vector-resize-vs-push_back.cpp

#include <iostream>
#include <string>
#include <vector>
#include <random>
#include <chrono>
#include <ctime>

int main()
{
    int start_c = 10000, end_c = 20000;

    std::random_device rd;
    std::mt19937 mt(rd());
    std::uniform_real_distribution<double> dist(1.0, 10.0);
    std::chrono::time_point<std::chrono::system_clock> start, end;
    double total_b = 0.0, total_c = 0.0;

    double value = dist(mt);

    for (int size = start_c; size < end_c; ++size)
    {
        std::vector<double> b, c;

        start = std::chrono::system_clock::now();
        b.resize(size);
        for (int i = 0; i < size; ++i)
            b[i] = value;
        end = std::chrono::system_clock::now();
        std::chrono::duration<double> elapsed_seconds = end - start;
        total_b += elapsed_seconds.count();

        start = std::chrono::system_clock::now();
        for (int i = 0; i < size; ++i)
            c.push_back(value);
        end = std::chrono::system_clock::now();
        elapsed_seconds = end - start;
        total_c += elapsed_seconds.count();
    }

    std::cout << std::fixed << "elapsed time average resize\t: " << total_b / (end_c - start_c) << "s\n";
    std::cout << "elapsed time average push_back\t: " << total_c / (end_c - start_c) << "s\n";
}