#include <iostream>
#include <cmath>
extern "C" {
#include "cblas.h"
}

using namespace::std;

double naive_dnrm2(int n, double *x)
{
	double sum = 0.;
	for (int i = 0; i < n; ++i)
		sum += pow(x[i], 2);
	return sqrt(sum);
}

int main()
{
	double x[3] = {1.354e300, 1.789e200, 8.765e250};
	cout << "cblas_dnrm2" << endl;
	cout << cblas_dnrm2(3, x, 1) << endl;
	cout << "naive_dnrm2" << endl;
	cout << naive_dnrm2(3, x) << endl;
	double y[3] = {1.354e-300, 1.789e-200, 8.765e-250};
	cout << "cblas_dnrm2" << endl;
	cout << cblas_dnrm2(3, y, 1) << endl;
	cout << "naive_dnrm2" << endl;
	cout << naive_dnrm2(3, y) << endl;
	return 0;
}