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Chess: Refactor game logic into LibChess for use in engines
In the future UCI protocol stuff will also go into LibChess.
This commit is contained in:
Peter Elliott
Andreas Kling
parent
ffece9cfba
commit
d2cb5e0f48
7 changed files with 165 additions and 148 deletions
552
Libraries/LibChess/Chess.cpp
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552
Libraries/LibChess/Chess.cpp
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/*
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* Copyright (c) 2020, the SerenityOS developers.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <AK/Assertions.h>
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#include <AK/LogStream.h>
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#include <AK/String.h>
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#include <AK/StringBuilder.h>
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#include <AK/Vector.h>
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#include <LibChess/Chess.h>
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#include <stdlib.h>
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namespace Chess {
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String char_for_piece(Chess::Type type)
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{
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switch (type) {
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case Type::Knight:
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return "N";
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case Type::Bishop:
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return "B";
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case Type::Rook:
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return "R";
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case Type::Queen:
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return "Q";
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case Type::King:
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return "K";
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case Type::Pawn:
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default:
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return "";
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}
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}
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Colour opposing_colour(Colour colour)
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{
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return (colour == Colour::White) ? Colour::Black : Colour::White;
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}
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Square::Square(const StringView& name)
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{
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ASSERT(name.length() == 2);
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char filec = name[0];
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char rankc = name[1];
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if (filec >= 'a' && filec <= 'h') {
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file = filec - 'a';
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} else if (filec >= 'A' && filec <= 'H') {
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file = filec - 'A';
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} else {
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ASSERT_NOT_REACHED();
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}
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if (rankc >= '1' && rankc <= '8') {
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rank = rankc - '1';
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} else {
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ASSERT_NOT_REACHED();
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}
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}
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String Square::to_algebraic() const
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{
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StringBuilder builder;
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builder.append(file - 'a');
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builder.append(rank - '1');
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return builder.build();
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}
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String Move::to_long_algebraic() const
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{
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StringBuilder builder;
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builder.append(from.to_algebraic());
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builder.append(to.to_algebraic());
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builder.append(char_for_piece(promote_to).to_lowercase());
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return builder.build();
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}
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Board::Board()
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{
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// Fill empty spaces.
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for (unsigned rank = 2; rank < 6; ++rank) {
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for (unsigned file = 0; file < 8; ++file) {
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set_piece({ rank, file }, EmptyPiece);
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}
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}
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// Fill white pawns.
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for (unsigned file = 0; file < 8; ++file) {
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set_piece({ 1, file }, { Colour::White, Type::Pawn });
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}
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// Fill black pawns.
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for (unsigned file = 0; file < 8; ++file) {
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set_piece({ 6, file }, { Colour::Black, Type::Pawn });
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}
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// Fill while pieces.
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set_piece(Square("a1"), { Colour::White, Type::Rook });
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set_piece(Square("b1"), { Colour::White, Type::Knight });
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set_piece(Square("c1"), { Colour::White, Type::Bishop });
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set_piece(Square("d1"), { Colour::White, Type::Queen });
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set_piece(Square("e1"), { Colour::White, Type::King });
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set_piece(Square("f1"), { Colour::White, Type::Bishop });
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set_piece(Square("g1"), { Colour::White, Type::Knight });
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set_piece(Square("h1"), { Colour::White, Type::Rook });
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// Fill black pieces.
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set_piece(Square("a8"), { Colour::Black, Type::Rook });
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set_piece(Square("b8"), { Colour::Black, Type::Knight });
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set_piece(Square("c8"), { Colour::Black, Type::Bishop });
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set_piece(Square("d8"), { Colour::Black, Type::Queen });
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set_piece(Square("e8"), { Colour::Black, Type::King });
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set_piece(Square("f8"), { Colour::Black, Type::Bishop });
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set_piece(Square("g8"), { Colour::Black, Type::Knight });
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set_piece(Square("h8"), { Colour::Black, Type::Rook });
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}
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Piece Board::get_piece(const Square& square) const
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{
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ASSERT(square.rank < 8);
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ASSERT(square.file < 8);
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return m_board[square.rank][square.file];
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}
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Piece Board::set_piece(const Square& square, const Piece& piece)
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{
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ASSERT(square.rank < 8);
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ASSERT(square.file < 8);
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return m_board[square.rank][square.file] = piece;
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}
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bool Board::is_legal(const Move& move, Colour colour) const
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{
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if (colour == Colour::None)
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colour = turn();
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if (!is_legal_no_check(move, colour))
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return false;
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Board clone = *this;
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clone.apply_illegal_move(move, colour);
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if (clone.in_check(colour))
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return false;
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// Don't allow castling through check or out of check.
