C++ Chess Library

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Getting Started ​

chess-library is a single header library.

Thus to use it in your project just copy the header file chess.hpp into your project
and include in the necessary files.

The entire library is behind the chess namespace so for easy usage just say

Example ​

cpp
#include "chess.hpp"

using namespace chess;

That's it!

Also see my examples.

TIP

The library internally uses assert and may print debug information to std::cerr. To disable this define NDEBUG when compiling.

Understanding Bitboards ​

A bitboard is a fundamental data structure in chess programming that uses a 64-bit integer to represent a chess board. Each bit corresponds to one square on the board - when a bit is 1, it means something is present on that square (like a piece or an attack). Bitboards make chess operations very efficient since they can use CPU's native bitwise operations.

For example, to represent a white pawn on e2, you would set the bit at position 12 (counting from 0, starting at a1):

cpp
Bitboard pawn_e2;
pawn_e2.set(12);  // Sets bit for e2 square

You can combine bitboards using bitwise operations:

cpp
Bitboard white_pawns = ...;  // All white pawns
Bitboard black_pawns = ...;  // All black pawns
Bitboard all_pawns = white_pawns | black_pawns;  // Union of both

Bit Position Operations ​

  • lsb() - Returns the index of the Least Significant Bit (first 1 bit from right). This is useful for iterating through pieces on a bitboard, as it finds the "lowest" occupied square. This library uses the layout where the first bit is at index 0 (a1), and the last bit is at index 63 (h8).

  • msb() - Returns the index of the Most Significant Bit (first 1 bit from left). This finds the "highest" occupied square. Rarely used in chess programming.

Bit Counting and Manipulation ​

  • count() - Returns the number of 1 bits in the bitboard. For example, if you have a bitboard representing all pawns, count() would tell you how many pawns are on the board.

  • pop() - Returns and clears the least significant bit. This is particularly useful when you need to process each piece on a bitboard one at a time. Each call to pop() gives you the next piece position and removes it from the bitboard. This approach is much faster than any for loop.

  • getBits() - Returns the raw 64-bit integer underlying the bitboard. This gives you direct access to the underyling 64-bit integer when you need it.