X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fposition.cpp;h=14490cdd4729c6a55632e3d3ac861509b779679d;hp=e51c1ba70296a7149460da078c1032b1582a3b88;hb=3f44f5303bb0f3c9c02385ea25f32c14dedfd09b;hpb=90ce24b11ea080f923e1b5d37470e2ca98f4d98b diff --git a/src/position.cpp b/src/position.cpp index e51c1ba7..14490cdd 100644 --- a/src/position.cpp +++ b/src/position.cpp @@ -2,7 +2,7 @@ Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad - Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -20,7 +20,8 @@ #include #include -#include // For std::memset, std::memcmp +#include // For offsetof() +#include // For std::memset, std::memcmp #include #include @@ -31,22 +32,30 @@ #include "thread.h" #include "tt.h" #include "uci.h" +#include "syzygy/tbprobe.h" using std::string; +namespace PSQT { + extern Score psq[PIECE_NB][SQUARE_NB]; +} + namespace Zobrist { Key psq[PIECE_NB][SQUARE_NB]; Key enpassant[FILE_NB]; Key castling[CASTLING_RIGHT_NB]; - Key side; + Key side, noPawns; } namespace { const string PieceToChar(" PNBRQK pnbrqk"); -// min_attacker() is a helper function used by see() to locate the least +const Piece Pieces[] = { W_PAWN, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING, + B_PAWN, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING }; + +// min_attacker() is a helper function used by see_ge() to locate the least // valuable attacker for the side to move, remove the attacker we just found // from the bitboards and scan for new X-ray attacks behind it. @@ -56,7 +65,7 @@ PieceType min_attacker(const Bitboard* bb, Square to, Bitboard stmAttackers, Bitboard b = stmAttackers & bb[Pt]; if (!b) - return min_attacker(bb, to, stmAttackers, occupied, attackers); + return min_attacker(bb, to, stmAttackers, occupied, attackers); occupied ^= b & ~(b - 1); @@ -93,11 +102,25 @@ std::ostream& operator<<(std::ostream& os, const Position& pos) { } os << "\nFen: " << pos.fen() << "\nKey: " << std::hex << std::uppercase - << std::setfill('0') << std::setw(16) << pos.key() << std::dec << "\nCheckers: "; + << std::setfill('0') << std::setw(16) << pos.key() + << std::setfill(' ') << std::dec << "\nCheckers: "; for (Bitboard b = pos.checkers(); b; ) os << UCI::square(pop_lsb(&b)) << " "; + if ( int(Tablebases::MaxCardinality) >= popcount(pos.pieces()) + && !pos.can_castle(ANY_CASTLING)) + { + StateInfo st; + Position p; + p.set(pos.fen(), pos.is_chess960(), &st, pos.this_thread()); + Tablebases::ProbeState s1, s2; + Tablebases::WDLScore wdl = Tablebases::probe_wdl(p, &s1); + int dtz = Tablebases::probe_dtz(p, &s2); + os << "\nTablebases WDL: " << std::setw(4) << wdl << " (" << s1 << ")" + << "\nTablebases DTZ: " << std::setw(4) << dtz << " (" << s2 << ")"; + } + return os; } @@ -128,6 +151,7 @@ void Position::init() { } Zobrist::side = rng.rand(); + Zobrist::noPawns = rng.rand(); } @@ -159,8 +183,9 @@ Position& Position::set(const string& fenStr, bool isChess960, StateInfo* si, Th 4) En passant target square (in algebraic notation). If there's no en passant target square, this is "-". If a pawn has just made a 2-square move, this - is the position "behind" the pawn. This is recorded regardless of whether - there is a pawn in position to make an en passant capture. + is the position "behind" the pawn. This is recorded only if there is a pawn + in position to make an en passant capture, and if there really is a pawn + that might have advanced two squares. 5) Halfmove clock. This is the number of halfmoves since the last pawn advance or capture. This is used to determine if a draw can be claimed under the @@ -237,7 +262,8 @@ Position& Position::set(const string& fenStr, bool isChess960, StateInfo* si, Th { st->epSquare = make_square(File(col - 'a'), Rank(row - '1')); - if (!(attackers_to(st->epSquare) & pieces(sideToMove, PAWN))) + if ( !(attackers_to(st->epSquare) & pieces(sideToMove, PAWN)) + || !