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 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/>.
36 #include "ucioption.h"
43 extern SearchStack EmptySearchStack;
45 int Position::castleRightsMask[64];
47 Key Position::zobrist[2][8][64];
48 Key Position::zobEp[64];
49 Key Position::zobCastle[16];
50 Key Position::zobMaterial[2][8][16];
51 Key Position::zobSideToMove;
53 Value Position::MgPieceSquareTable[16][64];
54 Value Position::EgPieceSquareTable[16][64];
56 static bool RequestPending = false;
64 Position::Position(const Position& pos) {
68 Position::Position(const std::string& fen) {
73 /// Position::from_fen() initializes the position object with the given FEN
74 /// string. This function is not very robust - make sure that input FENs are
75 /// correct (this is assumed to be the responsibility of the GUI).
77 void Position::from_fen(const std::string& fen) {
79 static const std::string pieceLetters = "KQRBNPkqrbnp";
80 static const Piece pieces[] = { WK, WQ, WR, WB, WN, WP, BK, BQ, BR, BB, BN, BP };
88 for ( ; fen[i] != ' '; i++)
92 // Skip the given number of files
93 file += (fen[i] - '1' + 1);
96 else if (fen[i] == '/')
102 size_t idx = pieceLetters.find(fen[i]);
103 if (idx == std::string::npos)
105 std::cout << "Error in FEN at character " << i << std::endl;
108 Square square = make_square(file, rank);
109 put_piece(pieces[idx], square);
115 if (fen[i] != 'w' && fen[i] != 'b')
117 std::cout << "Error in FEN at character " << i << std::endl;
120 sideToMove = (fen[i] == 'w' ? WHITE : BLACK);
126 std::cout << "Error in FEN at character " << i << std::endl;
131 while(strchr("KQkqabcdefghABCDEFGH-", fen[i])) {
137 else if(fen[i] == 'K') allow_oo(WHITE);
138 else if(fen[i] == 'Q') allow_ooo(WHITE);
139 else if(fen[i] == 'k') allow_oo(BLACK);
140 else if(fen[i] == 'q') allow_ooo(BLACK);
141 else if(fen[i] >= 'A' && fen[i] <= 'H') {
142 File rookFile, kingFile = FILE_NONE;
143 for(Square square = SQ_B1; square <= SQ_G1; square++)
144 if(piece_on(square) == WK)
145 kingFile = square_file(square);
146 if(kingFile == FILE_NONE) {
147 std::cout << "Error in FEN at character " << i << std::endl;
150 initialKFile = kingFile;
151 rookFile = File(fen[i] - 'A') + FILE_A;
152 if(rookFile < initialKFile) {
154 initialQRFile = rookFile;
158 initialKRFile = rookFile;
161 else if(fen[i] >= 'a' && fen[i] <= 'h') {
162 File rookFile, kingFile = FILE_NONE;
163 for(Square square = SQ_B8; square <= SQ_G8; square++)
164 if(piece_on(square) == BK)
165 kingFile = square_file(square);
166 if(kingFile == FILE_NONE) {
167 std::cout << "Error in FEN at character " << i << std::endl;
170 initialKFile = kingFile;
171 rookFile = File(fen[i] - 'a') + FILE_A;
172 if(rookFile < initialKFile) {
174 initialQRFile = rookFile;
178 initialKRFile = rookFile;
182 std::cout << "Error in FEN at character " << i << std::endl;
189 while (fen[i] == ' ')
193 if ( i <= fen.length() - 2
194 && (fen[i] >= 'a' && fen[i] <= 'h')
195 && (fen[i+1] == '3' || fen[i+1] == '6'))
196 st->epSquare = square_from_string(fen.substr(i, 2));
198 // Various initialisation
199 for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
200 castleRightsMask[sq] = ALL_CASTLES;
202 castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO|WHITE_OOO);
203 castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO|BLACK_OOO);
204 castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO;
205 castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO;
206 castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO;
207 castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO;
211 st->key = compute_key();
212 st->pawnKey = compute_pawn_key();
213 st->materialKey = compute_material_key();
214 st->mgValue = compute_value<MidGame>();
215 st->egValue = compute_value<EndGame>();
216 npMaterial[WHITE] = compute_non_pawn_material(WHITE);
217 npMaterial[BLACK] = compute_non_pawn_material(BLACK);
221 /// Position::to_fen() converts the position object to a FEN string. This is
222 /// probably only useful for debugging.
224 const std::string Position::to_fen() const {
226 static const std::string pieceLetters = " PNBRQK pnbrqk";
230 for (Rank rank = RANK_8; rank >= RANK_1; rank--)
233 for (File file = FILE_A; file <= FILE_H; file++)
235 Square sq = make_square(file, rank);
236 if (!square_is_occupied(sq))
242 fen += (char)skip + '0';
245 fen += pieceLetters[piece_on(sq)];
248 fen += (char)skip + '0';
250 fen += (rank > RANK_1 ? '/' : ' ');
252 fen += (sideToMove == WHITE ? "w " : "b ");
253 if (st->castleRights != NO_CASTLES)
255 if (can_castle_kingside(WHITE)) fen += 'K';
256 if (can_castle_queenside(WHITE)) fen += 'Q';
257 if (can_castle_kingside(BLACK)) fen += 'k';
258 if (can_castle_queenside(BLACK)) fen += 'q';
263 if (ep_square() != SQ_NONE)
264 fen += square_to_string(ep_square());
272 /// Position::print() prints an ASCII representation of the position to
273 /// the standard output. If a move is given then also the san is print.
275 void Position::print(Move m) const {
277 static const std::string pieceLetters = " PNBRQK PNBRQK .";
279 // Check for reentrancy, as example when called from inside
280 // MovePicker that is used also here in move_to_san()
284 RequestPending = true;
286 std::cout << std::endl;
289 std::string col = (color_of_piece_on(move_from(m)) == BLACK ? ".." : "");
290 std::cout << "Move is: " << col << move_to_san(*this, m) << std::endl;
292 for (Rank rank = RANK_8; rank >= RANK_1; rank--)
294 std::cout << "+---+---+---+---+---+---+---+---+" << std::endl;
295 for (File file = FILE_A; file <= FILE_H; file++)
297 Square sq = make_square(file, rank);
298 Piece piece = piece_on(sq);
299 if (piece == EMPTY && square_color(sq) == WHITE)
302 char col = (color_of_piece_on(sq) == BLACK ? '=' : ' ');
303 std::cout << '|' << col << pieceLetters[piece] << col;
305 std::cout << '|' << std::endl;
307 std::cout << "+---+---+---+---+---+---+---+---+" << std::endl
308 << "Fen is: " << to_fen() << std::endl
309 << "Key is: " << st->key << std::endl;
311 RequestPending = false;
315 /// Position::copy() creates a copy of the input position.
317 void Position::copy(const Position &pos) {
319 memcpy(this, &pos, sizeof(Position));
323 /// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
324 /// king) pieces for the given color and for the given pinner type. Or, when
325 /// template parameter FindPinned is false, the pieces of the given color
326 /// candidate for a discovery check against the enemy king.
327 /// Note that checkersBB bitboard must be already updated.
329 template<bool FindPinned>
330 Bitboard Position::hidden_checkers(Color c) const {
332 Bitboard pinners, result = EmptyBoardBB;
334 // Pinned pieces protect our king, dicovery checks attack
336 Square ksq = king_square(FindPinned ? c : opposite_color(c));
338 // Pinners are sliders, not checkers, that give check when
339 // candidate pinned is removed.
340 pinners = (rooks_and_queens(FindPinned ? opposite_color(c) : c) & RookPseudoAttacks[ksq])
341 | (bishops_and_queens(FindPinned ? opposite_color(c) : c) & BishopPseudoAttacks[ksq]);
343 if (FindPinned && pinners)
344 pinners &= ~st->checkersBB;
348 Square s = pop_1st_bit(&pinners);
349 Bitboard b = squares_between(s, ksq) & occupied_squares();
353 if ( !(b & (b - 1)) // Only one bit set?
