#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/time.h>

#define liczba_watkow 4

pthread_mutex_t lock;
int n=100000;
int nk;
int points;
int nr_watku;


void *losuj(void *i)
{

    int nr_watku2;
        double x,y;
        printf("Startuje watek %d\n",++nr_watku);
        nr_watku2=nr_watku;
        while(points < n)
        {
            int a;
            x = ((double)rand() / (RAND_MAX))*2 - 1;
            y = ((double)rand() / (RAND_MAX))*2 - 1;
            a = x*x + y*y <= 1;
            pthread_mutex_lock(&lock);
            if(a)
                nk++;
            points++;
            pthread_mutex_unlock(&lock);
        }
        printf("Koniec watku %d\n",nr_watku2);
        return NULL;
}


int main()
{
     struct timeval start, end;
     srand(time(NULL));
     double x,y;
     int i,j;
     float s;
     pthread_t w[liczba_watkow];
     nk=0;
     long mtime, seconds, useconds;
     gettimeofday(&start, NULL);
     printf("start:\n");

        for(j=0; j<liczba_watkow; j++)
        {
             pthread_create( &w[j], NULL, losuj, NULL );
        }
        for(j=0; j<liczba_watkow; j++)
        {
             pthread_join( w[j], NULL );
        }




     printf("Liczba pkt. w kole wynosi: %d\n",nk);
     printf("Liczba pkt. w kwadracie wynosi: %d \n",n);
     s = 4. * nk / n;
     printf("Liczba pi wynosi: %f\n",s);

    gettimeofday(&end, NULL);
    seconds  = end.tv_sec  - start.tv_sec;
    useconds = end.tv_usec - start.tv_usec;
    mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5;
    printf("Czas: %ld milliseconds\n", mtime);
    pthread_mutex_destroy(&lock);
     return 0;
}