title: Clusters in Graphviz won't space symmetrically
body: <p>I'm trying to get multiple clusters of nodes to space evenly in Graphviz. </p>
  
  <p>I think the image best explains what I'm trying to do:</p>
  
  <p><img src="https://i.stack.imgur.com/B4bgm.png" alt="enter image description here"></p>
  
  <p>As you can see from the image, there is extra spacing between layers 2 and 3. The space between 2 and 3 should be the same as the space between 1 and 2. </p>
  
  <p>The spacing also needs to scale with more than 3 layers. When I tried more than 3 layers, the 4th layer is spaced as bad as the 3rd layer.</p>
  
  <p>Here is my graph file:</p>
  
  <pre><code>digraph G {
      nodesep=1.25;
      splines=false;
  
      node[width=1, shape=circle];
      edge[style=invis];
  
      subgraph cluster_1 {
          label="Layer 1";
          "1-1" -&gt; "1-2" -&gt; "1-3";
      }
  
      subgraph cluster_2 {
          label="Layer 2";
          "2-1" -&gt; "2-2" -&gt; "2-3";
      }
  
      subgraph cluster_3 {
          label="Layer 3";
          "3-1" -&gt; "3-2" -&gt; "3-3";
      }
  
      edge[style=solid, penwidth=1, constraint=false];
  
      "1-1" -&gt; "2-1";
      "1-3" -&gt; "2-1";
  
      "1-1" -&gt; "2-2";
      "1-2" -&gt; "2-2";
  
      "1-2" -&gt; "2-3";
      "1-3" -&gt; "2-3";
  
      "2-1" -&gt; "3-1";
      "2-3" -&gt; "3-1";
  
      "2-1" -&gt; "3-2";
      "2-2" -&gt; "3-2";
  
      "2-2" -&gt; "3-3";
      "2-3" -&gt; "3-3";
  
  }
  </code></pre>
  
  <p>How can I go about getting my spacing symmetrical? Any help would be much appreciated. Thanks.</p>
  
  <p>Update:
  I have managed to get the spacing even, but it is not a perfect solution.</p>
  
  <p>By placing an invisible node with invisible edges above the graph and connecting it to the top node in each layer, the layers space evenly. However, this node messes up spacing for things that need to be added above the image shown. So, is there a better way to do this?</p>