Starting from a (partial) AAM α, a (partial) ITS is readily constructed in linear time. In practice, one can start with an edgeless graph comprising the vertices of G endowed with the double labels (a G (x), a H (α(x))) for all x ∈ V (G) and insert edges by iterating over the edge lists of G and H, at the same time recording the edge labels, see also. In the same manner, the reaction center Γ can be obtained directly from the (partial) AAM restricted to the reaction vertices, inserting reaction edges only.