354 && (b & pieces_of_color(c))) // Is an our piece?
361 /// Position:pinned_pieces() returns a bitboard of all pinned (against the
362 /// king) pieces for the given color.
364 Bitboard Position::pinned_pieces(Color c) const {
366 return hidden_checkers<true>(c);
370 /// Position:discovered_check_candidates() returns a bitboard containing all
371 /// pieces for the given side which are candidates for giving a discovered
374 Bitboard Position::discovered_check_candidates(Color c) const {
376 return hidden_checkers<false>(c);
379 /// Position::attacks_to() computes a bitboard containing all pieces which
380 /// attacks a given square. There are two versions of this function: One
381 /// which finds attackers of both colors, and one which only finds the
382 /// attackers for one side.
384 Bitboard Position::attacks_to(Square s) const {
386 return (pawn_attacks(BLACK, s) & pawns(WHITE))
387 | (pawn_attacks(WHITE, s) & pawns(BLACK))
388 | (piece_attacks<KNIGHT>(s) & pieces_of_type(KNIGHT))
389 | (piece_attacks<ROOK>(s) & rooks_and_queens())
390 | (piece_attacks<BISHOP>(s) & bishops_and_queens())
391 | (piece_attacks<KING>(s) & pieces_of_type(KING));
394 /// Position::piece_attacks_square() tests whether the piece on square f
395 /// attacks square t.
397 bool Position::piece_attacks_square(Piece p, Square f, Square t) const {
399 assert(square_is_ok(f));
400 assert(square_is_ok(t));
404 case WP: return pawn_attacks_square(WHITE, f, t);
405 case BP: return pawn_attacks_square(BLACK, f, t);
406 case WN: case BN: return piece_attacks_square<KNIGHT>(f, t);
407 case WB: case BB: return piece_attacks_square<BISHOP>(f, t);
408 case WR: case BR: return piece_attacks_square<ROOK>(f, t);
409 case WQ: case BQ: return piece_attacks_square<QUEEN>(f, t);
410 case WK: case BK: return piece_attacks_square<KING>(f, t);
417 /// Position::move_attacks_square() tests whether a move from the current
418 /// position attacks a given square.
420 bool Position::move_attacks_square(Move m, Square s) const {
422 assert(move_is_ok(m));
423 assert(square_is_ok(s));
425 Square f = move_from(m), t = move_to(m);
427 assert(square_is_occupied(f));
429 if (piece_attacks_square(piece_on(f), t, s))
432 // Move the piece and scan for X-ray attacks behind it
433 Bitboard occ = occupied_squares();
434 Color us = color_of_piece_on(f);
437 Bitboard xray = ( (rook_attacks_bb(s, occ) & rooks_and_queens())
438 |(bishop_attacks_bb(s, occ) & bishops_and_queens())) & pieces_of_color(us);
440 // If we have attacks we need to verify that are caused by our move
441 // and are not already existent ones.
442 return xray && (xray ^ (xray & piece_attacks<QUEEN>(s)));
446 /// Position::find_checkers() computes the checkersBB bitboard, which
447 /// contains a nonzero bit for each checking piece (0, 1 or 2). It
448 /// currently works by calling Position::attacks_to, which is probably
449 /// inefficient. Consider rewriting this function to use the last move
450 /// played, like in non-bitboard versions of Glaurung.
452 void Position::find_checkers() {
454 Color us = side_to_move();
455 st->checkersBB = attacks_to(king_square(us), opposite_color(us));
459 /// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
461 bool Position::pl_move_is_legal(Move m) const {
463 return pl_move_is_legal(m, pinned_pieces(side_to_move()));
466 bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
469 assert(move_is_ok(m));
470 assert(pinned == pinned_pieces(side_to_move()));
472 // If we're in check, all pseudo-legal moves are legal, because our
473 // check evasion generator only generates true legal moves.
477 // Castling moves are checked for legality during move generation.
478 if (move_is_castle(m))
481 Color us = side_to_move();
482 Square from = move_from(m);
483 Square ksq = king_square(us);
485 assert(color_of_piece_on(from) == us);
486 assert(piece_on(ksq) == piece_of_color_and_type(us, KING));
488 // En passant captures are a tricky special case. Because they are
489 // rather uncommon, we do it simply by testing whether the king is attacked
490 // after the move is made
493 Color them = opposite_color(us);
494 Square to = move_to(m);
495 Square capsq = make_square(square_file(to), square_rank(from));
496 Bitboard b = occupied_squares();
498 assert(to == ep_square());
499 assert(piece_on(from) == piece_of_color_and_type(us, PAWN));
500 assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN));
501 assert(piece_on(to) == EMPTY);
504 clear_bit(&b, capsq);
507 return !(rook_attacks_bb(ksq, b) & rooks_and_queens(them))
508 && !(bishop_attacks_bb(ksq, b) & bishops_and_queens(them));
511 // If the moving piece is a king, check whether the destination
512 // square is attacked by the opponent.
514 return !(square_is_attacked(move_to(m), opposite_color(us)));
516 // A non-king move is legal if and only if it is not pinned or it
517 // is moving along the ray towards or away from the king.
519 || !bit_is_set(pinned, from)
520 || (direction_between_squares(from, ksq) == direction_between_squares(move_to(m), ksq)));
524 /// Position::move_is_check() tests whether a pseudo-legal move is a check
526 bool Position::move_is_check(Move m) const {
528 Bitboard dc = discovered_check_candidates(side_to_move());
529 return move_is_check(m, dc);
532 bool Position::move_is_check(Move m, Bitboard dcCandidates) const {
535 assert(move_is_ok(m));
536 assert(dcCandidates == discovered_check_candidates(side_to_move()));
538 Color us = side_to_move();
539 Color them = opposite_color(us);
540 Square from = move_from(m);
541 Square to = move_to(m);
542 Square ksq = king_square(them);
544 assert(color_of_piece_on(from) == us);
545 assert(piece_on(ksq) == piece_of_color_and_type(them, KING));
547 // Proceed according to the type of the moving piece
548 switch (type_of_piece_on(from))
552 if (bit_is_set(pawn_attacks(them, ksq), to)) // Normal check?
555 if ( dcCandidates // Discovered check?
556 && bit_is_set(dcCandidates, from)
557 && (direction_between_squares(from, ksq) != direction_between_squares(to, ksq)))
560 if (move_promotion(m)) // Promotion with check?
562 Bitboard b = occupied_squares();
565 switch (move_promotion(m))
568 return bit_is_set(piece_attacks<KNIGHT>(to), ksq);
570 return bit_is_set(bishop_attacks_bb(to, b), ksq);
572 return bit_is_set(rook_attacks_bb(to, b), ksq);
574 return bit_is_set(queen_attacks_bb(to, b), ksq);
579 // En passant capture with check? We have already handled the case
580 // of direct checks and ordinary discovered check, the only case we
581 // need to handle is the unusual case of a discovered check through the
583 else if (move_is_ep(m))
585 Square capsq = make_square(square_file(to), square_rank(from));
586 Bitboard b = occupied_squares();
588 clear_bit(&b, capsq);
590 return (rook_attacks_bb(ksq, b) & rooks_and_queens(us))
591 ||(bishop_attacks_bb(ksq, b) & bishops_and_queens(us));
595 // Test discovered check and normal check according to piece type
597 return (dcCandidates && bit_is_set(dcCandidates, from))
598 || bit_is_set(piece_attacks<KNIGHT>(ksq), to);
601 return (dcCandidates && bit_is_set(dcCandidates, from))
602 || (direction_is_diagonal(ksq, to) && bit_is_set(piece_attacks<BISHOP>(ksq), to));
605 return (dcCandidates && bit_is_set(dcCandidates, from))
606 || (direction_is_straight(ksq, to) && bit_is_set(piece_attacks<ROOK>(ksq), to));
609 // Discovered checks are impossible!
