The computation of the equivalence classes is straightforward: iterating over ρ ∈ R, one checks whether Γ (ρ) is isomorphic to a reaction center Γ ′ previously obtained. If so, ρ is added to set S(Γ ′ ). Otherwise, Γ (ρ) defines a new call and ρ is inserted into the new set S(Γ (ρ)). As a result, we obtain a collection of subsets S(Γ ) of R whose members share a common reaction center Γ .