![]() upon re-reading the above declarations, some improvements come to mind- if the class already stores a list of moves, I should have just returned pointers to the same in getMoveList and getCaptureMoveList for additional efficiency. checks are disregarded which require knowing the broader game state - those are delegated to the chess board). Quasilegal moves are defined as those within the move rules of the piece, disregarding for now whether the player would e.g. Moreover, only those moves resulting in a capture of an opponents piece can be generated, for reasons that will become clear in a bit when we cover quiescence searches. directly).Įach piece can generate a set of quasilegal moves given the current chess board state which is implemented differently for each piece type. The chess board is hence declared as an 8x8-Array containing pointers to this generic Piece (and not a Pawn, Bishop etc. Hence, we have the following classes: Pawn, Knight, Bishop, Rook, Queen, Knight - as well as a " generic" Piece-class from which all of these are inherited. The colour (an enum type, black/white).the horizontal and vertical sliding for rooks) The move generation routine (a method that encodes the move-rules for each piece, e.g.The Piecesįor each chess piece, a class is written which encodes e.g.: pieces and the board itself, as classes whose instances are stored in memory. Here, I followed a much simpler and less efficient, but more readily understandable approach in the context of Object Oriented Programming: Namely, the idea is to represent the objects of the game, i.e. ![]() Several grid based games are amenable to this approach, Connect 4 being one example I may cover at another time. The goal is to minimize the clock cycles per move and hence maximize the considered moves per second. Move generation and execution can hence be handled via sequences of extremely fast bitwise operations (AND, OR, NOT, XOR, et cetera) which are executed within the CPU registers directly, requiring few clock cycles and low memory delays. Now, modern, strong engines use bitboards, which essentially represents the board as a set of 64-bit integers (8x8 bits), where a "1" would indicate that a piece is present, and a "0" would indicate the opposite. How do you encode the chess board and it's pieces? The answer to these questions dictates how moves are generated and executed, and hence massively influences the performance of any engine (which has to cycle through millions of moves to find one it deems optimal). The board representation is the principal prerequisite of any engine. Initial Caveats on Representation of the Board and its Pieces move pieces, reset the board, or make the engine perform a move: Text-based command line inputs are taken to e.g. The algorithm to draw the board is straightforward: Iterate through the board and write characters to the console depending on which piece is present. The chess board is simply displayed via characters on the console, with background coloring to aid in distinguishing the pieces. The InterfaceĪs most things in the coding space do, the chess engine started as a command line based program. ![]() Gamechanger or - for more classical algorithms - the architecture of Stockfish. Readers with a deep knowledge of coding and/or chess will likely not be exposed to new information here and could instead look at excellent, much more advanced resources, e.g. The article is aimed at readers who have no familiarity with computer chess whatsoever. The entire code is available on GitHub, and its general principles shall be covered here without going into too much detail. The result is very crude (by virtue of the facts that I am a complete chess novice and that several improvements to the codebase can be made), but it was nonetheless a fun little project I would like to share. ![]() Out of nostalgia, I redid this project last year and used the opportunity to familiarize myself more with C++. The program implemented the rules of chess and also allowed the player to challenge a computer opponent. Something that was unfortunately lost in time is a chess program I had originally written many years ago in Pascal. Update April 04, 2021: A follow-up to this article can be found here.
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