let rec aux tree =
    let i, solutions = match tree with
      | Leaf i -> i,
        [IntSet.empty, 0., infinity, 0., 0.;
         IntSet.singleton i, infinity, 0., 0., 0.]
        |> List.map soln_of_tuple
      | Node (i, subtrees) ->
        let closest_leaf = IntMap.find i cleafm in
        i,
        List.map aux subtrees
          |> combine_solutions ~verbose n_leaves
          |> cull ~verbose ~closest_leaf

    in
    List.iter (csvrow i) solutions;
    if i = top_id then solutions else (* ... *)
    let marks = bubbles_of i
    and masses = IntMap.get i [] mass |> List.enum
    and node_closest_leaf = IntMap.find i cleafm in