610 assert(!bit_is_set(dcCandidates, from));
611 return ( (direction_is_straight(ksq, to) && bit_is_set(piece_attacks<ROOK>(ksq), to))
612 || (direction_is_diagonal(ksq, to) && bit_is_set(piece_attacks<BISHOP>(ksq), to)));
616 if ( bit_is_set(dcCandidates, from)
617 && (direction_between_squares(from, ksq) != direction_between_squares(to, ksq)))
620 // Castling with check?
621 if (move_is_castle(m))
623 Square kfrom, kto, rfrom, rto;
624 Bitboard b = occupied_squares();
630 kto = relative_square(us, SQ_G1);
631 rto = relative_square(us, SQ_F1);
633 kto = relative_square(us, SQ_C1);
634 rto = relative_square(us, SQ_D1);
636 clear_bit(&b, kfrom);
637 clear_bit(&b, rfrom);
640 return bit_is_set(rook_attacks_bb(rto, b), ksq);
644 default: // NO_PIECE_TYPE
652 /// Position::update_checkers() udpates chekers info given the move. It is called
653 /// in do_move() and is faster then find_checkers().
655 template<PieceType Piece>
656 inline void Position::update_checkers(Bitboard* pCheckersBB, Square ksq, Square from,
657 Square to, Bitboard dcCandidates) {
659 const bool Bishop = (Piece == QUEEN || Piece == BISHOP);
660 const bool Rook = (Piece == QUEEN || Piece == ROOK);
661 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);
673 if (Piece != QUEEN && bit_is_set(dcCandidates, from))
676 (*pCheckersBB) |= (piece_attacks<ROOK>(ksq) & rooks_and_queens(side_to_move()));
679 (*pCheckersBB) |= (piece_attacks<BISHOP>(ksq) & bishops_and_queens(side_to_move()));
684 /// Position::do_move() makes a move, and saves all information necessary
685 /// to a StateInfo object. The move is assumed to be legal.
686 /// Pseudo-legal moves should be filtered out before this function is called.
688 void Position::do_move(Move m, StateInfo& newSt) {
690 do_move(m, newSt, discovered_check_candidates(side_to_move()));
693 void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
696 assert(move_is_ok(m));
698 // Copy some fields of old state to our new StateInfo object except the
699 // ones which are recalculated from scratch anyway, then switch our state
700 // pointer to point to the new, ready to be updated, state.
701 struct ReducedStateInfo {
702 Key key, pawnKey, materialKey;
703 int castleRights, rule50;
705 Value mgValue, egValue;
708 memcpy(&newSt, st, sizeof(ReducedStateInfo));
709 newSt.capture = NO_PIECE_TYPE;
713 // Save the current key to the history[] array, in order to be able to
714 // detect repetition draws.
715 history[gamePly] = st->key;
717 // Increment the 50 moves rule draw counter. Resetting it to zero in the
718 // case of non-reversible moves is taken care of later.
721 if (move_is_castle(m))
723 else if (move_promotion(m))
724 do_promotion_move(m);
725 else if (move_is_ep(m))
729 Color us = side_to_move();
730 Color them = opposite_color(us);
731 Square from = move_from(m);
732 Square to = move_to(m);
734 assert(color_of_piece_on(from) == us);
735 assert(color_of_piece_on(to) == them || piece_on(to) == EMPTY);
737 PieceType piece = type_of_piece_on(from);
739 st->capture = type_of_piece_on(to);
742 do_capture_move(st->capture, them, to);
745 clear_bit(&(byColorBB[us]), from);
746 clear_bit(&(byTypeBB[piece]), from);
747 clear_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
748 set_bit(&(byColorBB[us]), to);
749 set_bit(&(byTypeBB[piece]), to);
750 set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
751 board[to] = board[from];
755 st->key ^= zobrist[us][piece][from] ^ zobrist[us][piece][to];
757 // Update incremental scores
758 st->mgValue -= pst<MidGame>(us, piece, from);
759 st->mgValue += pst<MidGame>(us, piece, to);
760 st->egValue -= pst<EndGame>(us, piece, from);
761 st->egValue += pst<EndGame>(us, piece, to);
763 // If the moving piece was a king, update the king square
767 // Reset en passant square
768 if (st->epSquare != SQ_NONE)
770 st->key ^= zobEp[st->epSquare];
771 st->epSquare = SQ_NONE;
774 // If the moving piece was a pawn do some special extra work
777 // Reset rule 50 draw counter
780 // Update pawn hash key
781 st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
783 // Set en passant square, only if moved pawn can be captured
784 if (abs(int(to) - int(from)) == 16)
786 if ( (us == WHITE && (pawn_attacks(WHITE, from + DELTA_N) & pawns(BLACK)))
787 || (us == BLACK && (pawn_attacks(BLACK, from + DELTA_S) & pawns(WHITE))))
789 st->epSquare = Square((int(from) + int(to)) / 2);
790 st->key ^= zobEp[st->epSquare];
795 // Update piece lists
796 pieceList[us][piece][index[from]] = to;
797 index[to] = index[from];
799 // Update castle rights
800 st->key ^= zobCastle[st->castleRights];
801 st->castleRights &= castleRightsMask[from];
802 st->castleRights &= castleRightsMask[to];
803 st->key ^= zobCastle[st->castleRights];
805 // Update checkers bitboard, piece must be already moved
806 st->checkersBB = EmptyBoardBB;
807 Square ksq = king_square(them);
810 case PAWN: update_checkers<PAWN>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
811 case KNIGHT: update_checkers<KNIGHT>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
812 case BISHOP: update_checkers<BISHOP>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
813 case ROOK: update_checkers<ROOK>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
814 case QUEEN: update_checkers<QUEEN>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
815 case KING: update_checkers<KING>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
816 default: assert(false); break;
821 st->key ^= zobSideToMove;
822 sideToMove = opposite_color(sideToMove);
825 st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
826 st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
832 /// Position::do_capture_move() is a private method used to update captured
833 /// piece info. It is called from the main Position::do_move function.
835 void Position::do_capture_move(PieceType capture, Color them, Square to) {
837 assert(capture != KING);
839 // Remove captured piece
840 clear_bit(&(byColorBB[them]), to);
841 clear_bit(&(byTypeBB[capture]), to);
844 st->key ^= zobrist[them][capture][to];
846 // If the captured piece was a pawn, update pawn hash key
848 st->pawnKey ^= zobrist[them][PAWN][to];
850 // Update incremental scores
851 st->mgValue -= pst<MidGame>(them, capture, to);
852 st->egValue -= pst<EndGame>(them, capture, to);
856 npMaterial[them] -= piece_value_midgame(capture);
858 // Update material hash key
859 st->materialKey ^= zobMaterial[them][capture][pieceCount[them][capture]];
861 // Update piece count
862 pieceCount[them][capture]--;
865 pieceList[them][capture][index[to]] = pieceList[them][capture][pieceCount[them][capture]];
866 index[pieceList[them][capture][index[to]]] = index[to];
868 // Reset rule 50 counter
873 /// Position::do_castle_move() is a private method used to make a castling
874 /// move. It is called from the main Position::do_move function. Note that
875 /// castling moves are encoded as "king captures friendly rook" moves, for
876 /// instance white short castling in a non-Chess960 game is encoded as e1h1.
