up, and
1567 /// to verify the correctness of the hash key when running in debug mode.
1569 Key Position::compute_key() const {
1571 Key result = Key(0ULL);
1573 for (Square s = SQ_A1; s <= SQ_H8; s++)
1574 if (square_is_occupied(s))
1575 result ^= zobrist[color_of_piece_on(s)][type_of_piece_on(s)][s];
1577 if (ep_square() != SQ_NONE)
1578 result ^= zobEp[ep_square()];
1580 result ^= zobCastle[st->castleRights];
1581 if (side_to_move() == BLACK)
1582 result ^= zobSideToMove;
1588 /// Position::compute_pawn_key() computes the hash key of the position. The
1589 /// hash key is usually updated incrementally as moves are made and unmade,
1590 /// the compute_pawn_key() function is only used when a new position is set
1591 /// up, and to verify the correctness of the pawn hash key when running in
1594 Key Position::compute_pawn_key() const {
1596 Key result = Key(0ULL);
1600 for (Color c = WHITE; c <= BLACK; c++)
1605 s = pop_1st_bit(&b);
1606 result ^= zobrist[c][PAWN][s];
1613 /// Position::compute_material_key() computes the hash key of the position.
1614 /// The hash key is usually updated incrementally as moves are made and unmade,
1615 /// the compute_material_key() function is only used when a new position is set
1616 /// up, and to verify the correctness of the material hash key when running in
1619 Key Position::compute_material_key() const {
1621 Key result = Key(0ULL);
1622 for (Color c = WHITE; c <= BLACK; c++)
1623 for (PieceType pt = PAWN; pt <= QUEEN; pt++)
1625 int count = piece_count(c, pt);
1626 for (int i = 0; i <= count; i++)
1627 result ^= zobMaterial[c][pt][i];
1633 /// Position::compute_value() compute the incremental scores for the middle
1634 /// game and the endgame. These functions are used to initialize the incremental
1635 /// scores when a new position is set up, and to verify that the scores are correctly
1636 /// updated by do_move and undo_move when the program is running in debug mode.
1637 template<Position::GamePhase Phase>
1638 Value Position::compute_value() const {
1640 Value result = Value(0);
1644 for (Color c = WHITE; c <= BLACK; c++)
1645 for (PieceType pt = PAWN; pt <= KING; pt++)
1647 b = pieces_of_color_and_type(c, pt);
1650 s = pop_1st_bit(&b);
1651 assert(piece_on(s) == piece_of_color_and_type(c, pt));
1652 result += pst<Phase>(c, pt, s);
1656 const Value TempoValue = (Phase == MidGame ? TempoValueMidgame : TempoValueEndgame);
1657 result += (side_to_move() == WHITE)? TempoValue / 2 : -TempoValue / 2;
1662 /// Position::compute_non_pawn_material() computes the total non-pawn middle
1663 /// game material score for the given side. Material scores are updated
1664 /// incrementally during the search, this function is only used while
1665 /// initializing a new Position object.
1667 Value Position::compute_non_pawn_material(Color c) const {
1669 Value result = Value(0);
1671 for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
1673 Bitboard b = pieces_of_color_and_type(c, pt);
1676 assert(piece_on(first_1(b)) == piece_of_color_and_type(c, pt));
1678 result += piece_value_midgame(pt);
1685 /// Position::is_draw() tests whether the position is drawn by material,
1686 /// repetition, or the 50 moves rule. It does not detect stalemates, this
1687 /// must be done by the search.
1689 bool Position::is_draw() const {
1691 // Draw by material?
1693 && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMidgame))
1696 // Draw by the 50 moves rule?
1697 if (st->rule50 > 100 || (st->rule50 == 100 && !is_check()))
1700 // Draw by repetition?
1701 for (int i = 2; i < Min(gamePly, st->rule50); i += 2)
1702 if (history[gamePly - i] == st->key)
1709 /// Position::is_mate() returns true or false depending on whether the
1710 /// side to move is checkmated.
1712 bool Position::is_mate() const {
1714 MoveStack moves[256];
1716 return is_check() && !generate_evasions(*this, moves, pinned_pieces(sideToMove));
1720 /// Position::has_mate_threat() tests whether a given color has a mate in one
1721 /// from the current position.
