OpenMP on Qt-based app

Max Rafiandy

I code for a benchmark tool. While benchmark executed, it use all processor resources (all threads) using OpenMP library to gain the performance peak of processor. For a non-Qt app and compiled the program by gcc -fopenmp -obenchmark foo.c
it works fine, runs on CLI without any Qt library. However, if I use Qt to design its GUI, the #pragma parallel region won't creating multiple task even if omp_set_num_threads(value) were set.

#include <QApplication>
#include <QQmlApplicationEngine>
#include <pcm/cpucounters.h>
#include <omp.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
    std::cout << "Max Thread " << omp_get_max_threads() << std::endl;
    omp_set_num_threads(omp_get_max_threads());
    #pragma omp parallel
    {
        int tid = omp_get_thread_num();
        printf("Hello Qt Parallel %d\n",tid);
    }

    QApplication app(argc, argv);
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

Actually, this is not my benchmark code. It just a simple code to make sure that the parallel region runs multiple threads or not. The question is: how to use OpenMP thread on Qt-based app?

Best Regard

Max Rafiandy

Solved. The problem was my mistake :)
The .pro file needs to set both QMAKE_CXXFLAGS += -fopenmp and QMAKE_LFLAGS += -fopenmp. I just added the QMAKE_LFLAGS += -fopenmp before.