@Override
public int compare(DataInputView source1, DataInputView source2) throws IOException {
final long diff = source1.readLong() - source2.readLong();
return diff < 0 ? -1 : diff > 0 ? 1 : 0;
}
@Override
public void readWithKeyDenormalization(VertexWithRank record, DataInputView source)
throws IOException {
record.setVertexID(source.readLong() + Long.MIN_VALUE);
record.setRank(source.readDouble());
}