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Vector<Square> check_squares;
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if (colour == Colour::White && move.from == Square("e1") && get_piece(Square("e1")) == Piece(Colour::White, Type::King)) {
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if (move.to == Square("a1") || move.to == Square("c1")) {
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check_squares = { Square("e1"), Square("d1"), Square("c1") };
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} else if (move.to == Square("h1") || move.to == Square("g1")) {
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check_squares = { Square("e1"), Square("f1"), Square("g1") };
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}
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} else if (colour == Colour::Black && move.from == Square("e8") && get_piece(Square("e8")) == Piece(Colour::Black, Type::King)) {
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if (move.to == Square("a8") || move.to == Square("c8")) {
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check_squares = { Square("e8"), Square("d8"), Square("c8") };
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} else if (move.to == Square("h8") || move.to == Square("g8")) {
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check_squares = { Square("e8"), Square("f8"), Square("g8") };
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}
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}
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for (auto& square : check_squares) {
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Board clone = *this;
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clone.set_piece(move.from, EmptyPiece);
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clone.set_piece(square, { colour, Type::King });
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if (clone.in_check(colour))
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return false;
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}
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return true;
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}
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bool Board::is_legal_no_check(const Move& move, Colour colour) const
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{
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auto piece = get_piece(move.from);
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if (piece.colour != colour)
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return false;
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if (move.to.rank > 7 || move.to.file > 7)
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return false;
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if (piece.type != Type::Pawn && move.promote_to != Type::None)
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return false;
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if (move.promote_to == Type::Pawn || move.promote_to == Type::King)
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return false;
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if (piece.type == Type::Pawn) {
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int dir = (colour == Colour::White) ? +1 : -1;
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unsigned start_rank = (colour == Colour::White) ? 1 : 6;
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unsigned other_start_rank = (colour == Colour::White) ? 6 : 1;
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unsigned en_passant_rank = (colour == Colour::White) ? 4 : 3;
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unsigned promotion_rank = (colour == Colour::White) ? 7 : 0;
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if (move.to.rank == promotion_rank) {
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if (move.promote_to == Type::Pawn || move.promote_to == Type::King || move.promote_to == Type::None)
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return false;
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} else if (move.promote_to != Type::None) {
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return false;
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}
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if (move.to.rank == move.from.rank + dir && move.to.file == move.from.file && get_piece(move.to).type == Type::None) {
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// Regular pawn move.
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return true;
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} else if (move.to.rank == move.from.rank + dir && (move.to.file == move.from.file + 1 || move.to.file == move.from.file - 1)) {
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Move en_passant_last_move = { { other_start_rank, move.to.file }, { en_passant_rank, move.to.file } };
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if (get_piece(move.to).colour == opposing_colour(colour)) {
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// Pawn capture.
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return true;
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} else if (m_last_move.has_value() && move.from.rank == en_passant_rank && m_last_move.value() == en_passant_last_move
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&& get_piece(en_passant_last_move.to) == Piece(opposing_colour(colour), Type::Pawn)) {
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// En passant.
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return true;
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}
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} else if (move.from.rank == start_rank && move.to.rank == move.from.rank + (2 * dir) && move.to.file == move.from.file
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&& get_piece(move.to).type == Type::None && get_piece({ move.from.rank + dir, move.from.file }).type == Type::None) {
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// 2 square pawn move from initial position.