(pieces(~sideToMove, PAWN) & (st->epSquare + pawn_push(~sideToMove)))) st->epSquare = SQ_NONE; } else @@ -246,7 +272,7 @@ Position& Position::set(const string& fenStr, bool isChess960, StateInfo* si, Th // 5-6. Halfmove clock and fullmove number ss >> std::skipws >> st->rule50 >> gamePly; - // Convert from fullmove starting from 1 to ply starting from 0, + // Convert from fullmove starting from 1 to gamePly starting from 0, // handle also common incorrect FEN with fullmove = 0. gamePly = std::max(2 * (gamePly - 1), 0) + (sideToMove == BLACK); @@ -312,7 +338,8 @@ void Position::set_check_info(StateInfo* si) const { void Position::set_state(StateInfo* si) const { - si->key = si->pawnKey = si->materialKey = 0; + si->key = si->materialKey = 0; + si->pawnKey = Zobrist::noPawns; si->nonPawnMaterial[WHITE] = si->nonPawnMaterial[BLACK] = VALUE_ZERO; si->psq = SCORE_ZERO; si->checkersBB = attackers_to(square(sideToMove)) & pieces(~sideToMove); @@ -352,6 +379,27 @@ void Position::set_state(StateInfo* si) const { } +/// Position::set() is an overload to initialize the position object with +/// the given endgame code string like "KBPKN". It is mainly a helper to +/// get the material key out of an endgame code. + +Position& Position::set(const string& code, Color c, StateInfo* si) { + + assert(code.length() > 0 && code.length() < 8); + assert(code[0] == 'K'); + + string sides[] = { code.substr(code.find('K', 1)), // Weak + code.substr(0, code.find('K', 1)) }; // Strong + + std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower); + + string fenStr = "8/" + sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/" + + sides[1] + char(8 - sides[1].length() + '0') + "/8 w - - 0 10"; + + return set(fenStr, false, si, nullptr); +} + + /// Position::fen() returns a FEN representation of the position. In case of /// Chess960 the Shredder-FEN notation is used. This is mainly a debugging function. @@ -402,41 +450,33 @@ const string Position::fen() const { } -/// Position::game_phase() calculates the game phase interpolating total non-pawn -/// material between endgame and midgame limits. - -Phase Position::game_phase() const { - - Value npm = st->nonPawnMaterial[WHITE] + st->nonPawnMaterial[BLACK]; - - npm = std::max(EndgameLimit, std::min(npm, MidgameLimit)); - - return Phase(((npm - EndgameLimit) * PHASE_MIDGAME) / (MidgameLimit - EndgameLimit)); -} - - /// Position::slider_blockers() returns a bitboard of all the pieces (both colors) /// that are blocking attacks on the square 's' from 'sliders'. A piece blocks a /// slider if removing that piece from the board would result in a position where /// square 's' is attacked. For example, a king-attack blocking piece can be either /// a pinned or a discovered check piece, according if its color is the opposite -/// or the same of the color of the slider. The pinners bitboard get filled with -/// real and potential pinners. +/// or the same of the color of the slider. Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const { - Bitboard b, p, result = 0; + Bitboard result = 0; + pinners = 0; - // Pinners are sliders that attack 's' when a pinned piece is removed - pinners = p = ( (PseudoAttacks[ROOK ][s] & pieces(QUEEN, ROOK)) - | (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders; + // Snipers are sliders that attack 's' when a piece is removed + Bitboard snipers = ( (PseudoAttacks[ ROOK][s] & pieces(QUEEN, ROOK)) + | (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders; - while (p) + while (snipers) { - b = between_bb(s, pop_lsb(&p)) & pieces(); - - if (!more_than_one(b)) - result |= b; + Square sniperSq = pop_lsb(&snipers); + Bitboard b = between_bb(s, sniperSq) & pieces(); + + if (!more_than_one(b)) + { + result |= b; + if (b & pieces(color_of(piece_on(s)))) + pinners |= sniperSq; + } } return result; } @@ -450,7 +490,7 @@ Bitboard Position::attackers_to(Square s, Bitboard occupied) const { return (attacks_from(s, BLACK) & pieces(WHITE, PAWN)) | (attacks_from(s, WHITE) & pieces(BLACK, PAWN)) | (attacks_from(s) & pieces(KNIGHT)) - | (attacks_bb(s, occupied) & pieces(ROOK, QUEEN)) + | (attacks_bb< ROOK>(s, occupied) & pieces( ROOK, QUEEN)) | (attacks_bb(s, occupied) & pieces(BISHOP, QUEEN)) | (attacks_from(s) & pieces(KING)); } @@ -544,7 +584,7 @@ bool Position::pseudo_legal(const Move m) const { && empty(to - pawn_push(us)))) return false; } - else if (!(attacks_from(pc, from) & to)) + else if (!