#include <stdio.h>
#include <time.h>
#include <omp.h>

long long num_steps = 1000000000;
double step;

int main(int argc, char* argv[])
{
	clock_t start, stop;
	volatile double x;
	double pi, sum = 0.0, tab[40];
	int i;
	step = 1. / (double)num_steps;
	start = clock();
#pragma omp parallel
	{ int id = omp_get_thread_num();
	tab[id] = 0;
#pragma omp for reduction(+:sum)
	for (i = 0; i < num_steps; i++)
	{
		x = (i + .5)*step;
		tab[id] += 4.0 / (1. + x*x);
	}
#pragma atomic
	sum += tab[id];
	}

	pi = sum*step;
	stop = clock();

	printf("Wartosc liczby PI wynosi %15.12fn", pi);
	printf("Czas przetwarzania wynosi %f sekundn", ((double)(stop - start) / 1000.0));
	return 0;
}