From: Marco Costalba Date: Fri, 23 Jul 2010 08:38:19 +0000 (+0200) Subject: Rewrite Position::from_fen() X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=839088205edd88eee9852c21442424cc66941ccb Rewrite Position::from_fen() Complete rewrite the function and extend compatibility also to X-FEN notation for Chess960. We are now able to read standard FEN, Shredder-FEN and X-FEN. No functional change. Signed-off-by: Marco Costalba --- diff --git a/src/benchmark.cpp b/src/benchmark.cpp index e23afb14..c554008b 100644 --- a/src/benchmark.cpp +++ b/src/benchmark.cpp @@ -51,7 +51,7 @@ const string BenchmarkPositions[] = { "r1bq1r1k/b1p1npp1/p2p3p/1p6/3PP3/1B2NN2/PP3PPP/R2Q1RK1 w - - 1 16", "3r1rk1/p5pp/bpp1pp2/8/q1PP1P2/b3P3/P2NQRPP/1R2B1K1 b - - 6 22", "r1q2rk1/2p1bppp/2Pp4/p6b/Q1PNp3/4B3/PP1R1PPP/2K4R w - - 2 18", - "4k2r/1pb2ppp/1p2p3/1R1p4/3P4/2r1PN2/P4PPP/1R4K1 b - 3 22", + "4k2r/1pb2ppp/1p2p3/1R1p4/3P4/2r1PN2/P4PPP/1R4K1 b - - 3 22", "3q2k1/pb3p1p/4pbp1/2r5/PpN2N2/1P2P2P/5PP1/Q2R2K1 b - - 4 26" }; diff --git a/src/material.cpp b/src/material.cpp index 973d3684..03db87c8 100644 --- a/src/material.cpp +++ b/src/material.cpp @@ -404,7 +404,7 @@ Key EndgameFunctions::buildKey(const string& keyCode) { s << char(upcase ? toupper(keyCode[i]) : tolower(keyCode[i])); } - s << 8 - keyCode.length() << "/8/8/8/8/8/8/8 w -"; + s << 8 - keyCode.length() << "/8/8/8/8/8/8/8 w - -"; return Position(s.str(), 0).get_material_key(); } diff --git a/src/position.cpp b/src/position.cpp index 537e574f..1942abb0 100644 --- a/src/position.cpp +++ b/src/position.cpp @@ -26,6 +26,7 @@ #include #include #include +#include #include "bitcount.h" #include "mersenne.h" @@ -38,6 +39,8 @@ #include "ucioption.h" using std::string; +using std::cout; +using std::endl; //// @@ -111,135 +114,104 @@ void Position::detach() { /// correct (this is assumed to be the responsibility of the GUI). void Position::from_fen(const string& fen) { +/* + A FEN string defines a particular position using only the ASCII character set. + + A FEN string contains six fields. The separator between fields is a space. The fields are: + + 1) Piece placement (from white's perspective). Each rank is described, starting with rank 8 and ending + with rank 1; within each rank, the contents of each square are described from file a through file h. + Following the Standard Algebraic Notation (SAN), each piece is identified by a single letter taken + from the standard English names. White pieces are designated using upper-case letters ("PNBRQK") + while Black take lowercase ("pnbrqk"). Blank squares are noted using digits 1 through 8 (the number + of blank squares), and "/" separate ranks. + + 2) Active color. "w" means white moves next, "b" means black. + + 3) Castling availability. If neither side can castle, this is "-". Otherwise, this has one or more + letters: "K" (White can castle kingside), "Q" (White can castle queenside), "k" (Black can castle + kingside), and/or "q" (Black can castle queenside). + + 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. + + 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 fifty-move rule. + + 6) Fullmove number: The number of the full move. It starts at 1, and is incremented after Black's move. +*/ static const string pieceLetters = "KQRBNPkqrbnp"; static const Piece pieces[] = { WK, WQ, WR, WB, WN, WP, BK, BQ, BR, BB, BN, BP }; - clear(); - - // Board Rank rank = RANK_8; File file = FILE_A; - size_t i = 0; - for ( ; fen[i] != ' '; i++) + size_t idx; + + std::istringstream ss(fen); + char token; + + clear(); + + // 1. Piece placement field + while (ss.get(token) && token != ' ') { - if (isdigit(fen[i])) + if (isdigit(token)) { // Skip the given number of files - file += (fen[i] - '1' + 1); + file += token - '1' + 1; continue; } - else if (fen[i] == '/') + else if (token == '/') { file = FILE_A; rank--; continue; } - size_t idx = pieceLetters.find(fen[i]); + + idx = pieceLetters.find(token); if (idx == string::npos) - { - std::cout << "Error in FEN at character " << i << std::endl; - return; - } - Square square = make_square(file, rank); - put_piece(pieces[idx], square); + goto incorrect_fen; + + put_piece(pieces[idx], make_square(file, rank)); file++; } - // Side to move - i++; - if (fen[i] != 'w' && fen[i] != 'b') - { - std::cout << "Error in FEN at character " << i << std::endl; - return; - } - sideToMove = (fen[i] == 'w' ? WHITE : BLACK); + // 2. Active color + if (!ss.get(token) || (token != 'w' && token != 'b')) + goto incorrect_fen; - // Castling rights - i++; - if (fen[i] != ' ') + sideToMove = (token == 'w' ? WHITE : BLACK); + + if (!ss.get(token) || token != ' ') + goto incorrect_fen; + + // 3. Castling availability + while (ss.get(token) && token != ' ') { - std::cout << "Error in FEN at character " << i << std::endl; - return; - } + if (token == '-') + continue; - i++; - while (strchr("KQkqabcdefghABCDEFGH-", fen[i])) { - if (fen[i] == '-') - { - i++; - break; - } - else if (fen[i] == 'K') allow_oo(WHITE); - else if (fen[i] == 'Q') allow_ooo(WHITE); - else if (fen[i] == 'k') allow_oo(BLACK); - else if (fen[i] == 'q') allow_ooo(BLACK); - else if (fen[i] >= 'A' && fen[i] <= 'H') { - File rookFile, kingFile = FILE_NONE; - for (Square square = SQ_B1; square <= SQ_G1; square++) - if (piece_on(square) == WK) - kingFile = square_file(square); - if (kingFile == FILE_NONE) { - std::cout << "Error in FEN at character " << i << std::endl; - return; - } - initialKFile = kingFile; - rookFile = File(fen[i] - 'A') + FILE_A; - if (rookFile < initialKFile) { - allow_ooo(WHITE); - initialQRFile = rookFile; - } - else { - allow_oo(WHITE); - initialKRFile = rookFile; - } - } - else if (fen[i] >= 'a' && fen[i] <= 'h') { - File rookFile, kingFile = FILE_NONE; - for (Square square = SQ_B8; square <= SQ_G8; square++) - if (piece_on(square) == BK) - kingFile = square_file(square); - if (kingFile == FILE_NONE) { - std::cout << "Error in FEN at character " << i << std::endl; - return; - } - initialKFile = kingFile; - rookFile = File(fen[i] - 'a') + FILE_A; - if (rookFile < initialKFile) { - allow_ooo(BLACK); - initialQRFile = rookFile; - } - else { - allow_oo(BLACK); - initialKRFile = rookFile; - } - } - else { - std::cout << "Error in FEN at character " << i << std::endl; - return; - } - i++; + if (!set_castling_rights(token)) + goto incorrect_fen; } - // Skip blanks - while (fen[i] == ' ') - i++; - - // En passant square -- ignore if no capture is possible - if ( i <= fen.length() - 2 - && (fen[i] >= 'a' && fen[i] <= 'h') - && (fen[i+1] == '3' || fen[i+1] == '6')) + // 4. En passant square -- ignore if no capture is possible + char col, row; + if ( (ss.get(col) && (col >= 'a' && col <= 'h')) + && (ss.get(row) && (row == '3' || row == '6'))) { - Square fenEpSquare = square_from_string(fen.substr(i, 2)); + Square fenEpSquare = make_square(file_from_char(col), rank_from_char(row)); Color them = opposite_color(sideToMove); + if (attacks_from(fenEpSquare, them) & this->pieces(PAWN, sideToMove)) - st->epSquare = square_from_string(fen.substr(i, 2)); + st->epSquare = fenEpSquare; } - // Various initialisation - for (Square sq = SQ_A1; sq <= SQ_H8; sq++) - castleRightsMask[sq] = ALL_CASTLES; + // 5-6. Halfmove clock and fullmove number are not parsed + // Various initialisations castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO|WHITE_OOO); castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO|BLACK_OOO); castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO; @@ -255,6 +227,67 @@ void Position::from_fen(const string& fen) { st->value = compute_value(); st->npMaterial[WHITE] = compute_non_pawn_material(WHITE); st->npMaterial[BLACK] = compute_non_pawn_material(BLACK); + return; + +incorrect_fen: + cout << "Error in FEN string: " << fen << endl; +} + + +/// Position::set_castling_rights() sets castling parameters castling avaiability. +/// This function is compatible with 3 standards: Normal FEN standard, Shredder-FEN +/// that uses the letters of the columns on which the rooks began the game instead +/// of KQkq and also X-FEN standard that, in case of Chess960, if an inner Rook is +/// associated with the castling right, the traditional castling tag will be replaced +/// by the file letter of the involved rook as for the Shredder-FEN. + +bool Position::set_castling_rights(char token) { + + Color c = token >= 'a' ? BLACK : WHITE; + Square sqA = (c == WHITE ? SQ_A1 : SQ_A8); + Square sqH = (c == WHITE ? SQ_H1 : SQ_H8); + Piece rook = (c == WHITE ? WR : BR); + + initialKFile = square_file(king_square(c)); + token = char(toupper(token)); + + if (token == 'K') + { + for (Square sq = sqH; sq >= sqA; sq--) + if (piece_on(sq) == rook) + { + allow_oo(c); + initialKRFile = square_file(sq); + break; + } + } + else if (token == 'Q') + { + for (Square sq = sqA; sq <= sqH; sq++) + if (piece_on(sq) == rook) + { + allow_ooo(c); + initialQRFile = square_file(sq); + break; + } + } + else if (token >= 'A' && token <= 'H') + { + File rookFile = File(token - 'A') + FILE_A; + if (rookFile < initialKFile) + { + allow_ooo(c); + initialQRFile = rookFile; + } + else + { + allow_oo(c); + initialKRFile = rookFile; + } + } + else return false; + + return true; } @@ -337,16 +370,16 @@ void Position::print(Move m) const { RequestPending = true; - std::cout << std::endl; + cout << endl; if (m != MOVE_NONE) { Position p(*this, thread()); string col = (color_of_piece_on(move_from(m)) == BLACK ? ".." : ""); - std::cout << "Move is: " << col << move_to_san(p, m) << std::endl; + cout << "Move is: " << col << move_to_san(p, m) << endl; } for (Rank rank = RANK_8; rank >= RANK_1; rank--) { - std::cout << "+---+---+---+---+---+---+---+---+" << std::endl; + cout << "+---+---+---+---+---+---+---+---+" << endl; for (File file = FILE_A; file <= FILE_H; file++) { Square sq = make_square(file, rank); @@ -355,13 +388,13 @@ void Position::print(Move m) const { piece = NO_PIECE; char col = (color_of_piece_on(sq) == BLACK ? '=' : ' '); - std::cout << '|' << col << pieceLetters[piece] << col; + cout << '|' << col << pieceLetters[piece] << col; } - std::cout << '|' << std::endl; + cout << '|' << endl; } - std::cout << "+---+---+---+---+---+---+---+---+" << std::endl - << "Fen is: " << to_fen() << std::endl - << "Key is: " << st->key << std::endl; + cout << "+---+---+---+---+---+---+---+---+" << endl + << "Fen is: " << to_fen() << endl + << "Key is: " << st->key << endl; RequestPending = false; } @@ -1474,6 +1507,9 @@ void Position::clear() { for (int j = 0; j < 16; j++) pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE; + for (Square sq = SQ_A1; sq <= SQ_H8; sq++) + castleRightsMask[sq] = ALL_CASTLES; + sideToMove = WHITE; initialKFile = FILE_E; initialKRFile = FILE_H; @@ -1799,9 +1835,6 @@ void Position::flipped_copy(const Position& pos) { initialKRFile = pos.initialKRFile; initialQRFile = pos.initialQRFile; - for (Square sq = SQ_A1; sq <= SQ_H8; sq++) - castleRightsMask[sq] = ALL_CASTLES; - castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO | WHITE_OOO); castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO | BLACK_OOO); castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO; diff --git a/src/position.h b/src/position.h index 826fa13b..4854b29d 100644 --- a/src/position.h +++ b/src/position.h @@ -294,6 +294,7 @@ private: void put_piece(Piece p, Square s); void allow_oo(Color c); void allow_ooo(Color c); + bool set_castling_rights(char token); // Helper functions for doing and undoing moves void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);