aca-tasks/task1/main2.cpp

#include <QRandomGenerator>
#include <random>
#include <fstream>
#include <fmt/format.h>

#include "include/mergesort_mt.h"

//Random generator by Prof. Weber
auto gen_file_input(const std::string &fname) -> void {
    FILE* fp = fopen(fname.c_str(), "w");
    int amount = 1e2;
    int* randNum = (int *)malloc(amount * sizeof(int));
    for(int i = 0; i < amount; i++){
        *(randNum + i) = QRandomGenerator::global()->generate();
        fprintf(fp, "%d\n", *(randNum + i));
    }
}

template<typename T>
auto parse_file(std::ifstream &stream, std::vector<T> &vec) -> void {
    std::string buf;
    T convbuf;

    while (std::getline(stream, buf)) {
        convbuf = static_cast<T>(std::stoul(buf));
        vec.emplace_back(std::move(convbuf));
    }
}

int main(int argc, char *argv[])
{
    const std::string fname = "b1-7_input.data";
    //Generate file first using Qt random generator
    gen_file_input(fname);
    try {
        std::ifstream file(fname.c_str(), std::ios_base::in);
        if (!file.is_open()) {
            fmt::print("\nError opening file");
            return -1;
        }

        fmt::print("\nOpened file {} sucessfully", fname);
        std::vector<int32_t> dataset;

        parse_file(file, dataset);
        fmt::print("\nRead {} values from {}", dataset.size(), fname);

        auto dataset_par = dataset;
        auto dataset_seq = dataset;

        auto t1 = std::chrono::high_resolution_clock::now();
        MergeSorterMT<int32_t> msst([](int32_t a, int32_t b) {
            return (a > b);
        }, 0);
        msst.sort(dataset_seq);
        auto t2 = std::chrono::high_resolution_clock::now();

        auto t_seq = std::chrono::duration_cast<std::chrono::milliseconds>(t2 - t1);
        fmt::print("\nSorted {} entries within {} ms in sequential", dataset_seq.size(), t_seq.count());


        const int threads = std::thread::hardware_concurrency();
        const int max_depth = std::sqrt(threads);

        t1 = std::chrono::high_resolution_clock::now();
        MergeSorterMT<int32_t> msmt([](int32_t a, int32_t b) {
            return (a > b);
        }, max_depth);
        msmt.sort(dataset_par);
        t2 = std::chrono::high_resolution_clock::now();

        auto t_par = std::chrono::duration_cast<std::chrono::milliseconds>(t2 - t1);
        fmt::print("\nSorted {} entries within {} ms in parallel on a system having {} threads and a recursion depth of {}"
                   "\nresulting in a total count of {} threads",
                   dataset_seq.size(), t_par.count(), threads, max_depth, std::pow(2, max_depth));

        auto eq = (dataset_seq == dataset_par);
        fmt::print("\nCheck whether sorted arrays are equal: {}", (eq) ? "Equal" : "not equal");

        fmt::print("\n\n------------Summary------------");
        fmt::print("\nt_seq   = {: > 5.2f} ms", static_cast<float>(t_seq.count()));
        fmt::print("\nt_par   = {: > 5.2f} ms", static_cast<float>(t_par.count()));
        fmt::print("\nspeedup = {: > 5.2f}", (1.0 * t_seq / t_par));
        fmt::print("\nDelta_t = {: > 5.2f} ms", static_cast<float>(t_seq.count() - t_par.count()));
        fmt::print("\n-------------------------------");

        std::ofstream ofile("dataset.out.dat", std::ios_base::out);
        if (!ofile.is_open()) {
            fmt::print("\nError writing to file");
            return -1;
        }

        for (auto &element: dataset_seq) {
            ofile << std::to_string(element) << '\n';
        }

        file.close();
        ofile.flush();
        ofile.close();

        fmt::print("\nWritten to output file");

        return 0;

    } catch (std::exception &e) {
        fmt::print("\nError occured: {}", e.what());
        return -1;
    }
}