How to save parameters in the search path (PSO)

[yezhengli-Mr9]

How to save save parameters in the search path (PSO)? Even use

mutable std::mutex file_mutex;

int tscall::write_to_file(std::string content) const {
    std::lock_guard<std::mutex> lock(file_mutex);  // Locking to prevent race condition
    std::ofstream file(filename, std::ios::app);   // Open in append mode
    if (file.is_open()) {
        file << content << std::endl;
    } else {
        std::cerr << "Error opening file!" << std::endl;
    }
}    

pagmo2/src/problems/rosenbrock.cpp

Lines 51 to 59 in ac7b6d2

	/// Fitness computation
	/**
	* Computes the fitness for this UDP.
	*
	* @param x the decision vector.
	*
	* @return the fitness of \p x.
	*/
	vector_double rosenbrock::fitness(const vector_double &x) const

not quite work -- abstract class, template methods, seems many consequential blocks for cmake --build ..