(attacks_from(type_of(pc), from) & to)) return false; // Evasions generator already takes care to avoid some kind of illegal moves @@ -597,7 +637,7 @@ bool Position::gives_check(Move m) const { return false; case PROMOTION: - return attacks_bb(Piece(promotion_type(m)), to, pieces() ^ from) & square(~sideToMove); + return attacks_bb(promotion_type(m), to, pieces() ^ from) & square(~sideToMove); // En passant capture with check? We have already handled the case // of direct checks and ordinary discovered check, so the only case we @@ -637,7 +677,7 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) { assert(is_ok(m)); assert(&newSt != st); - ++nodes; + thisThread->nodes.fetch_add(1, std::memory_order_relaxed); Key k = st->key ^ Zobrist::side; // Copy some fields of the old state to our new StateInfo object except the @@ -776,7 +816,7 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) { // Update pawn hash key and prefetch access to pawnsTable st->pawnKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to]; - prefetch(thisThread->pawnsTable[st->pawnKey]); + prefetch2(thisThread->pawnsTable[st->pawnKey]); // Reset rule 50 draw counter st->rule50 = 0; @@ -945,124 +985,122 @@ Key Position::key_after(Move m) const { } -/// Position::see() is a static exchange evaluator: It tries to estimate the -/// material gain or loss resulting from a move. +/// Position::see_ge (Static Exchange Evaluation Greater or Equal) tests if the +/// SEE value of move is greater or equal to the given threshold. We'll use an +/// algorithm similar to alpha-beta pruning with a null window. -Value Position::see_sign(Move m) const { +bool Position::see_ge(Move m, Value threshold) const { assert(is_ok(m)); - // Early return if SEE cannot be negative because captured piece value - // is not less then capturing one. Note that king moves always return - // here because king midgame value is set to 0. - if (PieceValue[MG][moved_piece(m)] <= PieceValue[MG][piece_on(to_sq(m))]) - return VALUE_KNOWN_WIN; + // Only deal with normal moves, assume others pass a simple see + if (type_of(m) != NORMAL) + return VALUE_ZERO >= threshold; - return see(m); -} + Square from = from_sq(m), to = to_sq(m); + PieceType nextVictim = type_of(piece_on(from)); + Color stm = ~color_of(piece_on(from)); // First consider opponent's move + Value balance; // Values of the pieces taken by us minus opponent's ones + Bitboard occupied, stmAttackers; -Value Position::see(Move m) const { + // The opponent may be able to recapture so this is the best result + // we can hope for. + balance = PieceValue[MG][piece_on(to)] - threshold; - Square from, to; - Bitboard occupied, attackers, stmAttackers; - Value swapList[32]; - int slIndex = 1; - PieceType captured; - Color stm; + if (balance < VALUE_ZERO) + return false; - assert(is_ok(m)); + // Now assume the worst possible result: that the opponent can + // capture our piece for free. + balance -= PieceValue[MG][nextVictim]; - from = from_sq(m); - to = to_sq(m); - swapList[0] = PieceValue[MG][piece_on(to)]; - stm = color_of(piece_on(from)); - occupied = pieces() ^ from; + if (balance >= VALUE_ZERO) // Always true if nextVictim == KING + return true; - // Castling moves are implemented as king capturing the rook so cannot - // be handled correctly. Simply return VALUE_ZERO that is always correct - // unless in the rare case the rook ends up under attack. - if (type_of(m) == CASTLING) - return VALUE_ZERO; + bool opponentToMove = true; + occupied = pieces() ^ from ^ to; - if (type_of(m) == ENPASSANT) - { - occupied ^= to - pawn_push(stm); // Remove the captured pawn - swapList[0] = PieceValue[MG][PAWN]; - } + // Find all attackers to the destination square, with the moving piece removed, + // but possibly an X-ray attacker added behind it. + Bitboard attackers = attackers_to(to, occupied) & occupied; - // Find all attackers to the destination square, with the moving piece - // removed, but possibly an X-ray attacker added behind it. - attackers = attackers_to(to, occupied) & occupied; - - // If the opponent has no attackers we are finished - stm = ~stm; - stmAttackers = attackers & pieces(stm); - if (!stmAttackers) - return swapList[0]; - - // Don't allow pinned pieces to attack as long all pinners (this includes also - // potential ones) are on their original square. When a pinner moves to the - // exchange-square or get captured on it, we fall back to standard SEE behaviour. - else if ( (stmAttackers & st->blockersForKing[stm]) - && ((st->pinnersForKing[stm] & (occupied ^ (occupied & to))) == st->pinnersForKing[stm])) + while (true) { - // Pinned pieces can't attack so remove them from attackers - stmAttackers ^= (stmAttackers & st->blockersForKing[stm]); - if (!stmAttackers) - return swapList[0]; - } + // The balance is negative only because we assumed we could win + // the last piece for free. We are truly winning only if we can + // win the last piece _cheaply enough_. Test if we can actually + // do this otherwise "give up". + assert(balance < VALUE_ZERO); - // The destination square is defended, which makes things rather more - // difficult to compute. We proceed by building up a "swap list" containing - // the material gain or loss at each stop in a sequence of captures to the - // destination square, where the sides alternately capture, and always - // capture with the least valuable piece. After each capture, we look for - // new X-ray attacks from behind the capturing piece. - captured = type_of(piece_on(from)); + stmAttackers = attackers & pieces(stm); - do { - assert(slIndex < 32); + // Don't allow pinned pieces to attack pieces except the king as long all + // pinners are on their original square. + if (!(st->pinnersForKing[stm] & ~occupied)) + stmAttackers &= ~st->blockersForKing[stm]; - // Add the new entry to the swap list - swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured]; + // If we have no more attackers we must give up + if (!stmAttackers) + break; // Locate and remove the next least valuable attacker - captured = min_attacker(byTypeBB, to, stmAttackers, occupied, attackers); - stm = ~stm; - stmAttackers = attackers & pieces(stm); - if ( stmAttackers - && (stmAttackers & st->blockersForKing[stm]) - && ((st->pinnersForKing[stm] & (occupied ^ (occupied & to))) == st->pinnersForKing[stm])) - stmAttackers ^= (stmAttackers & st->blockersForKing[stm]); + nextVictim = min_attacker(byTypeBB, to, stmAttackers, occupied, attackers); + + if (nextVictim == KING) + { + // Our only attacker is the king. If the opponent still has + // attackers we must give up. Otherwise we make the move and + // (having no more attackers) the opponent must give up. + if (!(attackers & pieces(~stm))) + opponentToMove = !opponentToMove; + break; + } - ++slIndex; + // Assume the opponent can win the next piece for free and switch sides + balance += PieceValue[MG][nextVictim]; + opponentToMove = !opponentToMove; - } while (stmAttackers && (captured != KING || (--slIndex, false))); // Stop before a king capture + // If balance is negative after receiving a free piece then give up + if (balance < VALUE_ZERO) + break; - // Having built the swap list, we negamax through it to find the best - // achievable score from the point of view of the side to move. - while (--slIndex) - swapList[slIndex - 1] = std::min(-swapList[slIndex], swapList[slIndex - 1]); + // Complete the process of switching sides. The first line swaps + // all negative numbers with non-negative numbers. The compiler + // probably knows that it is just the bitwise negation ~balance. + balance = -balance-1; + stm = ~stm; + } - return swapList[0]; + // If the opponent gave up we win, otherwise we lose. + return opponentToMove; } /// Position::is_draw() tests whether the position is drawn by 50-move rule /// or by repetition. It does not detect stalemates. -bool Position::is_draw() const { +bool Position::is_draw(int ply) const { if (st->rule50 > 99 && (!checkers() || MoveList(*this).size())) return true; - StateInfo* stp = st; - for (int i = 2, e = std::min(st->rule50, st->pliesFromNull); i <= e; i += 2) + int end = std::min(st->rule50, st->pliesFromNull); + + if (end < 4) + return false; + + StateInfo* stp = st->previous->previous; + int cnt = 0; + + for (int i = 4; i <= end; i += 2) { stp = stp->previous->previous; - if (stp->key == st->key) - return true; // Draw at first repetition + // Return a draw score if a position repeats once earlier but strictly + // after the root, or repeats twice before or at the root. + if ( stp->key == st->key + && ++cnt + (ply > i) == 2) + return true; } return false; @@ -1104,78 +1142,72 @@ void Position::flip() { } -/// Position::pos_is_ok() performs some consistency checks for the position object. +/// Position::pos_is_ok() performs some consistency checks for the +/// position object and raises an asserts if something wrong is detected. /// This is meant to be helpful when debugging. -bool Position::pos_is_ok(int* failedStep) const { +bool Position::pos_is_ok() const { const bool Fast = true; // Quick (default) or full check? - enum { Default, King, Bitboards, State, Lists, Castling }; + if ( (sideToMove != WHITE && sideToMove != BLACK) + || piece_on(square(WHITE)) != W_KING + || piece_on(square(BLACK)) != B_KING + || ( ep_square() != SQ_NONE + && relative_rank(sideToMove, ep_square()) != RANK_6)) + assert(0 && "pos_is_ok: Default"); - for (int step = Default; step <= (Fast ? Default : Castling); step++) - { - if (failedStep) - *failedStep = step; - - if (step == Default) - if ( (sideToMove != WHITE && sideToMove != BLACK) - || piece_on(square(WHITE)) != W_KING - || piece_on(square(BLACK)) != B_KING - || ( ep_square() != SQ_NONE - && relative_rank(sideToMove, ep_square()) != RANK_6)) - return false; + if (Fast) + return true; - if (step == King) - if ( std::count(board, board + SQUARE_NB, W_KING) != 1 - || std::count(board, board + SQUARE_NB, B_KING) != 1 - || attackers_to(square(~sideToMove)) & pieces(sideToMove)) - return false; + if ( pieceCount[W_KING] != 1 + || pieceCount[B_KING] != 1 + || attackers_to(square(~sideToMove)) & pieces(sideToMove)) + assert(0 && "pos_is_ok: Kings"); - if (step == Bitboards) - { - if ( (pieces(WHITE) & pieces(BLACK)) - ||(pieces(WHITE) | pieces(BLACK)) != pieces()) - return false; + if ( (pieces(PAWN) & (Rank1BB | Rank8BB)) + || pieceCount[W_PAWN] > 8 + || pieceCount[B_PAWN] > 8) + assert(0 && "pos_is_ok: Pawns"); - for (PieceType p1 = PAWN; p1 <= KING; ++p1) - for (PieceType p2 = PAWN; p2 <= KING; ++p2) - if (p1 != p2 && (pieces(p1) & pieces(p2))) - return false; - } + if ( (pieces(WHITE) & pieces(BLACK)) + || (pieces(WHITE) | pieces(BLACK)) != pieces() + || popcount(pieces(WHITE)) > 16 + || popcount(pieces(BLACK)) > 16) + assert(0 && "pos_is_ok: Bitboards"); - if (step == State) - { - StateInfo si = *st; - set_state(&si); - if (std::memcmp(&si, st, sizeof(StateInfo))) - return false; - } + for (PieceType p1 = PAWN; p1 <= KING; ++p1) + for (PieceType p2 = PAWN; p2 <= KING; ++p2) + if (p1 != p2 && (pieces(p1) & pieces(p2))) + assert(0 && "pos_is_ok: Bitboards"); - if (step == Lists) - for (Piece pc : Pieces) - { - if (pieceCount[pc] != popcount(pieces(color_of(pc), type_of(pc)))) - return false; + StateInfo si = *st; + set_state(&si); + if (std::memcmp(&si, st, sizeof(StateInfo))) + assert(0 && "pos_is_ok: State"); - for (int i = 0; i < pieceCount[pc]; ++i) - if (board[pieceList[pc][i]] != pc || index[pieceList[pc][i]] != i) - return false; - } + for (Piece pc : Pieces) + { + if ( pieceCount[pc] != popcount(pieces(color_of(pc), type_of(pc))) + || pieceCount[pc] != std::count(board, board + SQUARE_NB, pc)) + assert(0 && "pos_is_ok: Pieces"); - if (step == Castling) - for (Color c = WHITE; c <= BLACK; ++c) - for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1)) - { - if (!can_castle(c | s)) - continue; - - if ( piece_on(castlingRookSquare[c | s]) != make_piece(c, ROOK) - || castlingRightsMask[castlingRookSquare[c | s]] != (c | s) - ||(castlingRightsMask[square(c)] & (c | s)) != (c | s)) - return false; - } + for (int i = 0; i < pieceCount[pc]; ++i) + if (board[pieceList[pc][i]] != pc || index[pieceList[pc][i]] != i) + assert(0 && "pos_is_ok: Index"); } + for (Color c = WHITE; c <= BLACK; ++c) + for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1)) + { + if (!can_castle(c | s)) + continue; + + if ( piece_on(castlingRookSquare[c | s]) != make_piece(c, ROOK) + || castlingRightsMask[castlingRookSquare[c | s]] != (c | s) + || (castlingRightsMask[square(c)] & (c | s)) != (c | s)) + assert(0 && "pos_is_ok: Castling"); + } + return true; }