As a next step, we rank these candidate bases and take again the top t of them. To this end, for each M ∈ C we define the score function score(M ) := q∈Q ϕ δ (M q) , and let M be the subset of C containing the top t basis according to their value score(M ). As mentioned above, each M ∈ M induces a the set V q (M ) := {v q := round(M q) : q ∈ Qf } ⊂ Z 3 , of possible Miller indices for Q that we can used as targets for our robust optimization.