878 void Position::do_castle_move(Move m) {
881 assert(move_is_ok(m));
882 assert(move_is_castle(m));
884 Color us = side_to_move();
885 Color them = opposite_color(us);
887 // Find source squares for king and rook
888 Square kfrom = move_from(m);
889 Square rfrom = move_to(m); // HACK: See comment at beginning of function
892 assert(piece_on(kfrom) == piece_of_color_and_type(us, KING));
893 assert(piece_on(rfrom) == piece_of_color_and_type(us, ROOK));
895 // Find destination squares for king and rook
896 if (rfrom > kfrom) // O-O
898 kto = relative_square(us, SQ_G1);
899 rto = relative_square(us, SQ_F1);
901 kto = relative_square(us, SQ_C1);
902 rto = relative_square(us, SQ_D1);
905 // Remove pieces from source squares
906 clear_bit(&(byColorBB[us]), kfrom);
907 clear_bit(&(byTypeBB[KING]), kfrom);
908 clear_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares
909 clear_bit(&(byColorBB[us]), rfrom);
910 clear_bit(&(byTypeBB[ROOK]), rfrom);
911 clear_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares
913 // Put pieces on destination squares
914 set_bit(&(byColorBB[us]), kto);
915 set_bit(&(byTypeBB[KING]), kto);
916 set_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares
917 set_bit(&(byColorBB[us]), rto);
918 set_bit(&(byTypeBB[ROOK]), rto);
919 set_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
921 // Update board array
922 board[kfrom] = board[rfrom] = EMPTY;
923 board[kto] = piece_of_color_and_type(us, KING);
924 board[rto] = piece_of_color_and_type(us, ROOK);
926 // Update king square
927 kingSquare[us] = kto;
929 // Update piece lists
930 pieceList[us][KING][index[kfrom]] = kto;
931 pieceList[us][ROOK][index[rfrom]] = rto;
932 int tmp = index[rfrom];
933 index[kto] = index[kfrom];
936 // Update incremental scores
937 st->mgValue -= pst<MidGame>(us, KING, kfrom);
938 st->mgValue += pst<MidGame>(us, KING, kto);
939 st->egValue -= pst<EndGame>(us, KING, kfrom);
940 st->egValue += pst<EndGame>(us, KING, kto);
941 st->mgValue -= pst<MidGame>(us, ROOK, rfrom);
942 st->mgValue += pst<MidGame>(us, ROOK, rto);
943 st->egValue -= pst<EndGame>(us, ROOK, rfrom);
944 st->egValue += pst<EndGame>(us, ROOK, rto);
947 st->key ^= zobrist[us][KING][kfrom] ^ zobrist[us][KING][kto];
948 st->key ^= zobrist[us][ROOK][rfrom] ^ zobrist[us][ROOK][rto];
950 // Clear en passant square
951 if (st->epSquare != SQ_NONE)
953 st->key ^= zobEp[st->epSquare];
954 st->epSquare = SQ_NONE;
957 // Update castling rights
958 st->key ^= zobCastle[st->castleRights];
959 st->castleRights &= castleRightsMask[kfrom];
960 st->key ^= zobCastle[st->castleRights];
962 // Reset rule 50 counter
965 // Update checkers BB
966 st->checkersBB = attacks_to(king_square(them), us);
970 /// Position::do_promotion_move() is a private method used to make a promotion
971 /// move. It is called from the main Position::do_move function.
973 void Position::do_promotion_move(Move m) {
980 assert(move_is_ok(m));
981 assert(move_promotion(m));
984 them = opposite_color(us);
988 assert(relative_rank(us, to) == RANK_8);
989 assert(piece_on(from) == piece_of_color_and_type(us, PAWN));
990 assert(color_of_piece_on(to) == them || square_is_empty(to));
992 st->capture = type_of_piece_on(to);
995 do_capture_move(st->capture, them, to);
998 clear_bit(&(byColorBB[us]), from);
999 clear_bit(&(byTypeBB[PAWN]), from);
1000 clear_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
1001 board[from] = EMPTY;
1003 // Insert promoted piece
1004 promotion = move_promotion(m);
1005 assert(promotion >= KNIGHT && promotion <= QUEEN);
1006 set_bit(&(byColorBB[us]), to);
1007 set_bit(&(byTypeBB[promotion]), to);
1008 set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
1009 board[to] = piece_of_color_and_type(us, promotion);
1012 st->key ^= zobrist[us][PAWN][from] ^ zobrist[us][promotion][to];
1014 // Update pawn hash key
1015 st->pawnKey ^= zobrist[us][PAWN][from];
1017 // Update material key
1018 st->materialKey ^= zobMaterial[us][PAWN][pieceCount[us][PAWN]];
1019 st->materialKey ^= zobMaterial[us][promotion][pieceCount[us][promotion]+1];
1021 // Update piece counts
1022 pieceCount[us][PAWN]--;
1023 pieceCount[us][promotion]++;
1025 // Update piece lists
1026 pieceList[us][PAWN][index[from]] = pieceList[us][PAWN][pieceCount[us][PAWN]];
1027 index[pieceList[us][PAWN][index[from]]] = index[from];
1028 pieceList[us][promotion][pieceCount[us][promotion] - 1] = to;
1029 index[to] = pieceCount[us][promotion] - 1;
1031 // Update incremental scores
1032 st->mgValue -= pst<MidGame>(us, PAWN, from);
1033 st->mgValue += pst<MidGame>(us, promotion, to);
1034 st->egValue -= pst<EndGame>(us, PAWN, from);
1035 st->egValue += pst<EndGame>(us, promotion, to);
1038 npMaterial[us] += piece_value_midgame(promotion);
1040 // Clear the en passant square
1041 if (st->epSquare != SQ_NONE)
1043 st->key ^= zobEp[st->epSquare];
1044 st->epSquare = SQ_NONE;
1047 // Update castle rights
1048 st->key ^= zobCastle[st->castleRights];
1049 st->castleRights &= castleRightsMask[to];
1050 st->key ^= zobCastle[st->castleRights];
1052 // Reset rule 50 counter
1055 // Update checkers BB
1056 st->checkersBB = attacks_to(king_square(them), us);
1060 /// Position::do_ep_move() is a private method used to make an en passant
1061 /// capture. It is called from the main Position::do_move function.
1063 void Position::do_ep_move(Move m) {
1066 Square from, to, capsq;
1069 assert(move_is_ok(m));
1070 assert(move_is_ep(m));
1072 us = side_to_move();
1073 them = opposite_color(us);
1074 from = move_from(m);
1076 capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
1078 assert(to == st->epSquare);
1079 assert(relative_rank(us, to) == RANK_6);
1080 assert(piece_on(to) == EMPTY);
1081 assert(piece_on(from) == piece_of_color_and_type(us, PAWN));
1082 assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN));
1084 // Remove captured piece
1085 clear_bit(&(byColorBB[them]), capsq);
1086 clear_bit(&(byTypeBB[PAWN]), capsq);
1087 clear_bit(&(byTypeBB[0]), capsq); // HACK: byTypeBB[0] == occupied squares
1088 board[capsq] = EMPTY;
1090 // Remove moving piece from source square
1091 clear_bit(&(byColorBB[us]), from);
1092 clear_bit(&(byTypeBB[PAWN]), from);
1093 clear_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
1095 // Put moving piece on destination square
1096 set_bit(&(byColorBB[us]), to);
1097 set_bit(&(byTypeBB[PAWN]), to);
1098 set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
1099 board[to] = board[from];
1100 board[from] = EMPTY;
1102 // Update material hash key
1103 st->materialKey ^= zobMaterial[them][PAWN][pieceCount[them][PAWN]];
1105 // Update piece count
1106 pieceCount[them][PAWN]--;
1108 // Update piece list
1109 pieceList[us][PAWN][index[from]] = to;
1110 index[to] = index[from];
1111 pieceList[them][PAWN][index[capsq]] = pieceList[them][PAWN][pieceCount[them][PAWN]];
1112 index[pieceList[them][PAWN][index[capsq]]] = index[capsq];
1115 st->key ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
1116 st->key ^= zobrist[them][PAWN][capsq];
1117 st->key ^= zobEp[st->epSquare];
1119 // Update pawn hash key
1120 st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
1121 st->pawnKey ^= zobrist[them][PAWN][capsq];
1123 // Update incremental scores
1124 st->mgValue -= pst<MidGame>(them, PAWN, capsq);
1125 st->mgValue -= pst<MidGame>(us, PAWN, from);
1126 st->mgValue += pst<MidGame>(us, PAWN, to);
1127 st->egValue -= pst<EndGame>(them, PAWN, capsq);
1128 st->egValue -= pst<EndGame>(us, PAWN, from);
1129 st->egValue += pst<EndGame>(us, PAWN, to);
1131 // Reset en passant square
1132 st->epSquare = SQ_NONE;
1134 // Reset rule 50 counter
1137 // Update checkers BB
1138 st->checkersBB = attacks_to(king_square(them), us);
1142 /// Position::undo_move() unmakes a move. When it returns, the position should
1143 /// be restored to exactly the same state as before the move was made.