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return true;
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}
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return false;
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} else if (piece.type == Type::Knight) {
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int rank_delta = abs(move.to.rank - move.from.rank);
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int file_delta = abs(move.to.file - move.from.file);
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if (get_piece(move.to).colour != colour && max(rank_delta, file_delta) == 2 && min(rank_delta, file_delta) == 1) {
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return true;
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}
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} else if (piece.type == Type::Bishop) {
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int rank_delta = move.to.rank - move.from.rank;
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int file_delta = move.to.file - move.from.file;
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if (abs(rank_delta) == abs(file_delta)) {
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int dr = rank_delta / abs(rank_delta);
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int df = file_delta / abs(file_delta);
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for (Square sq = move.from; sq != move.to; sq.rank += dr, sq.file += df) {
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if (get_piece(sq).type != Type::None && sq != move.from) {
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return false;
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}
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}
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if (get_piece(move.to).colour != colour) {
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return true;
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}
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}
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} else if (piece.type == Type::Rook) {
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int rank_delta = move.to.rank - move.from.rank;
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int file_delta = move.to.file - move.from.file;
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if (rank_delta == 0 || file_delta == 0) {
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int dr = (rank_delta) ? rank_delta / abs(rank_delta) : 0;
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int df = (file_delta) ? file_delta / abs(file_delta) : 0;
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for (Square sq = move.from; sq != move.to; sq.rank += dr, sq.file += df) {
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if (get_piece(sq).type != Type::None && sq != move.from) {
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return false;
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}
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}
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if (get_piece(move.to).colour != colour) {
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return true;
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}
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}
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} else if (piece.type == Type::Queen) {
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int rank_delta = move.to.rank - move.from.rank;
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int file_delta = move.to.file - move.from.file;
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if (abs(rank_delta) == abs(file_delta) || rank_delta == 0 || file_delta == 0) {
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int dr = (rank_delta) ? rank_delta / abs(rank_delta) : 0;
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int df = (file_delta) ? file_delta / abs(file_delta) : 0;
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for (Square sq = move.from; sq != move.to; sq.rank += dr, sq.file += df) {
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if (get_piece(sq).type != Type::None && sq != move.from) {
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return false;
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}
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}
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if (get_piece(move.to).colour != colour) {
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return true;
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}
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}
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} else if (piece.type == Type::King) {
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int rank_delta = move.to.rank - move.from.rank;
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int file_delta = move.to.file - move.from.file;
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if (abs(rank_delta) <= 1 && abs(file_delta) <= 1) {
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if (get_piece(move.to).colour != colour) {
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return true;
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}
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}
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if (colour == Colour::White) {
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if ((move.to == Square("a1") || move.to == Square("c1")) && m_white_can_castle_queenside && get_piece(Square("b1")).type == Type::None && get_piece(Square("c1")).type == Type::None && get_piece(Square("d1")).type == Type::None) {
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return true;
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} else if ((move.to == Square("h1") || move.to == Square("g1")) && m_white_can_castle_kingside && get_piece(Square("f1")).type == Type::None && get_piece(Square("g1")).type == Type::None) {
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return true;
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}
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} else {
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if ((move.to == Square("a8") || move.to == Square("c8")) && m_black_can_castle_queenside && get_piece(Square("b8")).type == Type::None && get_piece(Square("c8")).type == Type::None && get_piece(Square("d8")).type == Type::None) {
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return true;
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} else if ((move.to == Square("h8") || move.to == Square("g8")) && m_black_can_castle_kingside && get_piece(Square("f8")).type == Type::None && get_piece(Square("g8")).type == Type::None) {
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return true;
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}
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}
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}
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return false;
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}
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bool Board::in_check(Colour colour) const
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{
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Square king_square = { 50, 50 };
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Square::for_each([&](const Square& square) {
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if (get_piece(square) == Piece(colour, Type::King)) {
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king_square = square;
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return IterationDecision::Break;
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}
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return IterationDecision::Continue;
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});
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bool check = false;
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Square::for_each([&](const Square& square) {
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if (is_legal({ square, king_square }, opposing_colour(colour))) {
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check = true;
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return IterationDecision::Break;
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} else if (get_piece(square) == Piece(opposing_colour(colour), Type::King) && is_legal_no_check({ square, king_square }, opposing_colour(colour))) {
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// The King is a special case, because it would be in check if it put the opposing king in check.
