mcpi/montecarlo_pi.cpp at main · cachevector/mcpi · GitHub

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#include <iostream>
#include <fstream>
#include <random>
#include <cmath>
#include <cstdlib>

int main() {
    const int total_points = 1000000;
    int inside_circle = 0;

    std::ofstream outfile("pi_approximation_data.csv");
    outfile << "Step,ApproxPi\n";

    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_real_distribution<> dis(0.0, 1.0);

    for (int i = 1; i <= total_points; ++i) {
        double x = dis(gen);
        double y = dis(gen);

        if (x * x + y * y <= 1.0) {
            ++inside_circle;
        }

        if (i % 1000 == 0) {
            double pi_estimate = 4.0 * inside_circle / i;
            outfile << i << "," << pi_estimate << "\n";
        }
    }

    double final_pi = 4.0 * inside_circle / total_points;
    std::cout << "Final Approximation of Pi = " << final_pi << std::endl;
    outfile.close();

    // gnuplot script
    std::ofstream gnuplot_script("plot_pi.gp");
    gnuplot_script << "set datafile separator ','\n";
    gnuplot_script << "set title 'Monte Carlo Approximation of Pi'\n";
    gnuplot_script << "set xlabel 'Number of Points'\n";
    gnuplot_script << "set ylabel 'Estimated Pi'\n";
    gnuplot_script << "set grid\n";
    gnuplot_script << "set key left top\n";
    gnuplot_script << "plot 'pi_approximation_data.csv' using 1:2 with lines title 'Approximated Pi', \\\n";
    gnuplot_script << "     3.141592653589793 with lines linestyle 2 title 'Actual Pi'\n";
    gnuplot_script.close();

    // Run gnuplot
    system("gnuplot -p plot_pi.gp");

    return 0;
}