Computing the Diameters of Abelian Cayley Digraphs with Degree 2

Suppose that x₁, y₁, x₂ and y₂ are four integers. For a given Cayley digraph Omega=Cay(G, {a, b}), where G=Z²/K, a=(1, 0)+K, b=(0, 1)+K, K=<alpha, beta>, alpha=(x₁, y₂), beta=(x₂, y₂), an algorithm is given to compute the four parameters l, h, m, n of its L-shape tile. Thus the diameter of this Cayley digraph can be calculated by d(Omega)=max{l+h-m-2, l+h-n-2}.