 It has N nodes, V = {0, 1, ...,N − 1} and the set
of edges "E" = { ("i","j") | "i","j" ∈ "V"}.Given a node "i", we can define its set of neighbors in G by Si(1) = {j ∈ V | (i,j)∈ E}.Let us also consider a scalar field, "h" = {"h"0, .., "h""N"−1} defined on the set of nodes V, so that every node i has a scalar value "h""i" associated to it.