The Big Programming Thread - Page 177

#include <vector>
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <ctime>
#include <chrono>
#include <ppl.h>
#include <concurrent_vector.h>
int main()
{
    std::chrono::time_point<std::chrono::system_clock> TimeStart;
std::chrono::time_point<std::chrono::system_clock> TimeEnd;

	concurrency::concurrent_vector<int> primes;
	primes.push_back(2);

	TimeStart = std::chrono::system_clock::now();

	int Start = 3;
	int Stop = 4000000;
	int Step = 2;

	// Comment out the multi-threaded version and uncomment the single threaded version to see the difference
	/// Multi-Threaded version
	Concurrency::parallel_for(Start,Stop, Step, [&primes](int n)
	{
		auto prime = true;
		int stop = sqrt(n);

		for(auto j=2;j<stop;j++)
		{
			if(n%j==0)
			{
				prime = false;
				break;
			}
		}
	
		if(prime)
			primes.push_back(n);
	});

	TimeEnd = std::chrono::system_clock::now();
	auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(TimeEnd-TimeStart).count();
	auto seconds = std::chrono::duration_cast<std::chrono::seconds>(TimeEnd-TimeStart).count();
	std::cout << "Milliseconds : "<< millis << std::endl;
	std::cout << "Seconds      : "<< seconds << std::endl;
	return 0;
}