// Computation of PI iteratively
// Reduction operation version

#include <stdlib.h>
#include <stdio.h>
#include <omp.h>
static long num_steps = 10000000;
double step;
void main ()
{ 
	int i; double x, pi = 0.0, sum = 0.0;
	step = 1.0/(double) num_steps;
	  {
		// define x private, make sum reduce the local copies
		// to a global one
		#pragma omp parallel for private(x) reduction(+:sum)
		for (i=0;i< num_steps; i++){
			x = (i+0.5)*step;
			sum = sum + 4.0/(1.0+x*x);
		}

		pi = step * sum;

	  }
	printf("pi=%lf\n", pi);
}