NAR - 1 i 2

#include <string>
#include <iostream>
#include <thread>
#include <math.h>
#include <chrono>
#include <stdlib.h>     /* srand, rand */
#include <time.h>       /* time */
typedef std::chrono::high_resolution_clock Clock;

using namespace std;

class Timer
{
public:
    Timer() : beg_(clock_::now()) {}
    void reset() { beg_ = clock_::now(); }
    double elapsed() const {
        return std::chrono::duration_cast<std::chrono::microseconds>
            (clock_::now() - beg_).count();
    }

private:
    typedef std::chrono::high_resolution_clock clock_;
    typedef std::chrono::duration<double, std::ratio<1> > second_;
    std::chrono::time_point<clock_> beg_;
};

long Prosti(int n)
{
    int count=0;
    long a = 2;
    while(count<n)
    {
        long b = 2;
        int prime = 1;// to check if found a prime
        while(b * b <= a)
        {
            if(a % b == 0)
            {
                prime = 0;
                break;
            }
            b++;
        }
        if(prime > 0)
        count++;
        a++;
    }
    return (--a);
}

void sporo(int n, int br)
{
    cout << "thread T" << br << " started" << endl;
    long x = Prosti(n);
    cout << "thread T" << br << " ended with: " << x << endl;
}

int main(int argc, char* argv[])
{
    int threadNumber = 2;
    if( argc >= 2){
        threadNumber = atoi(argv[1]);
        if( threadNumber < 1 || threadNumber >64 ) return 0;
        cout << "Zeljeni broj threadova: " << threadNumber << endl;
    }
    int n = 5000;
    if( argc >= 3){
        n = atoi(argv[2]);
        if( n < 1) return 0;
        cout << "Zeljeni prosti broj: " << n << endl;
    }
    double t1, t2;
    double r1, r2;
    Timer tmr;
    thread p[128];

// sekvencijalna izvedba X threadova

    t1 = tmr.elapsed();
    cout << endl << "Prvo vrijeme: " << t1 << endl;
    for( int z = 0; z < threadNumber; z++){
        p[z] = std::thread(sporo, std::ref(n), z);
        p[z].join();
    }
    t2 = tmr.elapsed();
    cout << "Drugo vrijeme: " << t2 << endl;
    std::cout << "SEKVENCIJALNO: Proteklo vrijeme (razlika T2-T1): " << t2-t1 << std::endl;
    r1 = t2-t1;
// paralelna izvedba X threadova

    t1 = tmr.elapsed();
    cout << endl << "Prvo vrijeme: " << t1 << endl;
    for( int z = threadNumber; z < threadNumber*2; z++){
        p[z] = std::thread(sporo, std::ref(n), z);
    }

    for( int z = threadNumber; z < threadNumber*2; z++){
        p[z].join();
    }
    t2 = tmr.elapsed();
    cout << "Drugo vrijeme: " << t2 << endl;
    std::cout << "PARALELNO: Proteklo vrijeme (razlika T2-T1): " << t2-t1 << std::endl;
    r2 = t2-t1;
// Izvjesce:
    cout << endl << endl << "Paralelno je brze, i to za: " << r1-r2 << endl;
    cout << "Sto iznosi: " << (int) ((r2/r1)*100) << "%" << endl;
    cout << "Broj threadova: " << threadNumber << endl;
    cout << "Racunajuci prosti broj: " << n << endl;

}