openmp_thread_pool.cpp

#include "omp.h"
#include <thread>
#include <iostream>
#include <vector>
#include <chrono>


void doNothing(){
    int count =0;
    for (int i=0; i<1000; ++i)
        ++count;
}

int main(){
    int algorithmToRun = 1;
    std::chrono::high_resolution_clock::time_point start;
    std::chrono::high_resolution_clock::time_point end ;
    std::chrono::duration<double> span;

    start = std::chrono::high_resolution_clock::now();
    for(int j=1; j<100000; ++j)
    {
        if(algorithmToRun == 1)
        {
            std::vector<std::thread> threads;
            for(int i=0; i<16; i++)
            {
                threads.emplace_back(std::thread(doNothing));
            }
            for(auto& t : threads) t.join();
        }
        else if(algorithmToRun == 2)
        {
            #pragma omp parallel for num_threads(16)
            for(unsigned i=0; i<16; i++)
            {
                doNothing();
            }
        }
    }
    end = std::chrono::high_resolution_clock::now();
    span = std::chrono::duration_cast<std::chrono::duration<double>>(end - start);
    std::cout << "Time per Iteration: " << (span.count()*1000)<< "ms" << std::endl;
}

Compile:
g++ -fopenmp openmp_thread_pool.cpp -o out

C++ Threads:
91559.7ms
OpenMP Threads:
538.9ms