1145 void Position::undo_move(Move m) {
1148 assert(move_is_ok(m));
1151 sideToMove = opposite_color(sideToMove);
1153 if (move_is_castle(m))
1154 undo_castle_move(m);
1155 else if (move_promotion(m))
1156 undo_promotion_move(m);
1157 else if (move_is_ep(m))
1165 us = side_to_move();
1166 them = opposite_color(us);
1167 from = move_from(m);
1170 assert(piece_on(from) == EMPTY);
1171 assert(color_of_piece_on(to) == us);
1173 // Put the piece back at the source square
1174 piece = type_of_piece_on(to);
1175 set_bit(&(byColorBB[us]), from);
1176 set_bit(&(byTypeBB[piece]), from);
1177 set_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
1178 board[from] = piece_of_color_and_type(us, piece);
1180 // Clear the destination square
1181 clear_bit(&(byColorBB[us]), to);
1182 clear_bit(&(byTypeBB[piece]), to);
1183 clear_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
1185 // If the moving piece was a king, update the king square
1187 kingSquare[us] = from;
1189 // Update piece list
1190 pieceList[us][piece][index[to]] = from;
1191 index[from] = index[to];
1195 assert(st->capture != KING);
1197 // Replace the captured piece
1198 set_bit(&(byColorBB[them]), to);
1199 set_bit(&(byTypeBB[st->capture]), to);
1200 set_bit(&(byTypeBB[0]), to);
1201 board[to] = piece_of_color_and_type(them, st->capture);
1204 if (st->capture != PAWN)
1205 npMaterial[them] += piece_value_midgame(st->capture);
1207 // Update piece list
1208 pieceList[them][st->capture][pieceCount[them][st->capture]] = to;
1209 index[to] = pieceCount[them][st->capture];
1211 // Update piece count
1212 pieceCount[them][st->capture]++;
1217 // Finally point our state pointer back to the previous state
1224 /// Position::undo_castle_move() is a private method used to unmake a castling
1225 /// move. It is called from the main Position::undo_move function. Note that
1226 /// castling moves are encoded as "king captures friendly rook" moves, for
1227 /// instance white short castling in a non-Chess960 game is encoded as e1h1.
1229 void Position::undo_castle_move(Move m) {
1231 assert(move_is_ok(m));
1232 assert(move_is_castle(m));
1234 // When we have arrived here, some work has already been done by
1235 // Position::undo_move. In particular, the side to move has been switched,
1236 // so the code below is correct.
1237 Color us = side_to_move();
1239 // Find source squares for king and rook
1240 Square kfrom = move_from(m);
1241 Square rfrom = move_to(m); // HACK: See comment at beginning of function
1244 // Find destination squares for king and rook
1245 if (rfrom > kfrom) // O-O
1247 kto = relative_square(us, SQ_G1);
1248 rto = relative_square(us, SQ_F1);
1250 kto = relative_square(us, SQ_C1);
1251 rto = relative_square(us, SQ_D1);
1254 assert(piece_on(kto) == piece_of_color_and_type(us, KING));
1255 assert(piece_on(rto) == piece_of_color_and_type(us, ROOK));
1257 // Remove pieces from destination squares
1258 clear_bit(&(byColorBB[us]), kto);
1259 clear_bit(&(byTypeBB[KING]), kto);
1260 clear_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares
1261 clear_bit(&(byColorBB[us]), rto);
1262 clear_bit(&(byTypeBB[ROOK]), rto);
1263 clear_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
1265 // Put pieces on source squares
1266 set_bit(&(byColorBB[us]), kfrom);
1267 set_bit(&(byTypeBB[KING]), kfrom);
1268 set_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares
1269 set_bit(&(byColorBB[us]), rfrom);
1270 set_bit(&(byTypeBB[ROOK]), rfrom);
1271 set_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares
1274 board[rto] = board[kto] = EMPTY;
1275 board[rfrom] = piece_of_color_and_type(us, ROOK);
1276 board[kfrom] = piece_of_color_and_type(us, KING);
1278 // Update king square
1279 kingSquare[us] = kfrom;
1281 // Update piece lists
1282 pieceList[us][KING][index[kto]] = kfrom;
1283 pieceList[us][ROOK][index[rto]] = rfrom;
1284 int tmp = index[rto]; // Necessary because we may have rto == kfrom in FRC.
1285 index[kfrom] = index[kto];
1290 /// Position::undo_promotion_move() is a private method used to unmake a
1291 /// promotion move. It is called from the main Position::do_move
1294 void Position::undo_promotion_move(Move m) {
1298 PieceType promotion;
1300 assert(move_is_ok(m));
1301 assert(move_promotion(m));
1303 // When we have arrived here, some work has already been done by
1304 // Position::undo_move. In particular, the side to move has been switched,
1305 // so the code below is correct.
1306 us = side_to_move();
1307 them = opposite_color(us);
1308 from = move_from(m);
1311 assert(relative_rank(us, to) == RANK_8);
1312 assert(piece_on(from) == EMPTY);
1314 // Remove promoted piece
1315 promotion = move_promotion(m);
1316 assert(piece_on(to)==piece_of_color_and_type(us, promotion));
1317 assert(promotion >= KNIGHT && promotion <= QUEEN);
1318 clear_bit(&(byColorBB[us]), to);
1319 clear_bit(&(byTypeBB[promotion]), to);
1320 clear_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
1322 // Insert pawn at source square
1323 set_bit(&(byColorBB[us]), from);
1324 set_bit(&(byTypeBB[PAWN]), from);
1325 set_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
1326 board[from] = piece_of_color_and_type(us, PAWN);
1329 npMaterial[us] -= piece_value_midgame(promotion);
1331 // Update piece list
1332 pieceList[us][PAWN][pieceCount[us][PAWN]] = from;
1333 index[from] = pieceCount[us][PAWN];
1334 pieceList[us][promotion][index[to]] =
1335 pieceList[us][promotion][pieceCount[us][promotion] - 1];
1336 index[pieceList[us][promotion][index[to]]] = index[to];
1338 // Update piece counts
1339 pieceCount[us][promotion]--;
1340 pieceCount[us][PAWN]++;
1344 assert(st->capture != KING);
1346 // Insert captured piece:
1347 set_bit(&(byColorBB[them]), to);
1348 set_bit(&(byTypeBB[st->capture]), to);
1349 set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
1350 board[to] = piece_of_color_and_type(them, st->capture);
1352 // Update material. Because the move is a promotion move, we know
1353 // that the captured piece cannot be a pawn.
1354 assert(st->capture != PAWN);
1355 npMaterial[them] += piece_value_midgame(st->capture);
1357 // Update piece list
1358 pieceList[them][st->capture][pieceCount[them][st->capture]] = to;
1359 index[to] = pieceCount[them][st->capture];
1361 // Update piece count
1362 pieceCount[them][st->capture]++;
1368 /// Position::undo_ep_move() is a private method used to unmake an en passant
1369 /// capture. It is called from the main Position::undo_move function.
1371 void Position::undo_ep_move(Move m) {
1373 assert(move_is_ok(m));
1374 assert(move_is_ep(m));
1376 // When we have arrived here, some work has already been done by
1377 // Position::undo_move. In particular, the side to move has been switched,
1378 // so the code below is correct.
