phi.cpp

#include <iostream>
#include <string>
#include <stdexcept>
#include <chrono> // Für die Zeitmessung
#include <boost/multiprecision/gmp.hpp>

namespace mp = boost::multiprecision;
using high_prec_float = mp::number<mp::gmp_float<0>>;

void print_usage(const char* prog_name) {
    std::cerr << "Benutzung: " << prog_name << " <Anzahl_der_Nachkommastellen>" << std::endl;
}

int main(int argc, char* argv[]) {
    if (argc != 2) {
        print_usage(argv[0]);
        return 1;
    }

    int digits = 0;
    try {
        digits = std::stoi(argv[1]);
        if (digits <= 0) throw std::invalid_argument("Anzahl muss positiv sein.");
    } catch (const std::exception& e) {
        std::cerr << "Fehler: Ungültige Anzahl an Nachkommastellen. Bitte eine positive Zahl angeben." << std::endl;
        print_usage(argv[0]);
        return 1;
    }

    high_prec_float::default_precision(digits * 3.32193 + 16);

    std::cout.precision(digits + 1);

    auto start = std::chrono::high_resolution_clock::now();

    high_prec_float one = 1;
    high_prec_float five = 5;
    high_prec_float phi = (one + mp::sqrt(five)) / 2;

    auto end = std::chrono::high_resolution_clock::now();
    std::chrono::duration<double> duration = end - start;

    std::cout << phi << std::endl;
    std::cerr << "\nBerechnung dauerte " << duration.count() << " Sekunden." << std::endl;

    return 0;
}