lastUpdateTimestamp = source.lastUpdateTimestamp;
	public void makeSameAs(UnconditionalValueDerefSet source) {		// Copy value numbers		valueNumberSet.clear();		valueNumberSet.or(source.valueNumberSet);		// Copy dereference locations for each value number		derefLocationSetMap.clear();		for (Map.Entry<ValueNumber, Set<Location>> sourceEntry : source.derefLocationSetMap.entrySet()) {			Set<Location> derefLocationSet = new HashSet<Location>();			derefLocationSet.addAll(sourceEntry.getValue());			derefLocationSetMap.put(sourceEntry.getKey(), derefLocationSet);		}	}