for(RyanFeatureVector curr = fv1; curr.next != null; curr = curr.next) {
if(curr.index < 0)
continue;
hm.put(curr.index,hm.get(curr.index)+curr.value);
}
int[] keys = hm.keys();
for(int i = 0; i < keys.length; i++)
sum += Math.pow(hm.get(keys[i]),2.0);
return Math.sqrt(sum);