1379 Color us = side_to_move();
1380 Color them = opposite_color(us);
1381 Square from = move_from(m);
1382 Square to = move_to(m);
1383 Square capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
1385 assert(to == st->previous->epSquare);
1386 assert(relative_rank(us, to) == RANK_6);
1387 assert(piece_on(to) == piece_of_color_and_type(us, PAWN));
1388 assert(piece_on(from) == EMPTY);
1389 assert(piece_on(capsq) == EMPTY);
1391 // Replace captured piece
1392 set_bit(&(byColorBB[them]), capsq);
1393 set_bit(&(byTypeBB[PAWN]), capsq);
1394 set_bit(&(byTypeBB[0]), capsq);
1395 board[capsq] = piece_of_color_and_type(them, PAWN);
1397 // Remove moving piece from destination square
1398 clear_bit(&(byColorBB[us]), to);
1399 clear_bit(&(byTypeBB[PAWN]), to);
1400 clear_bit(&(byTypeBB[0]), to);
1403 // Replace moving piece at source square
1404 set_bit(&(byColorBB[us]), from);
1405 set_bit(&(byTypeBB[PAWN]), from);
1406 set_bit(&(byTypeBB[0]), from);
1407 board[from] = piece_of_color_and_type(us, PAWN);
1409 // Update piece list:
1410 pieceList[us][PAWN][index[to]] = from;
1411 index[from] = index[to];
1412 pieceList[them][PAWN][pieceCount[them][PAWN]] = capsq;
1413 index[capsq] = pieceCount[them][PAWN];
1415 // Update piece count:
1416 pieceCount[them][PAWN]++;
1420 /// Position::do_null_move makes() a "null move": It switches the side to move
1421 /// and updates the hash key without executing any move on the board.
1423 void Position::do_null_move(StateInfo& backupSt) {
1426 assert(!is_check());
1428 // Back up the information necessary to undo the null move to the supplied
1429 // StateInfo object. In the case of a null move, the only thing we need to
1430 // remember is the last move made and the en passant square.
1431 // Note that differently from normal case here backupSt is actually used as
1432 // a backup storage not as a new state to be used.
1433 backupSt.lastMove = st->lastMove;
1434 backupSt.epSquare = st->epSquare;
1435 backupSt.previous = st->previous;
1436 st->previous = &backupSt;
1438 // Save the current key to the history[] array, in order to be able to
1439 // detect repetition draws.
1440 history[gamePly] = st->key;
1442 // Update the necessary information
1443 sideToMove = opposite_color(sideToMove);
1444 if (st->epSquare != SQ_NONE)
1445 st->key ^= zobEp[st->epSquare];
1447 st->epSquare = SQ_NONE;
1450 st->key ^= zobSideToMove;
1452 st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
1453 st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
1459 /// Position::undo_null_move() unmakes a "null move".
1461 void Position::undo_null_move() {
1464 assert(!is_check());
1466 // Restore information from the our backup StateInfo object
1467 st->lastMove = st->previous->lastMove;
1468 st->epSquare = st->previous->epSquare;
1469 st->previous = st->previous->previous;
1471 if (st->epSquare != SQ_NONE)
1472 st->key ^= zobEp[st->epSquare];
1474 // Update the necessary information
1475 sideToMove = opposite_color(sideToMove);
1478 st->key ^= zobSideToMove;
1480 st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
1481 st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
1487 /// Position::see() is a static exchange evaluator: It tries to estimate the
1488 /// material gain or loss resulting from a move. There are three versions of
1489 /// this function: One which takes a destination square as input, one takes a
1490 /// move, and one which takes a 'from' and a 'to' square. The function does
1491 /// not yet understand promotions captures.
1493 int Position::see(Square to) const {
1495 assert(square_is_ok(to));
1496 return see(SQ_NONE, to);
1499 int Position::see(Move m) const {
1501 assert(move_is_ok(m));
1502 return see(move_from(m), move_to(m));
1505 int Position::see(Square from, Square to) const {
1508 static const int seeValues[18] = {
1509 0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
1510 RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0,
1511 0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
1512 RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0,
1516 Bitboard attackers, occ, b;
1518 assert(square_is_ok(from) || from == SQ_NONE);
1519 assert(square_is_ok(to));
1521 // Initialize colors
1522 Color us = (from != SQ_NONE ? color_of_piece_on(from) : opposite_color(color_of_piece_on(to)));
1523 Color them = opposite_color(us);
1525 // Initialize pieces
1526 Piece piece = piece_on(from);
1527 Piece capture = piece_on(to);
1529 // Find all attackers to the destination square, with the moving piece
1530 // removed, but possibly an X-ray attacker added behind it.
1531 occ = occupied_squares();
1533 // Handle en passant moves
1534 if (st->epSquare == to && type_of_piece_on(from) == PAWN)
1536 assert(capture == EMPTY);
1538 Square capQq = (side_to_move() == WHITE)? (to - DELTA_N) : (to - DELTA_S);
1539 capture = piece_on(capQq);
1541 assert(type_of_piece_on(capQq) == PAWN);
1543 // Remove the captured pawn
1544 clear_bit(&occ, capQq);
1549 clear_bit(&occ, from);
1550 attackers = (rook_attacks_bb(to, occ) & rooks_and_queens())
1551 | (bishop_attacks_bb(to, occ) & bishops_and_queens())
1552 | (piece_attacks<KNIGHT>(to) & knights())
1553 | (piece_attacks<KING>(to) & kings())
1554 | (pawn_attacks(WHITE, to) & pawns(BLACK))
1555 | (pawn_attacks(BLACK, to) & pawns(WHITE));
1557 if (from != SQ_NONE)
1560 // If we don't have any attacker we are finished
1561 if ((attackers & pieces_of_color(us)) == EmptyBoardBB)
1564 // Locate the least valuable attacker to the destination square
1565 // and use it to initialize from square.
1567 for (pt = PAWN; !(attackers & pieces_of_color_and_type(us, pt)); pt++)
1570 from = first_1(attackers & pieces_of_color_and_type(us, pt));
1571 piece = piece_on(from);
1574 // If the opponent has no attackers we are finished
1575 if ((attackers & pieces_of_color(them)) == EmptyBoardBB)
1576 return seeValues[capture];
1578 attackers &= occ; // Remove the moving piece
1580 // The destination square is defended, which makes things rather more
1581 // difficult to compute. We proceed by building up a "swap list" containing
1582 // the material gain or loss at each stop in a sequence of captures to the
1583 // destination square, where the sides alternately capture, and always
1584 // capture with the least valuable piece. After each capture, we look for
1585 // new X-ray attacks from behind the capturing piece.
1586 int lastCapturingPieceValue = seeValues[piece];
1587 int swapList[32], n = 1;
1591 swapList[0] = seeValues[capture];
1594 // Locate the least valuable attacker for the side to move. The loop
1595 // below looks like it is potentially infinite, but it isn't. We know
1596 // that the side to move still has at least one attacker left.
1597 for (pt = PAWN; !(attackers & pieces_of_color_and_type(c, pt)); pt++)
1600 // Remove the attacker we just found from the 'attackers' bitboard,
1601 // and scan for new X-ray attacks behind the attacker.
1602 b = attackers & pieces_of_color_and_type(c, pt);
1603 occ ^= (b & (~b + 1));
1604 attackers |= (rook_attacks_bb(to, occ) & rooks_and_queens())
1605 | (bishop_attacks_bb(to, occ) & bishops_and_queens());
1609 // Add the new entry to the swap list
1611 swapList[n] = -swapList[n - 1] + lastCapturingPieceValue;
1614 // Remember the value of the capturing piece, and change the side to move
1615 // before beginning the next iteration
1616 lastCapturingPieceValue = seeValues[pt];
1617 c = opposite_color(c);
1619 // Stop after a king capture
1620 if (pt == KING && (attackers & pieces_of_color(c)))
1623 swapList[n++] = 100;
1626 } while (attackers & pieces_of_color(c));
1628 // Having built the swap list, we negamax through it to find the best
1629 // achievable score from the point of view of the side to move
1631 swapList[n-1] = Min(-swapList[n], swapList[n-1]);
1637 /// Position::setStartState() copies the content of the argument
1638 /// inside startState and makes st point to it. This is needed
1639 /// when the st pointee could become stale, as example because
1640 /// the caller is about to going out of scope.
1642 void Position::setStartState(const StateInfo& s) {
1649 /// Position::clear() erases the position object to a pristine state, with an
1650 /// empty board, white to move, and no castling rights.
