cmake-openmp-app/main.cpp at main · JayTwoLab/cmake-openmp-app · GitHub

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#include <iostream>
#include <string>
#include <vector>

#ifdef _OPENMP
    #include <opencv2/opencv.hpp>
    #include <omp.h>
#endif

void printOpenMPInfo();

int main() {

    printOpenMPInfo();
    std::cout << std::endl;

    std::cout << "=== OpenMP Info ===" << std::endl;
    std::cout << "Max threads: " << omp_get_max_threads() << std::endl;

    // 4K Image
    cv::Mat image(2160, 3840, CV_8UC3, cv::Scalar(0, 255, 0));
    cv::Mat gray_image(image.rows, image.cols, CV_8U);

    std::cout << "\nParallel processing start..." << std::endl;
    double start_time = omp_get_wtime();

    #pragma omp parallel for
    for (int r = 0; r < image.rows; ++r) {
        if (r % 500 == 0) {
            #pragma omp critical
            {
                std::cout << "Row " << r << " - Thread ID: " << omp_get_thread_num() << std::endl;
            }
        }

        const cv::Vec3b* ptr_in = image.ptr<cv::Vec3b>(r);
        uchar* ptr_out = gray_image.ptr<uchar>(r);

        for (int c = 0; c < image.cols; ++c) {
            ptr_out[c] = static_cast<uchar>(0.299 * ptr_in[c][2] + 0.587 * ptr_in[c][1] + 0.114 * ptr_in[c][0]);
        }
    }

    double end_time = omp_get_wtime();
    std::cout << "Processing done! Time: " << (end_time - start_time) << " seconds" << std::endl;
    std::cout << "Result channels: " << gray_image.channels() << std::endl;

    return 0;
}

void printOpenMPInfo() {
#ifdef _OPENMP
    long value = _OPENMP;
    std::string versionStr = "Unknown Version";

    // OpenMP specification mapping (MSVC Experimental value included)
    if (value == 200505)      versionStr = "2.5";
    else if (value == 200805) versionStr = "3.0";
    else if (value == 201107) versionStr = "3.1";
    else if (value == 201307) versionStr = "4.0";
    else if (value == 201511) versionStr = "4.5";
    else if (value == 201811) versionStr = "5.0";
    else if (value == 202011) versionStr = "5.1";
    else if (value == 202111) versionStr = "5.2";
    else if (value == 202311) versionStr = "6.0 (Preview or Final)";
    else if (value == 2019)   versionStr = "3.1 ~ 4.5 (MSVC Experimental SIMD/LLVM)";

    std::cout << "OpenMP is enabled.\n";
    std::cout << "Constant value (_OPENMP): " << value << "\n";
    std::cout << "Supported OpenMP version: " << versionStr << "\n";
#else
    std::cout << "OpenMP is not enabled.\n";
#endif
}