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check = true;
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return IterationDecision::Break;
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}
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return IterationDecision::Continue;
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});
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return check;
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}
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bool Board::apply_move(const Move& move, Colour colour)
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{
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if (colour == Colour::None)
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colour = turn();
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if (!is_legal(move, colour))
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return false;
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return apply_illegal_move(move, colour);
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}
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bool Board::apply_illegal_move(const Move& move, Colour colour)
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{
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Board clone = *this;
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clone.m_previous_states = {};
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auto state_count = 0;
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if (m_previous_states.contains(clone))
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state_count = m_previous_states.get(clone).value();
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m_previous_states.set(clone, state_count + 1);
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m_turn = opposing_colour(colour);
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m_last_move = move;
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m_moves_since_capture++;
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if (move.from == Square("a1") || move.to == Square("a1") || move.from == Square("e1"))
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m_white_can_castle_queenside = false;
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if (move.from == Square("h1") || move.to == Square("h1") || move.from == Square("e1"))
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m_white_can_castle_kingside = false;
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if (move.from == Square("a8") || move.to == Square("a8") || move.from == Square("e8"))
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m_black_can_castle_queenside = false;
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if (move.from == Square("h8") || move.to == Square("h8") || move.from == Square("e8"))
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m_black_can_castle_kingside = false;
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if (colour == Colour::White && move.from == Square("e1") && get_piece(Square("e1")) == Piece(Colour::White, Type::King)) {
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if (move.to == Square("a1") || move.to == Square("c1")) {
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set_piece(Square("e1"), EmptyPiece);
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set_piece(Square("a1"), EmptyPiece);
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set_piece(Square("c1"), { Colour::White, Type::King });
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set_piece(Square("d1"), { Colour::White, Type::Rook });
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return true;
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} else if (move.to == Square("h1") || move.to == Square("g1")) {
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set_piece(Square("e1"), EmptyPiece);
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set_piece(Square("h1"), EmptyPiece);
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set_piece(Square("g1"), { Colour::White, Type::King });
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set_piece(Square("f1"), { Colour::White, Type::Rook });
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return true;
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}
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} else if (colour == Colour::Black && move.from == Square("e8") && get_piece(Square("e8")) == Piece(Colour::Black, Type::King)) {
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if (move.to == Square("a8") || move.to == Square("c8")) {
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set_piece(Square("e8"), EmptyPiece);
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set_piece(Square("a8"), EmptyPiece);
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set_piece(Square("c8"), { Colour::White, Type::King });
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set_piece(Square("d8"), { Colour::White, Type::Rook });
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return true;
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} else if (move.to == Square("h8") || move.to == Square("g8")) {
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set_piece(Square("e8"), EmptyPiece);
|
||||
set_piece(Square("h8"), EmptyPiece);
|
||||
set_piece(Square("g8"), { Colour::Black, Type::King });
|
||||
set_piece(Square("f8"), { Colour::Black, Type::Rook });
|
||||
return true;
|
||||
}
|
||||
}
|
||||
|
||||
if (get_piece(move.from).type == Type::Pawn && ((colour == Colour::Black && move.to.rank == 0) || (colour == Colour::White && move.to.rank == 7))) {
|
||||
// Pawn Promotion
|
||||
set_piece(move.to, { colour, move.promote_to });
|
||||
set_piece(move.from, EmptyPiece);
|
||||
return true;
|
||||
}
|
||||
|
||||
if (get_piece(move.from).type == Type::Pawn && move.from.file != move.to.file && get_piece(move.to).type == Type::None) {
|
||||
// En passant.