1652 void Position::clear() {
1655 memset(st, 0, sizeof(StateInfo));
1656 st->epSquare = SQ_NONE;
1658 memset(index, 0, sizeof(int) * 64);
1659 memset(byColorBB, 0, sizeof(Bitboard) * 2);
1661 for (int i = 0; i < 64; i++)
1664 for (int i = 0; i < 7; i++)
1666 byTypeBB[i] = EmptyBoardBB;
1667 pieceCount[0][i] = pieceCount[1][i] = 0;
1668 for (int j = 0; j < 8; j++)
1669 pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
1674 initialKFile = FILE_E;
1675 initialKRFile = FILE_H;
1676 initialQRFile = FILE_A;
1680 /// Position::reset_game_ply() simply sets gamePly to 0. It is used from the
1681 /// UCI interface code, whenever a non-reversible move is made in a
1682 /// 'position fen <fen> moves m1 m2 ...' command. This makes it possible
1683 /// for the program to handle games of arbitrary length, as long as the GUI
1684 /// handles draws by the 50 move rule correctly.
1686 void Position::reset_game_ply() {
1692 /// Position::put_piece() puts a piece on the given square of the board,
1693 /// updating the board array, bitboards, and piece counts.
1695 void Position::put_piece(Piece p, Square s) {
1697 Color c = color_of_piece(p);
1698 PieceType pt = type_of_piece(p);
1701 index[s] = pieceCount[c][pt];
1702 pieceList[c][pt][index[s]] = s;
1704 set_bit(&(byTypeBB[pt]), s);
1705 set_bit(&(byColorBB[c]), s);
1706 set_bit(&byTypeBB[0], s); // HACK: byTypeBB[0] contains all occupied squares.
1708 pieceCount[c][pt]++;
1715 /// Position::allow_oo() gives the given side the right to castle kingside.
1716 /// Used when setting castling rights during parsing of FEN strings.
1718 void Position::allow_oo(Color c) {
1720 st->castleRights |= (1 + int(c));
1724 /// Position::allow_ooo() gives the given side the right to castle queenside.
1725 /// Used when setting castling rights during parsing of FEN strings.
1727 void Position::allow_ooo(Color c) {
1729 st->castleRights |= (4 + 4*int(c));
1733 /// Position::compute_key() computes the hash key of the position. The hash
1734 /// key is usually updated incrementally as moves are made and unmade, the
1735 /// compute_key() function is only used when a new position is set up, and
1736 /// to verify the correctness of the hash key when running in debug mode.
1738 Key Position::compute_key() const {
1740 Key result = Key(0ULL);
1742 for (Square s = SQ_A1; s <= SQ_H8; s++)
1743 if (square_is_occupied(s))
1744 result ^= zobrist[color_of_piece_on(s)][type_of_piece_on(s)][s];
1746 if (ep_square() != SQ_NONE)
1747 result ^= zobEp[ep_square()];
1749 result ^= zobCastle[st->castleRights];
1750 if (side_to_move() == BLACK)
1751 result ^= zobSideToMove;
1757 /// Position::compute_pawn_key() computes the hash key of the position. The
1758 /// hash key is usually updated incrementally as moves are made and unmade,
1759 /// the compute_pawn_key() function is only used when a new position is set
1760 /// up, and to verify the correctness of the pawn hash key when running in
1763 Key Position::compute_pawn_key() const {
1765 Key result = Key(0ULL);
1769 for (Color c = WHITE; c <= BLACK; c++)
1774 s = pop_1st_bit(&b);
1775 result ^= zobrist[c][PAWN][s];
1782 /// Position::compute_material_key() computes the hash key of the position.
1783 /// The hash key is usually updated incrementally as moves are made and unmade,
1784 /// the compute_material_key() function is only used when a new position is set
1785 /// up, and to verify the correctness of the material hash key when running in
1788 Key Position::compute_material_key() const {
1790 Key result = Key(0ULL);
1791 for (Color c = WHITE; c <= BLACK; c++)
1792 for (PieceType pt = PAWN; pt <= QUEEN; pt++)
1794 int count = piece_count(c, pt);
1795 for (int i = 0; i <= count; i++)
1796 result ^= zobMaterial[c][pt][i];
1802 /// Position::compute_value() compute the incremental scores for the middle
1803 /// game and the endgame. These functions are used to initialize the incremental
1804 /// scores when a new position is set up, and to verify that the scores are correctly
1805 /// updated by do_move and undo_move when the program is running in debug mode.
1806 template<Position::GamePhase Phase>
1807 Value Position::compute_value() const {
1809 Value result = Value(0);
1813 for (Color c = WHITE; c <= BLACK; c++)
1814 for (PieceType pt = PAWN; pt <= KING; pt++)
1816 b = pieces_of_color_and_type(c, pt);
1819 s = pop_1st_bit(&b);
1820 assert(piece_on(s) == piece_of_color_and_type(c, pt));
1821 result += pst<Phase>(c, pt, s);
1825 const Value TempoValue = (Phase == MidGame ? TempoValueMidgame : TempoValueEndgame);
1826 result += (side_to_move() == WHITE)? TempoValue / 2 : -TempoValue / 2;
1831 /// Position::compute_non_pawn_material() computes the total non-pawn middle
1832 /// game material score for the given side. Material scores are updated
1833 /// incrementally during the search, this function is only used while
1834 /// initializing a new Position object.
1836 Value Position::compute_non_pawn_material(Color c) const {
1838 Value result = Value(0);
1840 for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
1842 Bitboard b = pieces_of_color_and_type(c, pt);
1845 assert(piece_on(first_1(b)) == piece_of_color_and_type(c, pt));
1847 result += piece_value_midgame(pt);
1854 /// Position::is_draw() tests whether the position is drawn by material,
1855 /// repetition, or the 50 moves rule. It does not detect stalemates, this
1856 /// must be done by the search.
1858 bool Position::is_draw() const {
1860 // Draw by material?
1862 && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMidgame))
1865 // Draw by the 50 moves rule?
1866 if (st->rule50 > 100 || (st->rule50 == 100 && !is_check()))
1869 // Draw by repetition?
1870 for (int i = 2; i < Min(gamePly, st->rule50); i += 2)
1871 if (history[gamePly - i] == st->key)
1878 /// Position::is_mate() returns true or false depending on whether the
1879 /// side to move is checkmated.
1881 bool Position::is_mate() const {
1883 MoveStack moves[256];
1885 return is_check() && !generate_evasions(*this, moves, pinned_pieces(sideToMove));
1889 /// Position::has_mate_threat() tests whether a given color has a mate in one
1890 /// from the current position.
1892 bool Position::has_mate_threat(Color c) {
1895 Color stm = side_to_move();
1900 // If the input color is not equal to the side to move, do a null move
1904 MoveStack mlist[120];
1906 bool result = false;
1907 Bitboard dc = discovered_check_candidates(sideToMove);
1908 Bitboard pinned = pinned_pieces(sideToMove);
1910 // Generate pseudo-legal non-capture and capture check moves
1911 count = generate_non_capture_checks(*this, mlist, dc);
1912 count += generate_captures(*this, mlist + count);
1914 // Loop through the moves, and see if one of them is mate
1915 for (int i = 0; i < count; i++)
1917 Move move = mlist[i].move;
1919 if (!pl_move_is_legal(move, pinned))
1929 // Undo null move, if necessary
1937 /// Position::init_zobrist() is a static member function which initializes the
1938 /// various arrays used to compute hash keys.
1940 void Position::init_zobrist() {
1942 for(Piece p = WP; p <= BK; p++)
1943 for(Square s = SQ_A1; s <= SQ_H8; s++)
1944 zobrist[color_of_piece(p)][type_of_piece(p)][s] = genrand_int64();
1947 for(int i = 1; i < 64; i++)
1948 zobEp[i] = genrand_int64();
1950 for(int i = 15; i >= 0; i--)
1951 zobCastle[(i&8) | (i&1) | ((i&2) << 1) | ((i&4) >> 1)] = genrand_int64();
1953 zobSideToMove = genrand_int64();
1955 for (int i = 0; i < 2; i++)
1956 for (int j = 0; j < 8; j++)
1957 for (int k = 0; k < 16; k++)
1958 zobMaterial[i][j][k] = (k > 0)? genrand_int64() : 0LL;
1960 for (int i = 0; i < 16; i++)
1961 zobMaterial[0][KING][i] = zobMaterial[1][KING][i] = 0ULL;
1965 /// Position::init_piece_square_tables() initializes the piece square tables.