1723 bool Position::has_mate_threat(Color c) {
1726 Color stm = side_to_move();
1731 // If the input color is not equal to the side to move, do a null move
1735 MoveStack mlist[120];
1737 bool result = false;
1738 Bitboard dc = discovered_check_candidates(sideToMove);
1739 Bitboard pinned = pinned_pieces(sideToMove);
1741 // Generate pseudo-legal non-capture and capture check moves
1742 count = generate_non_capture_checks(*this, mlist, dc);
1743 count += generate_captures(*this, mlist + count);
1745 // Loop through the moves, and see if one of them is mate
1746 for (int i = 0; i < count; i++)
1748 Move move = mlist[i].move;
1750 if (!pl_move_is_legal(move, pinned))
1760 // Undo null move, if necessary
1768 /// Position::init_zobrist() is a static member function which initializes the
1769 /// various arrays used to compute hash keys.
1771 void Position::init_zobrist() {
1773 for (int i = 0; i < 2; i++)
1774 for (int j = 0; j < 8; j++)
1775 for (int k = 0; k < 64; k++)
1776 zobrist[i][j][k] = Key(genrand_int64());
1778 for (int i = 0; i < 64; i++)
1779 zobEp[i] = Key(genrand_int64());
1781 for (int i = 0; i < 16; i++)
1782 zobCastle[i] = genrand_int64();
1784 zobSideToMove = genrand_int64();
1786 for (int i = 0; i < 2; i++)
1787 for (int j = 0; j < 8; j++)
1788 for (int k = 0; k < 16; k++)
1789 zobMaterial[i][j][k] = (k > 0)? Key(genrand_int64()) : Key(0LL);
1791 for (int i = 0; i < 16; i++)
1792 zobMaterial[0][KING][i] = zobMaterial[1][KING][i] = Key(0ULL);
1796 /// Position::init_piece_square_tables() initializes the piece square tables.
1797 /// This is a two-step operation: First, the white halves of the tables are
1798 /// copied from the MgPST[][] and EgPST[][] arrays, with a small random number
1799 /// added to each entry if the "Randomness" UCI parameter is non-zero.
1800 /// Second, the black halves of the tables are initialized by mirroring
1801 /// and changing the sign of the corresponding white scores.
1803 void Position::init_piece_square_tables() {
1805 int r = get_option_value_int("Randomness"), i;
1806 for (Square s = SQ_A1; s <= SQ_H8; s++)
1807 for (Piece p = WP; p <= WK; p++)
1809 i = (r == 0)? 0 : (genrand_int32() % (r*2) - r);
1810 MgPieceSquareTable[p][s] = Value(MgPST[p][s] + i);
1811 EgPieceSquareTable[p][s] = Value(EgPST[p][s] + i);
1814 for (Square s = SQ_A1; s <= SQ_H8; s++)
1815 for (Piece p = BP; p <= BK; p++)
1817 MgPieceSquareTable[p][s] = -MgPieceSquareTable[p-8][flip_square(s)];
1818 EgPieceSquareTable[p][s] = -EgPieceSquareTable[p-8][flip_square(s)];
1823 /// Position::flipped_copy() makes a copy of the input position, but with
1824 /// the white and black sides reversed. This is only useful for debugging,
1825 /// especially for finding evaluation symmetry bugs.
1827 void Position::flipped_copy(const Position& pos) {
1829 assert(pos.is_ok());
1834 for (Square s = SQ_A1; s <= SQ_H8; s++)
1835 if (!pos.square_is_empty(s))
1836 put_piece(Piece(int(pos.piece_on(s)) ^ 8), flip_square(s));
1839 sideToMove = opposite_color(pos.side_to_move());
1842 if (pos.can_castle_kingside(WHITE)) allow_oo(BLACK);
1843 if (pos.can_castle_queenside(WHITE)) allow_ooo(BLACK);
1844 if (pos.can_castle_kingside(BLACK)) allow_oo(WHITE);
1845 if (pos.can_castle_queenside(BLACK)) allow_ooo(WHITE);
1847 initialKFile = pos.initialKFile;
1848 initialKRFile = pos.initialKRFile;
1849 initialQRFile = pos.initialQRFile;
1851 for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
1852 castleRightsMask[sq] = ALL_CASTLES;
1854 castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO | WHITE_OOO);
1855 castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO | BLACK_OOO);
1856 castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO;
1857 castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO;
1858 castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO;
1859 castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO;
1861 // En passant square
1862 if (pos.st->epSquare != SQ_NONE)
1863 st->epSquare = flip_square(pos.st->epSquare);
1869 st->key = compute_key();
1870 st->pawnKey = compute_pawn_key();
1871 st->materialKey = compute_material_key();
1873 // Incremental scores
1874 st->mgValue = compute_value<MidGame>();
1875 st->egValue = compute_value<EndGame>();
1878 st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
1879 st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
1885 /// Position::is_ok() performs some consitency checks for the position object.
1886 /// This is meant to be helpful when debugging.
1888 bool Position::is_ok(int* failedStep) const {
1890 // What features of the position should be verified?