|
||||
if (colour == Colour::White) {
|
||||
set_piece({ move.to.rank - 1, move.to.file }, EmptyPiece);
|
||||
} else {
|
||||
set_piece({ move.to.rank + 1, move.to.file }, EmptyPiece);
|
||||
}
|
||||
m_moves_since_capture = 0;
|
||||
}
|
||||
|
||||
if (get_piece(move.to).colour != Colour::None)
|
||||
m_moves_since_capture = 0;
|
||||
|
||||
set_piece(move.to, get_piece(move.from));
|
||||
set_piece(move.from, EmptyPiece);
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
Board::Result Board::game_result() const
|
||||
{
|
||||
bool sufficient_material = false;
|
||||
bool no_more_pieces_allowed = false;
|
||||
Optional<Square> bishop;
|
||||
Square::for_each([&](Square sq) {
|
||||
if (get_piece(sq).type == Type::Queen || get_piece(sq).type == Type::Rook || get_piece(sq).type == Type::Pawn) {
|
||||
sufficient_material = true;
|
||||
return IterationDecision::Break;
|
||||
}
|
||||
|
||||
if (get_piece(sq).type != Type::None && get_piece(sq).type != Type::King && no_more_pieces_allowed) {
|
||||
sufficient_material = true;
|
||||
return IterationDecision::Break;
|
||||
}
|
||||
|
||||
if (get_piece(sq).type == Type::Knight)
|
||||
no_more_pieces_allowed = true;
|
||||
|
||||
if (get_piece(sq).type == Type::Bishop) {
|
||||
if (bishop.has_value()) {
|
||||
if (get_piece(sq).colour == get_piece(bishop.value()).colour) {
|
||||
sufficient_material = true;
|
||||
return IterationDecision::Break;
|
||||
} else if (sq.is_light() != bishop.value().is_light()) {
|
||||
sufficient_material = true;
|
||||
return IterationDecision::Break;
|
||||
}
|
||||
no_more_pieces_allowed = true;
|
||||
} else {
|
||||
bishop = sq;
|
||||
}
|
||||
}
|
||||
|
||||
return IterationDecision::Continue;
|
||||
});
|
||||
|
||||
if (!sufficient_material)
|
||||
return Result::InsufficientMaterial;
|
||||
|
||||
bool are_legal_moves = false;
|
||||
generate_moves([&](Move m) {
|
||||
(void)m;
|
||||
are_legal_moves = true;
|
||||
return IterationDecision::Break;
|
||||
});
|
||||
|
||||
if (are_legal_moves) {
|
||||
if (m_moves_since_capture >= 75 * 2)
|
||||
return Result::SeventyFiveMoveRule;
|
||||
if (m_moves_since_capture == 50 * 2)
|
||||
return Result::FiftyMoveRule;
|
||||
|
||||
auto repeats = m_previous_states.get(*this);
|
||||
if (repeats.has_value()) {
|
||||
if (repeats.value() == 3)
|
||||
return Result::ThreeFoldRepitition;
|
||||
if (repeats.value() >= 5)
|
||||
return Result::FiveFoldRepitition;
|
||||
}
|
||||
|
||||
return Result::NotFinished;
|
||||
}
|
||||
|
||||
if (in_check(turn()))
|
||||
return Result::CheckMate;
|
||||
|
||||
return Result::StaleMate;
|
||||
}
|
||||
|
||||
bool Board::is_promotion_move(const Move& move, Colour colour) const
|
||||
{
|
||||
if (colour == Colour::None)
|
||||
colour = turn();
|
||||
|
||||
Move queen_move = move;
|
||||
queen_move.promote_to = Type::Queen;
|
||||
if (!is_legal(queen_move, colour))
|
||||
return false;
|
||||
|
||||
if (get_piece(move.from).type == Type::Pawn && ((colour == Colour::Black && move.to.rank == 0) || (colour == Colour::White && move.to.rank == 7)))
|
||||
return true;
|
||||
|
||||
return false;
|
||||
}
|
||||
|
||||
bool Board::operator==(const Board& other) const
|
||||
{
|
||||
bool equal_squares = true;
|
||||
Square::for_each([&](Square sq) {
|
||||
if (get_piece(sq) != other.get_piece(sq)) {
|
||||
equal_squares = false;
|
||||
return IterationDecision::Break;
|
||||
}
|
||||
return IterationDecision::Continue;
|
||||
});
|
||||
if (!equal_squares)
|
||||
return false;
|
||||
|
||||
if (m_white_can_castle_queenside != other.m_white_can_castle_queenside)
|
||||
return false;
|
||||
if (m_white_can_castle_kingside != other.m_white_can_castle_kingside)
|
||||
return false;
|
||||
if (m_black_can_castle_queenside != other.m_black_can_castle_queenside)
|
||||
return false;
|
||||
if (m_black_can_castle_kingside != other.m_black_can_castle_kingside)
|
||||
return false;
|
||||
|
||||
return turn() == other.turn();
|
||||
}
|
||||
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue