X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fposition.cpp;h=14490cdd4729c6a55632e3d3ac861509b779679d;hp=69a756d9ce9b0b68ab0eecce7758a4ced1e05401;hb=3f44f5303bb0f3c9c02385ea25f32c14dedfd09b;hpb=e06a117d5e78ec4edc051f2b161d36559f784d37 diff --git a/src/position.cpp b/src/position.cpp index 69a756d9..14490cdd 100644 --- a/src/position.cpp +++ b/src/position.cpp @@ -52,6 +52,9 @@ namespace { const string PieceToChar(" PNBRQK pnbrqk"); +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. @@ -62,7 +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); @@ -269,7 +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); @@ -378,8 +381,7 @@ 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 is not playable, -/// indeed is even not guaranteed to be legal. +/// get the material key out of an endgame code. Position& Position::set(const string& code, Color c, StateInfo* si) { @@ -391,8 +393,8 @@ Position& Position::set(const string& code, Color c, StateInfo* si) { std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower); - string fenStr = sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/8/8/" - + sides[1] + char(8 - sides[1].length() + '0') + " w - - 0 10"; + 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); } @@ -448,19 +450,6 @@ 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 @@ -474,7 +463,7 @@ Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners pinners = 0; // Snipers are sliders that attack 's' when a piece is removed - Bitboard snipers = ( (PseudoAttacks[ROOK ][s] & pieces(QUEEN, ROOK)) + Bitboard snipers = ( (PseudoAttacks[ ROOK][s] & pieces(QUEEN, ROOK)) | (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders; while (snipers) @@ -501,7 +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)); } @@ -688,7 +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 @@ -997,18 +986,16 @@ Key Position::key_after(Move m) const { /// Position::see_ge (Static Exchange Evaluation Greater or Equal) tests if the -/// SEE value of move is greater or equal to the given value. We'll use an +/// 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. -bool Position::see_ge(Move m, Value v) const { +bool Position::see_ge(Move m, Value threshold) const { assert(is_ok(m)); - // Castling moves are implemented as king capturing the rook so cannot be - // handled correctly. Simply assume the SEE value is 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 >= v; + // Only deal with normal moves, assume others pass a simple see + if (type_of(m) != NORMAL) + return VALUE_ZERO >= threshold; Square from = from_sq(m), to = to_sq(m); PieceType nextVictim = type_of(piece_on(from)); @@ -1016,30 +1003,22 @@ bool Position::see_ge(Move m, Value v) const { Value balance; // Values of the pieces taken by us minus opponent's ones Bitboard occupied, stmAttackers; - if (type_of(m) == ENPASSANT) - { - occupied = SquareBB[to - pawn_push(~stm)]; // Remove the captured pawn - balance = PieceValue[MG][PAWN]; - } - else - { - balance = PieceValue[MG][piece_on(to)]; - occupied = 0; - } + // The opponent may be able to recapture so this is the best result + // we can hope for. + balance = PieceValue[MG][piece_on(to)] - threshold; - if (balance < v) + if (balance < VALUE_ZERO) return false; - if (nextVictim == KING) - return true; - + // Now assume the worst possible result: that the opponent can + // capture our piece for free. balance -= PieceValue[MG][nextVictim]; - if (balance >= v) + if (balance >= VALUE_ZERO) // Always true if nextVictim == KING return true; - bool relativeStm = true; // True if the opponent is to move - occupied ^= pieces() ^ from ^ to; + bool opponentToMove = true; + occupied = pieces() ^ from ^ to; // Find all attackers to the destination square, with the moving piece removed, // but possibly an X-ray attacker added behind it. @@ -1047,6 +1026,12 @@ bool Position::see_ge(Move m, Value v) const { while (true) { + // 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); + stmAttackers = attackers & pieces(stm); // Don't allow pinned pieces to attack pieces except the king as long all @@ -1054,25 +1039,40 @@ bool Position::see_ge(Move m, Value v) const { if (!(st->pinnersForKing[stm] & ~occupied)) stmAttackers &= ~st->blockersForKing[stm]; + // If we have no more attackers we must give up if (!stmAttackers) - return relativeStm; + break; // Locate and remove the next least valuable attacker nextVictim = min_attacker(byTypeBB, to, stmAttackers, occupied, attackers); if (nextVictim == KING) - return relativeStm == bool(attackers & pieces(~stm)); - - balance += relativeStm ? PieceValue[MG][nextVictim] - : -PieceValue[MG][nextVictim]; + { + // 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; + } - relativeStm = !relativeStm; + // Assume the opponent can win the next piece for free and switch sides + balance += PieceValue[MG][nextVictim]; + opponentToMove = !opponentToMove; - if (relativeStm == (balance >= v)) - return relativeStm; + // If balance is negative after receiving a free piece then give up + if (balance < VALUE_ZERO) + break; + // 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; } + + // If the opponent gave up we win, otherwise we lose. + return opponentToMove; } @@ -1096,11 +1096,10 @@ bool Position::is_draw(int ply) const { { stp = stp->previous->previous; - // At root position ply is 1, so return a draw score if a position - // repeats once earlier but after or at the root, or repeats twice - // strictly before the root. + // 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 > 0) == 2) + && ++cnt + (ply > i) == 2) return true; } @@ -1143,78 +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; }