for (int j = 0; j < hs.getTiers().size(); j++)
{
OpenIntObjectHashMap tier = (OpenIntObjectHashMap) hs.getTiers().get(j);
for (int i = 0; i < tier.size(); i++)
{
int key = tier.keys().get(i);
IVertex vertex = (IVertex) tier.get(key);
ITripletValue triplet = SimpleTripletValueFactory.getTripletValue(key);
String vertexFilename = "hss-" + leadingZeros(h, hssLength)
+ "-tier-" + leadingZeros(j, tiersLength)