multithread.h

#ifndef MULTITHREAD_H
#define MULTITHREAD_H

#include "video.h"

template <typename Func>
void multiThread(Video &video, Func function) {
    std::vector<std::thread> threads;

    size_t numFrames = video.numFrames;
    // Get number of available threads for this specific device
    size_t hardwareThreads = std::thread::hardware_concurrency();

    // Error condition if return 0, then only try 2 threads
    if (hardwareThreads == 0) {
        hardwareThreads = 2;
    }
    size_t numThreads = std::min(hardwareThreads, numFrames);
    size_t framesPerThread = numFrames / numThreads;
    size_t remainingFrames = numFrames % numThreads;

    int64_t startFrame, endFrame;

    // Calculate the range of frames for the threads and start them
    for (size_t threadIndex = 0; threadIndex < numThreads; threadIndex++) {
        startFrame = threadIndex * framesPerThread;
        endFrame = startFrame + framesPerThread;

        if (threadIndex == numThreads - 1) {
            endFrame += remainingFrames;
        }

        threads.emplace_back(function, startFrame, endFrame);
    }

    // Join all threads when finished so that there are no loose threads
    for (size_t threadIndex = 0; threadIndex < numThreads; threadIndex++) {
        threads[threadIndex].join();
    }
}

#endif  // MULTITHREAD_H