X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fposition.cpp;h=0be309ee60cac3d0ea78bcec0ad6c38237e7768b;hp=aa06db08c106ae9f5c1689e2e3b110671f21a25c;hb=255df4ffae29f4a038c9881c1f2f675e2f21f71e;hpb=13b4444d9e3a3ac5a71f256145904d13754f9e7f diff --git a/src/position.cpp b/src/position.cpp index aa06db08..0be309ee 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) 2015-2018 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 @@ -31,42 +32,55 @@ #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[COLOR_NB][PIECE_TYPE_NB][SQUARE_NB]; + 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 +constexpr 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. template -PieceType min_attacker(const Bitboard* bb, Square to, Bitboard stmAttackers, +PieceType min_attacker(const Bitboard* byTypeBB, Square to, Bitboard stmAttackers, Bitboard& occupied, Bitboard& attackers) { - Bitboard b = stmAttackers & bb[Pt]; + Bitboard b = stmAttackers & byTypeBB[Pt]; if (!b) - return min_attacker(bb, to, stmAttackers, occupied, attackers); + return min_attacker(byTypeBB, to, stmAttackers, occupied, attackers); - occupied ^= b & ~(b - 1); + occupied ^= lsb(b); // Remove the attacker from occupied + // Add any X-ray attack behind the just removed piece. For instance with + // rooks in a8 and a7 attacking a1, after removing a7 we add rook in a8. + // Note that new added attackers can be of any color. if (Pt == PAWN || Pt == BISHOP || Pt == QUEEN) - attackers |= attacks_bb(to, occupied) & (bb[BISHOP] | bb[QUEEN]); + attackers |= attacks_bb(to, occupied) & (byTypeBB[BISHOP] | byTypeBB[QUEEN]); if (Pt == ROOK || Pt == QUEEN) - attackers |= attacks_bb(to, occupied) & (bb[ROOK] | bb[QUEEN]); + attackers |= attacks_bb(to, occupied) & (byTypeBB[ROOK] | byTypeBB[QUEEN]); - attackers &= occupied; // After X-ray that may add already processed pieces + // X-ray may add already processed pieces because byTypeBB[] is constant: in + // the rook example, now attackers contains _again_ rook in a7, so remove it. + attackers &= occupied; return (PieceType)Pt; } @@ -93,11 +107,25 @@ 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; } @@ -109,10 +137,9 @@ void Position::init() { PRNG rng(1070372); - for (Color c = WHITE; c <= BLACK; ++c) - for (PieceType pt = PAWN; pt <= KING; ++pt) - for (Square s = SQ_A1; s <= SQ_H8; ++s) - Zobrist::psq[c][pt][s] = rng.rand(); + for (Piece pc : Pieces) + for (Square s = SQ_A1; s <= SQ_H8; ++s) + Zobrist::psq[pc][s] = rng.rand(); for (File f = FILE_A; f <= FILE_H; ++f) Zobrist::enpassant[f] = rng.rand(); @@ -129,6 +156,7 @@ void Position::init() { } Zobrist::side = rng.rand(); + Zobrist::noPawns = rng.rand(); } @@ -160,8 +188,9 @@ 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 @@ -178,7 +207,7 @@ Position& Position::set(const string& fenStr, bool isChess960, StateInfo* si, Th std::memset(this, 0, sizeof(Position)); std::memset(si, 0, sizeof(StateInfo)); - std::fill_n(&pieceList[0][0][0], sizeof(pieceList) / sizeof(Square), SQ_NONE); + std::fill_n(&pieceList[0][0], sizeof(pieceList) / sizeof(Square), SQ_NONE); st = si; ss >> std::noskipws; @@ -187,14 +216,14 @@ Position& Position::set(const string& fenStr, bool isChess960, StateInfo* si, Th while ((ss >> token) && !isspace(token)) { if (isdigit(token)) - sq += Square(token - '0'); // Advance the given number of files + sq += (token - '0') * EAST; // Advance the given number of files else if (token == '/') - sq -= Square(16); + sq += 2 * SOUTH; else if ((idx = PieceToChar.find(token)) != string::npos) { - put_piece(color_of(Piece(idx)), type_of(Piece(idx)), sq); + put_piece(Piece(idx), sq); ++sq; } } @@ -238,7 +267,8 @@ 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 @@ -247,7 +277,7 @@ 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); @@ -292,8 +322,8 @@ void Position::set_castling_right(Color c, Square rfrom) { void Position::set_check_info(StateInfo* si) const { - si->blockersForKing[WHITE] = slider_blockers(pieces(BLACK), square(WHITE)); - si->blockersForKing[BLACK] = slider_blockers(pieces(WHITE), square(BLACK)); + si->blockersForKing[WHITE] = slider_blockers(pieces(BLACK), square(WHITE), si->pinners[BLACK]); + si->blockersForKing[BLACK] = slider_blockers(pieces(WHITE), square(BLACK), si->pinners[WHITE]); Square ksq = square(~sideToMove); @@ -313,7 +343,8 @@ 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); @@ -324,8 +355,8 @@ void Position::set_state(StateInfo* si) const { { Square s = pop_lsb(&b); Piece pc = piece_on(s); - si->key ^= Zobrist::psq[color_of(pc)][type_of(pc)][s]; - si->psq += PSQT::psq[color_of(pc)][type_of(pc)][s]; + si->key ^= Zobrist::psq[pc][s]; + si->psq += PSQT::psq[pc][s]; } if (si->epSquare != SQ_NONE) @@ -339,17 +370,38 @@ void Position::set_state(StateInfo* si) const { for (Bitboard b = pieces(PAWN); b; ) { Square s = pop_lsb(&b); - si->pawnKey ^= Zobrist::psq[color_of(piece_on(s))][PAWN][s]; + si->pawnKey ^= Zobrist::psq[piece_on(s)][s]; } - for (Color c = WHITE; c <= BLACK; ++c) - for (PieceType pt = PAWN; pt <= KING; ++pt) - for (int cnt = 0; cnt < pieceCount[c][pt]; ++cnt) - si->materialKey ^= Zobrist::psq[c][pt][cnt]; + for (Piece pc : Pieces) + { + if (type_of(pc) != PAWN && type_of(pc) != KING) + si->nonPawnMaterial[color_of(pc)] += pieceCount[pc] * PieceValue[MG][pc]; - for (Color c = WHITE; c <= BLACK; ++c) - for (PieceType pt = KNIGHT; pt <= QUEEN; ++pt) - si->nonPawnMaterial[c] += pieceCount[c][pt] * PieceValue[MG][pt]; + for (int cnt = 0; cnt < pieceCount[pc]; ++cnt) + si->materialKey ^= Zobrist::psq[pc][cnt]; + } +} + + +/// 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); } @@ -403,42 +455,35 @@ const string Position::fen() const { } -/// Position::game_phase() calculates the game phase interpolating total non-pawn -/// material between endgame and midgame limits. +/// 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. -Phase Position::game_phase() const { +Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const { - Value npm = st->nonPawnMaterial[WHITE] + st->nonPawnMaterial[BLACK]; + Bitboard blockers = 0; + pinners = 0; - npm = std::max(EndgameLimit, std::min(npm, MidgameLimit)); + // 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; - 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. - -Bitboard Position::slider_blockers(Bitboard sliders, Square s) const { - - Bitboard b, pinners, result = 0; - - // Pinners are sliders that attack 's' when a pinned piece is removed - pinners = ( (PseudoAttacks[ROOK ][s] & pieces(QUEEN, ROOK)) - | (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders; - - while (pinners) + while (snipers) { - b = between_bb(s, pop_lsb(&pinners)) & pieces(); - - if (!more_than_one(b)) - result |= b; + Square sniperSq = pop_lsb(&snipers); + Bitboard b = between_bb(s, sniperSq) & pieces(); + + if (b && !more_than_one(b)) + { + blockers |= b; + if (b & pieces(color_of(piece_on(s)))) + pinners |= sniperSq; + } } - return result; + return blockers; } @@ -450,7 +495,7 @@ 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)); } @@ -495,7 +540,7 @@ bool Position::legal(Move m) const { // A non-king move is legal if and only if it is not pinned or it // is moving along the ray towards or away from the king. - return !(pinned_pieces(us) & from) + return !