// Computation of PI iteratively
// Basic parallel 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;

	// start the threads, declare sum and x private for
	// each thread
	#pragma omp parallel private(sum, x)
	  {
		// initialize sum (as it is new in each thread)
		sum = 0.0;

		// execute for in parallel
		#pragma omp for
		for (i=0;i< num_steps; i++){
			x = (i+0.5)*step;
			sum = sum + 4.0/(1.0+x*x);
		}

		// guard the access to the updating of shared pi
		#pragma omp critical
		pi += step * sum;

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