code: private LinkedHashMap<HypergraphNode<Variable>, Integer> createInitialOrdering(final Formula formula, final Map<Variable, HypergraphNode<Variable>> nodes) {
      final LinkedHashMap<HypergraphNode<Variable>, Integer> initialOrdering = new LinkedHashMap<>();
      final List<Variable> dfsOrder = this.dfsOrdering.getOrder(formula);
      for (int i = 0; i < dfsOrder.size(); i++)
        initialOrdering.put(nodes.get(dfsOrder.get(i)), i);
      return initialOrdering;
    }
docs: Creates an initial ordering for the variables based on a DFS.
  @param formula the CNF formula
  @param nodes   the variable to hypergraph node mapping
  @return the initial variable ordering