1966 /// This is a two-step operation: First, the white halves of the tables are
1967 /// copied from the MgPST[][] and EgPST[][] arrays, with a small random number
1968 /// added to each entry if the "Randomness" UCI parameter is non-zero.
1969 /// Second, the black halves of the tables are initialized by mirroring
1970 /// and changing the sign of the corresponding white scores.
1972 void Position::init_piece_square_tables() {
1974 int r = get_option_value_int("Randomness"), i;
1975 for (Square s = SQ_A1; s <= SQ_H8; s++)
1976 for (Piece p = WP; p <= WK; p++)
1978 i = (r == 0)? 0 : (genrand_int32() % (r*2) - r);
1979 MgPieceSquareTable[p][s] = Value(MgPST[p][s] + i);
1980 EgPieceSquareTable[p][s] = Value(EgPST[p][s] + i);
1983 for (Square s = SQ_A1; s <= SQ_H8; s++)
1984 for (Piece p = BP; p <= BK; p++)
1986 MgPieceSquareTable[p][s] = -MgPieceSquareTable[p-8][flip_square(s)];
1987 EgPieceSquareTable[p][s] = -EgPieceSquareTable[p-8][flip_square(s)];
1992 /// Position::flipped_copy() makes a copy of the input position, but with
1993 /// the white and black sides reversed. This is only useful for debugging,
1994 /// especially for finding evaluation symmetry bugs.
1996 void Position::flipped_copy(const Position &pos) {
1998 assert(pos.is_ok());
2003 for (Square s = SQ_A1; s <= SQ_H8; s++)
2004 if (!pos.square_is_empty(s))
2005 put_piece(Piece(int(pos.piece_on(s)) ^ 8), flip_square(s));
2008 sideToMove = opposite_color(pos.side_to_move());
2011 if (pos.can_castle_kingside(WHITE)) allow_oo(BLACK);
2012 if (pos.can_castle_queenside(WHITE)) allow_ooo(BLACK);
2013 if (pos.can_castle_kingside(BLACK)) allow_oo(WHITE);
2014 if (pos.can_castle_queenside(BLACK)) allow_ooo(WHITE);
2016 initialKFile = pos.initialKFile;
2017 initialKRFile = pos.initialKRFile;
2018 initialQRFile = pos.initialQRFile;
2020 for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
2021 castleRightsMask[sq] = ALL_CASTLES;
2023 castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO | WHITE_OOO);
2024 castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO | BLACK_OOO);
2025 castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO;
2026 castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO;
2027 castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO;
2028 castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO;
2030 // En passant square
2031 if (pos.st->epSquare != SQ_NONE)
2032 st->epSquare = flip_square(pos.st->epSquare);
2038 st->key = compute_key();
2039 st->pawnKey = compute_pawn_key();
2040 st->materialKey = compute_material_key();
2042 // Incremental scores
2043 st->mgValue = compute_value<MidGame>();
2044 st->egValue = compute_value<EndGame>();
2047 npMaterial[WHITE] = compute_non_pawn_material(WHITE);
2048 npMaterial[BLACK] = compute_non_pawn_material(BLACK);
2054 /// Position::is_ok() performs some consitency checks for the position object.
2055 /// This is meant to be helpful when debugging.
2057 bool Position::is_ok(int* failedStep) const {
2059 // What features of the position should be verified?
2060 static const bool debugBitboards = false;
2061 static const bool debugKingCount = false;
2062 static const bool debugKingCapture = false;
2063 static const bool debugCheckerCount = false;
2064 static const bool debugKey = false;
2065 static const bool debugMaterialKey = false;
2066 static const bool debugPawnKey = false;
2067 static const bool debugIncrementalEval = false;
2068 static const bool debugNonPawnMaterial = false;
2069 static const bool debugPieceCounts = false;
2070 static const bool debugPieceList = false;
2072 if (failedStep) *failedStep = 1;
2075 if (!color_is_ok(side_to_move()))
2078 // Are the king squares in the position correct?
2079 if (failedStep) (*failedStep)++;
2080 if (piece_on(king_square(WHITE)) != WK)
2083 if (failedStep) (*failedStep)++;
2084 if (piece_on(king_square(BLACK)) != BK)
2088 if (failedStep) (*failedStep)++;
2089 if (!file_is_ok(initialKRFile))
2092 if (!file_is_ok(initialQRFile))
2095 // Do both sides have exactly one king?
2096 if (failedStep) (*failedStep)++;
2099 int kingCount[2] = {0, 0};
2100 for (Square s = SQ_A1; s <= SQ_H8; s++)
2101 if (type_of_piece_on(s) == KING)
2102 kingCount[color_of_piece_on(s)]++;
2104 if (kingCount[0] != 1 || kingCount[1] != 1)
2108 // Can the side to move capture the opponent's king?
2109 if (failedStep) (*failedStep)++;
2110 if (debugKingCapture)
2112 Color us = side_to_move();
2113 Color them = opposite_color(us);
2114 Square ksq = king_square(them);
2115 if (square_is_attacked(ksq, us))
2119 // Is there more than 2 checkers?
2120 if (failedStep) (*failedStep)++;
2121 if (debugCheckerCount && count_1s(st->checkersBB) > 2)
2125 if (failedStep) (*failedStep)++;
2128 // The intersection of the white and black pieces must be empty
2129 if ((pieces_of_color(WHITE) & pieces_of_color(BLACK)) != EmptyBoardBB)
2132 // The union of the white and black pieces must be equal to all
2134 if ((pieces_of_color(WHITE) | pieces_of_color(BLACK)) != occupied_squares())
2137 // Separate piece type bitboards must have empty intersections
2138 for (PieceType p1 = PAWN; p1 <= KING; p1++)
2139 for (PieceType p2 = PAWN; p2 <= KING; p2++)
2140 if (p1 != p2 && (pieces_of_type(p1) & pieces_of_type(p2)))
2144 // En passant square OK?
2145 if (failedStep) (*failedStep)++;
2146 if (ep_square() != SQ_NONE)
2148 // The en passant square must be on rank 6, from the point of view of the
2150 if (relative_rank(side_to_move(), ep_square()) != RANK_6)
2155 if (failedStep) (*failedStep)++;
2156 if (debugKey && st->key != compute_key())
2159 // Pawn hash key OK?
2160 if (failedStep) (*failedStep)++;
2161 if (debugPawnKey && st->pawnKey != compute_pawn_key())
2164 // Material hash key OK?
2165 if (failedStep) (*failedStep)++;
2166 if (debugMaterialKey && st->materialKey != compute_material_key())
2169 // Incremental eval OK?
2170 if (failedStep) (*failedStep)++;
2171 if (debugIncrementalEval)
2173 if (st->mgValue != compute_value<MidGame>())
2176 if (st->egValue != compute_value<EndGame>())
2180 // Non-pawn material OK?
2181 if (failedStep) (*failedStep)++;
2182 if (debugNonPawnMaterial)
2184 if (npMaterial[WHITE] != compute_non_pawn_material(WHITE))
2187 if (npMaterial[BLACK] != compute_non_pawn_material(BLACK))
2192 if (failedStep) (*failedStep)++;
2193 if (debugPieceCounts)
2194 for (Color c = WHITE; c <= BLACK; c++)
2195 for (PieceType pt = PAWN; pt <= KING; pt++)
2196 if (pieceCount[c][pt] != count_1s(pieces_of_color_and_type(c, pt)))
2199 if (failedStep) (*failedStep)++;
2202 for(Color c = WHITE; c <= BLACK; c++)
2203 for(PieceType pt = PAWN; pt <= KING; pt++)
2204 for(int i = 0; i < pieceCount[c][pt]; i++)
2206 if (piece_on(piece_list(c, pt, i)) != piece_of_color_and_type(c, pt))
2209 if (index[piece_list(c, pt, i)] != i)
2213 if (failedStep) *failedStep = 0;