1891 static const bool debugBitboards = false;
1892 static const bool debugKingCount = false;
1893 static const bool debugKingCapture = false;
1894 static const bool debugCheckerCount = false;
1895 static const bool debugKey = false;
1896 static const bool debugMaterialKey = false;
1897 static const bool debugPawnKey = false;
1898 static const bool debugIncrementalEval = false;
1899 static const bool debugNonPawnMaterial = false;
1900 static const bool debugPieceCounts = false;
1901 static const bool debugPieceList = false;
1903 if (failedStep) *failedStep = 1;
1906 if (!color_is_ok(side_to_move()))
1909 // Are the king squares in the position correct?
1910 if (failedStep) (*failedStep)++;
1911 if (piece_on(king_square(WHITE)) != WK)
1914 if (failedStep) (*failedStep)++;
1915 if (piece_on(king_square(BLACK)) != BK)
1919 if (failedStep) (*failedStep)++;
1920 if (!file_is_ok(initialKRFile))
1923 if (!file_is_ok(initialQRFile))
1926 // Do both sides have exactly one king?
1927 if (failedStep) (*failedStep)++;
1930 int kingCount[2] = {0, 0};
1931 for (Square s = SQ_A1; s <= SQ_H8; s++)
1932 if (type_of_piece_on(s) == KING)
1933 kingCount[color_of_piece_on(s)]++;
1935 if (kingCount[0] != 1 || kingCount[1] != 1)
1939 // Can the side to move capture the opponent's king?
1940 if (failedStep) (*failedStep)++;
1941 if (debugKingCapture)
1943 Color us = side_to_move();
1944 Color them = opposite_color(us);
1945 Square ksq = king_square(them);
1946 if (square_is_attacked(ksq, us))
1950 // Is there more than 2 checkers?
1951 if (failedStep) (*failedStep)++;
1952 if (debugCheckerCount && count_1s(st->checkersBB) > 2)
1956 if (failedStep) (*failedStep)++;
1959 // The intersection of the white and black pieces must be empty
1960 if ((pieces_of_color(WHITE) & pieces_of_color(BLACK)) != EmptyBoardBB)
1963 // The union of the white and black pieces must be equal to all
1965 if ((pieces_of_color(WHITE) | pieces_of_color(BLACK)) != occupied_squares())
1968 // Separate piece type bitboards must have empty intersections
1969 for (PieceType p1 = PAWN; p1 <= KING; p1++)
1970 for (PieceType p2 = PAWN; p2 <= KING; p2++)
1971 if (p1 != p2 && (pieces_of_type(p1) & pieces_of_type(p2)))
1975 // En passant square OK?
1976 if (failedStep) (*failedStep)++;
1977 if (ep_square() != SQ_NONE)
1979 // The en passant square must be on rank 6, from the point of view of the
1981 if (relative_rank(side_to_move(), ep_square()) != RANK_6)
1986 if (failedStep) (*failedStep)++;
1987 if (debugKey && st->key != compute_key())
1990 // Pawn hash key OK?
1991 if (failedStep) (*failedStep)++;
1992 if (debugPawnKey && st->pawnKey != compute_pawn_key())
1995 // Material hash key OK?
1996 if (failedStep) (*failedStep)++;
1997 if (debugMaterialKey && st->materialKey != compute_material_key())
2000 // Incremental eval OK?
2001 if (failedStep) (*failedStep)++;
2002 if (debugIncrementalEval)
2004 if (st->mgValue != compute_value<MidGame>())
2007 if (st->egValue != compute_value<EndGame>())
2011 // Non-pawn material OK?
2012 if (failedStep) (*failedStep)++;
2013 if (debugNonPawnMaterial)
2015 if (st->npMaterial[WHITE] != compute_non_pawn_material(WHITE))
2018 if (st->npMaterial[BLACK] != compute_non_pawn_material(BLACK))
2023 if (failedStep) (*failedStep)++;
2024 if (debugPieceCounts)
2025 for (Color c = WHITE; c <= BLACK; c++)
2026 for (PieceType pt = PAWN; pt <= KING; pt++)
2027 if (pieceCount[c][pt] != count_1s(pieces_of_color_and_type(c, pt)))
2030 if (failedStep) (*failedStep)++;
2033 for(Color c = WHITE; c <= BLACK; c++)
2034 for(PieceType pt = PAWN; pt <= KING; pt++)
2035 for(int i = 0; i < pieceCount[c][pt]; i++)
2037 if (piece_on(piece_list(c, pt, i)) != piece_of_color_and_type(c, pt))
2040 if (index[piece_list(c, pt, i)] != i)
2044 if (failedStep) *failedStep = 0;