mt.cpp

Example on simplest usage of ProgressBar in multithreaded applications

#include <unistd.h>
#include <memory>
#include <vector>
#include <thread>
 
#include "PBar.hpp"
 
void DoSomething()
{
    std::this_thread::sleep_for(std::chrono::milliseconds(10));
}
 
int main()
{
    const unsigned int numberOfThreads = std::thread::hardware_concurrency();
 
    std::cout << "Running this program on " << numberOfThreads << " threads" << std::endl;
 
   std::vector<unsigned long> numberOfCalls;
    unsigned long numberOfIterations = 500*numberOfThreads;
 
    bool isProcessFinished = false;
    
    auto ThrCall = [&](const unsigned int threadNumber)
    {
        for (int i = 0; i < 500; i++)
        {
            DoSomething();
            numberOfCalls[threadNumber]++;
        }
    };
 
    // pbar needs to have it's own thread for it 
    // to be consistent as frequent overwriting on
    // multiple cores leads to interference and 
    // therefore the progress bar is displayed incorrectly
    auto PbarCall = [&]()
    {
        ProgressBar pbarMT = ProgressBar("FANCY", "Multithread");
        while (!isProcessFinished)
        {
         unsigned long sumNumberOfCalls = 0.;
         for (const unsigned long& nCall : numberOfCalls)
         {
            sumNumberOfCalls += nCall;
         }
            pbarMT.Print(static_cast<double>(sumNumberOfCalls)/static_cast<double>(numberOfIterations));
         // note the sleep timer for this lambda function since ProgressBar is running on it's own 
         // thread; otherwise this while cycle will take all resources from the current thread
            std::this_thread::sleep_for(std::chrono::milliseconds(50));
        }
        pbarMT.Fill();
    };
 
    std::thread pbar_thread(PbarCall);
    std::vector<std::thread> thr;
    
    for (unsigned int i = 0; i < numberOfThreads; i++)
    {
      numberOfCalls.push_back(0.);
        thr.push_back(std::thread(ThrCall, i));
    }
    
    while (!thr.empty()) 
    {
        thr.back().join(); 
        thr.pop_back();
    }
 
    isProcessFinished = true;
    pbar_thread.join();
 
    return 0;
}