public static IntSet loadCreation(SerializedMultiFile<int[]> input) throws Exception {
   IntSet output = new IntOpenHashSet();
   for (int i = 0; i < input.getPartitionFunction().getPartitionCount(); i++) {
     IntSet part = new IntOpenHashSet(input.readFirstObject(i));
     output.addAll(part);
   }
   return output;
 }
 public static PropagateBlacklist initialPropagation(
     SerializedMultiFile<int[]> from, SerializedMultiFile<int[]> to) throws Exception {
   PropagateBlacklist pb = new PropagateBlacklist();
   for (int i = 0; i < from.getPartitionFunction().getPartitionCount(); i++) {
     IntList fromList = new IntArrayList(from.readFirstObject(i));
     IntList toList = new IntArrayList(to.readFirstObject(i));
     pb.process(fromList, toList);
   }
   return pb;
 }