omp_pi

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

long long num_steps = 1000000000;
double step;

int main(int argc, char* argv[])
{
    double start, stop;
    double x, pi, sum=0.0;
    int i;
    step = 1./(double)num_steps;
    start = omp_get_wtime();

    omp_set_num_threads(5);

#pragma omp parallel
    {

#pragma omp for reduction(+:sum) private(x) schedule(guided)
        for (i=0; i<num_steps; i++)
        {
            x = (i + .5)*step;
            sum = sum + 4.0/(1.+ x*x);
        }

    }

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

    printf("The value of PI is %15.12f\n",pi);
    printf("The time to calculate PI was %.2lf seconds\n",stop - start);

    return 0;
}