(blockers_for_king(us) & from) || aligned(from, to_sq(m), square(us)); } @@ -544,7 +589,7 @@ 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 @@ -587,7 +632,7 @@ bool Position::gives_check(Move m) const { return true; // Is there a discovered check? - if ( (discovered_check_candidates() & from) + if ( (st->blockersForKing[~sideToMove] & from) && !aligned(from, to, square(~sideToMove))) return true; @@ -597,7 +642,7 @@ 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 +682,7 @@ 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 @@ -657,23 +702,24 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) { Color them = ~us; Square from = from_sq(m); Square to = to_sq(m); - PieceType pt = type_of(piece_on(from)); - PieceType captured = type_of(m) == ENPASSANT ? PAWN : type_of(piece_on(to)); + Piece pc = piece_on(from); + Piece captured = type_of(m) == ENPASSANT ? make_piece(them, PAWN) : piece_on(to); - assert(color_of(piece_on(from)) == us); - assert(piece_on(to) == NO_PIECE || color_of(piece_on(to)) == (type_of(m) != CASTLING ? them : us)); - assert(captured != KING); + assert(color_of(pc) == us); + assert(captured == NO_PIECE || color_of(captured) == (type_of(m) != CASTLING ? them : us)); + assert(type_of(captured) != KING); if (type_of(m) == CASTLING) { - assert(pt == KING); + assert(pc == make_piece(us, KING)); + assert(captured == make_piece(us, ROOK)); Square rfrom, rto; do_castling(us, from, to, rfrom, rto); - captured = NO_PIECE_TYPE; - st->psq += PSQT::psq[us][ROOK][rto] - PSQT::psq[us][ROOK][rfrom]; - k ^= Zobrist::psq[us][ROOK][rfrom] ^ Zobrist::psq[us][ROOK][rto]; + st->psq += PSQT::psq[captured][rto] - PSQT::psq[captured][rfrom]; + k ^= Zobrist::psq[captured][rfrom] ^ Zobrist::psq[captured][rto]; + captured = NO_PIECE; } if (captured) @@ -682,13 +728,13 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) { // If the captured piece is a pawn, update pawn hash key, otherwise // update non-pawn material. - if (captured == PAWN) + if (type_of(captured) == PAWN) { if (type_of(m) == ENPASSANT) { capsq -= pawn_push(us); - assert(pt == PAWN); + assert(pc == make_piece(us, PAWN)); assert(to == st->epSquare); assert(relative_rank(us, to) == RANK_6); assert(piece_on(to) == NO_PIECE); @@ -697,28 +743,28 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) { board[capsq] = NO_PIECE; // Not done by remove_piece() } - st->pawnKey ^= Zobrist::psq[them][PAWN][capsq]; + st->pawnKey ^= Zobrist::psq[captured][capsq]; } else st->nonPawnMaterial[them] -= PieceValue[MG][captured]; // Update board and piece lists - remove_piece(them, captured, capsq); + remove_piece(captured, capsq); // Update material hash key and prefetch access to materialTable - k ^= Zobrist::psq[them][captured][capsq]; - st->materialKey ^= Zobrist::psq[them][captured][pieceCount[them][captured]]; + k ^= Zobrist::psq[captured][capsq]; + st->materialKey ^= Zobrist::psq[captured][pieceCount[captured]]; prefetch(thisThread->materialTable[st->materialKey]); // Update incremental scores - st->psq -= PSQT::psq[them][captured][capsq]; + st->psq -= PSQT::psq[captured][capsq]; // Reset rule 50 counter st->rule50 = 0; } // Update hash key - k ^= Zobrist::psq[us][pt][from] ^ Zobrist::psq[us][pt][to]; + k ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to]; // Reset en passant square if (st->epSquare != SQ_NONE) @@ -737,55 +783,55 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) { // Move the piece. The tricky Chess960 castling is handled earlier if (type_of(m) != CASTLING) - move_piece(us, pt, from, to); + move_piece(pc, from, to); // If the moving piece is a pawn do some special extra work - if (pt == PAWN) + if (type_of(pc) == PAWN) { // Set en-passant square if the moved pawn can be captured if ( (int(to) ^ int(from)) == 16 && (attacks_from(to - pawn_push(us), us) & pieces(them, PAWN))) { - st->epSquare = (from + to) / 2; + st->epSquare = to - pawn_push(us); k ^= Zobrist::enpassant[file_of(st->epSquare)]; } else if (type_of(m) == PROMOTION) { - PieceType promotion = promotion_type(m); + Piece promotion = make_piece(us, promotion_type(m)); assert(relative_rank(us, to) == RANK_8); - assert(promotion >= KNIGHT && promotion <= QUEEN); + assert(type_of(promotion) >= KNIGHT && type_of(promotion) <= QUEEN); - remove_piece(us, PAWN, to); - put_piece(us, promotion, to); + remove_piece(pc, to); + put_piece(promotion, to); // Update hash keys - k ^= Zobrist::psq[us][PAWN][to] ^ Zobrist::psq[us][promotion][to]; - st->pawnKey ^= Zobrist::psq[us][PAWN][to]; - st->materialKey ^= Zobrist::psq[us][promotion][pieceCount[us][promotion]-1] - ^ Zobrist::psq[us][PAWN][pieceCount[us][PAWN]]; + k ^= Zobrist::psq[pc][to] ^ Zobrist::psq[promotion][to]; + st->pawnKey ^= Zobrist::psq[pc][to]; + st->materialKey ^= Zobrist::psq[promotion][pieceCount[promotion]-1] + ^ Zobrist::psq[pc][pieceCount[pc]]; // Update incremental score - st->psq += PSQT::psq[us][promotion][to] - PSQT::psq[us][PAWN][to]; + st->psq += PSQT::psq[promotion][to] - PSQT::psq[pc][to]; // Update material st->nonPawnMaterial[us] += PieceValue[MG][promotion]; } // Update pawn hash key and prefetch access to pawnsTable - st->pawnKey ^= Zobrist::psq[us][PAWN][from] ^ Zobrist::psq[us][PAWN][to]; - prefetch(thisThread->pawnsTable[st->pawnKey]); + st->pawnKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to]; + prefetch2(thisThread->pawnsTable[st->pawnKey]); // Reset rule 50 draw counter st->rule50 = 0; } // Update incremental scores - st->psq += PSQT::psq[us][pt][to] - PSQT::psq[us][pt][from]; + st->psq += PSQT::psq[pc][to] - PSQT::psq[pc][from]; // Set capture piece - st->capturedType = captured; + st->capturedPiece = captured; // Update the key with the final value st->key = k; @@ -814,20 +860,20 @@ void Position::undo_move(Move m) { Color us = sideToMove; Square from = from_sq(m); Square to = to_sq(m); - PieceType pt = type_of(piece_on(to)); + Piece pc = piece_on(to); assert(empty(from) || type_of(m) == CASTLING); - assert(st->capturedType != KING); + assert(type_of(st->capturedPiece) != KING); if (type_of(m) == PROMOTION) { assert(relative_rank(us, to) == RANK_8); - assert(pt == promotion_type(m)); - assert(pt >= KNIGHT && pt <= QUEEN); + assert(type_of(pc) == promotion_type(m)); + assert(type_of(pc) >= KNIGHT && type_of(pc) <= QUEEN); - remove_piece(us, pt, to); - put_piece(us, PAWN, to); - pt = PAWN; + remove_piece(pc, to); + pc = make_piece(us, PAWN); + put_piece(pc, to); } if (type_of(m) == CASTLING) @@ -837,9 +883,9 @@ void Position::undo_move(Move m) { } else { - move_piece(us, pt, to, from); // Put the piece back at the source square + move_piece(pc, to, from); // Put the piece back at the source square - if (st->capturedType) + if (st->capturedPiece) { Square capsq = to; @@ -847,14 +893,14 @@ void Position::undo_move(Move m) { { capsq -= pawn_push(us); - assert(pt == PAWN); + assert(type_of(pc) == PAWN); assert(to == st->previous->epSquare); assert(relative_rank(us, to) == RANK_6); assert(piece_on(capsq) == NO_PIECE); - assert(st->capturedType == PAWN); + assert(st->capturedPiece == make_piece(~us, PAWN)); } - put_piece(~us, st->capturedType, capsq); // Restore the captured piece + put_piece(st->capturedPiece, capsq); // Restore the captured piece } } @@ -867,7 +913,7 @@ void Position::undo_move(Move m) { /// Position::do_castling() is a helper used to do/undo a castling move. This -/// is a bit tricky, especially in Chess960. +/// is a bit tricky in Chess960 where from/to squares can overlap. template void Position::do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto) { @@ -877,11 +923,11 @@ void Position::do_castling(Color us, Square from, Square& to, Square& rfrom, Squ to = relative_square(us, kingSide ? SQ_G1 : SQ_C1); // Remove both pieces first since squares could overlap in Chess960 - remove_piece(us, KING, Do ? from : to); - remove_piece(us, ROOK, Do ? rfrom : rto); + remove_piece(make_piece(us, KING), Do ? from : to); + remove_piece(make_piece(us, ROOK), Do ? rfrom : rto); board[Do ? from : to] = board[Do ? rfrom : rto] = NO_PIECE; // Since remove_piece doesn't do it for us - put_piece(us, KING, Do ? to : from); - put_piece(us, ROOK, Do ? rto : rfrom); + put_piece(make_piece(us, KING), Do ? to : from); + put_piece(make_piece(us, ROOK), Do ? rto : rfrom); } @@ -931,127 +977,163 @@ void Position::undo_null_move() { Key Position::key_after(Move m) const { - Color us = sideToMove; Square from = from_sq(m); Square to = to_sq(m); - PieceType pt = type_of(piece_on(from)); - PieceType captured = type_of(piece_on(to)); + Piece pc = piece_on(from); + Piece captured = piece_on(to); Key k = st->key ^ Zobrist::side; if (captured) - k ^= Zobrist::psq[~us][captured][to]; + k ^= Zobrist::psq[captured][to]; - return k ^ Zobrist::psq[us][pt][to] ^ Zobrist::psq[us][pt][from]; + return k ^ Zobrist::psq[pc][to] ^ Zobrist::psq[pc][from]; } -/// 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; - - return see(m); -} - -Value Position::see(Move m) const { + // Only deal with normal moves, assume others pass a simple see + if (type_of(m) != NORMAL) + return VALUE_ZERO >= threshold; - Square from, to; - Bitboard occupied, attackers, stmAttackers; - Value swapList[32]; - int slIndex = 1; - PieceType captured; - Color stm; + Bitboard stmAttackers; + Square from = from_sq(m), to = to_sq(m); + PieceType nextVictim = type_of(piece_on(from)); + Color us = color_of(piece_on(from)); + Color stm = ~us; // First consider opponent's move + Value balance; // Values of the pieces taken by us minus opponent's ones - assert(is_ok(m)); + // The opponent may be able to recapture so this is the best result + // we can hope for. + balance = PieceValue[MG][piece_on(to)] - threshold; - 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) + return false; - // 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; + // Now assume the worst possible result: that the opponent can + // capture our piece for free. + balance -= PieceValue[MG][nextVictim]; - if (type_of(m) == ENPASSANT) - { - occupied ^= to - pawn_push(stm); // Remove the captured pawn - swapList[0] = PieceValue[MG][PAWN]; - } + // If it is enough (like in PxQ) then return immediately. Note that + // in case nextVictim == KING we always return here, this is ok + // if the given move is legal. + if (balance >= VALUE_ZERO) + return true; // 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]; - - // 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)); - - do { - assert(slIndex < 32); - - // Add the new entry to the swap list - swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured]; - - // Locate and remove the next least valuable attacker - captured = min_attacker(byTypeBB, to, stmAttackers, occupied, attackers); - stm = ~stm; + Bitboard occupied = pieces() ^ from ^ to; + Bitboard attackers = attackers_to(to, occupied) & occupied; + + while (true) + { stmAttackers = attackers & pieces(stm); - ++slIndex; - } while (stmAttackers && (captured != KING || (--slIndex, false))); // Stop before a king capture + // Don't allow pinned pieces to attack (except the king) as long as + // all pinners are on their original square. + if (!