// Computation of PI iteratively
// WRONG version, very slow, too much critical section

#include <stdlib.h>
#include <stdio.h>
#include <omp.h>
static long num_steps = 10000000;
double step;
void main ()
{ 
	int i; double x, pi, sum = 0.0;

	printf("SLOW\n");

	step = 1.0/(double) num_steps;
	// make x private for each thread
	#pragma omp parallel for private(x)
	for (i=0;i< num_steps; i++){
		x = (i+0.5)*step;

		// guard access to sum
		// BUT: TOO OFTEN (every iteration)
		// this will be SLOW
		#pragma omp critical
		sum = sum + 4.0/(1.0+x*x);
	}
	pi = step * sum;
	printf("pi=%lf\n", pi);
}