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NNUE Eval ​

This is the adaptation of the NNUE library that I wrote for my chess engine.

init_nnue ​

This function initialises the NNUE network by loading the weights from a specified file. It only needs to be called once at the start of the program.

cpp
void init_nnue(char *filename)
{
    // call NNUE probe lib function
    nnue_init(filename);
}

evaluate_nnue ​

This function evaluates the current board position using the NNUE network. It takes an integer representation of the pieces and the squares and returns an evaluation score. Although I adapted it, I never actually ended up using it in the engine.

cpp
int evaluate_nnue(int player, int *pieces, int *squares)
{
    // call NNUE probe lib function
    return nnue_evaluate(player, pieces, squares);
}

evaluate_fen_nnue ​

This function evaluates a position given in FEN (Forsyth-Edwards Notation) format using the NNUE network. It divides the NNUE's output by 100.0f to convert it to centipawns, which is a common unit for chess evaluation scores, and by 2.0f to adjust the scale of the evaluation as it tends to score around twice as high as Stockfish's evaluations.

cpp
float evaluate_fen_nnue(std::string fen)
{
    return nnue_evaluate_fen((char *)fen.c_str())/200.0f;
}