(st->pinners[~stm] & ~occupied)) + stmAttackers &= ~st->blockersForKing[stm]; + + // If stm has no more attackers then give up: stm loses + if (!stmAttackers) + 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]); + // Locate and remove the next least valuable attacker, and add to + // the bitboard 'attackers' the possibly X-ray attackers behind it. + nextVictim = min_attacker(byTypeBB, to, stmAttackers, occupied, attackers); - return swapList[0]; + stm = ~stm; // Switch side to move + + // Negamax the balance with alpha = balance, beta = balance+1 and + // add nextVictim's value. + // + // (balance, balance+1) -> (-balance-1, -balance) + // + assert(balance < VALUE_ZERO); + + balance = -balance - 1 - PieceValue[MG][nextVictim]; + + // If balance is still non-negative after giving away nextVictim then we + // win. The only thing to be careful about it is that we should revert + // stm if we captured with the king when the opponent still has attackers. + if (balance >= VALUE_ZERO) + { + if (nextVictim == KING && (attackers & pieces(stm))) + stm = ~stm; + break; + } + assert(nextVictim != KING); + } + return us != stm; // We break the above loop when stm loses } /// 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; } +// Position::has_repeated() tests whether there has been at least one repetition +// of positions since the last capture or pawn move. + +bool Position::has_repeated() const { + + StateInfo* stc = st; + while (true) + { + int i = 4, e = std::min(stc->rule50, stc->pliesFromNull); + + if (e < i) + return false; + + StateInfo* stp = st->previous->previous; + + do { + stp = stp->previous->previous; + + if (stp->key == stc->key) + return true; + + i += 2; + } while (i <= e); + + stc = stc->previous; + } +} + + /// Position::flip() flips position with the white and black sides reversed. This /// is only useful for debugging e.g. for finding evaluation symmetry bugs. @@ -1087,80 +1169,72 @@ 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 { + + constexpr bool Fast = true; // Quick (default) or full check? - const bool Fast = true; // Quick (default) or full check? + 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"); - enum { Default, King, Bitboards, State, Lists, Castling }; + if (Fast) + return true; - for (int step = Default; step <= (Fast ? Default : Castling); step++) + if ( pieceCount[W_KING] != 1 + || pieceCount[B_KING] != 1 + || attackers_to(square(~sideToMove)) & pieces(sideToMove)) + assert(0 && "pos_is_ok: Kings"); + + if ( (pieces(PAWN) & (Rank1BB | Rank8BB)) + || pieceCount[W_PAWN] > 8 + || pieceCount[B_PAWN] > 8) + assert(0 && "pos_is_ok: Pawns"); + + if ( (pieces(WHITE) & pieces(BLACK)) + || (pieces(WHITE) | pieces(BLACK)) != pieces() + || popcount(pieces(WHITE)) > 16 + || popcount(pieces(BLACK)) > 16) + assert(0 && "pos_is_ok: Bitboards"); + + 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"); + + StateInfo si = *st; + set_state(&si); + if (std::memcmp(&si, st, sizeof(StateInfo))) + assert(0 && "pos_is_ok: State"); + + for (Piece pc : Pieces) { - 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 ( 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 == 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; + 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"); + } - if (step == Bitboards) + for (Color c = WHITE; c <= BLACK; ++c) + for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1)) { - if ( (pieces(WHITE) & pieces(BLACK)) - ||(pieces(WHITE) | pieces(BLACK)) != pieces()) - return false; + if (!can_castle(c | s)) + continue; - for (PieceType p1 = PAWN; p1 <= KING; ++p1) - for (PieceType p2 = PAWN; p2 <= KING; ++p2) - if (p1 != p2 && (pieces(p1) & pieces(p2))) - return false; + 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"); } - if (step == State) - { - StateInfo si = *st; - set_state(&si); - if (std::memcmp(&si, st, sizeof(StateInfo))) - return false; - } - - if (step == Lists) - for (Color c = WHITE; c <= BLACK; ++c) - for (PieceType pt = PAWN; pt <= KING; ++pt) - { - if (pieceCount[c][pt] != popcount(pieces(c, pt))) - return false; - - for (int i = 0; i < pieceCount[c][pt]; ++i) - if ( board[pieceList[c][pt][i]] != make_piece(c, pt) - || index[pieceList[c][pt][i]] != i) - return false; - } - - 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; - } - } - return true; }