Algorithm 2. Pseudocode of the k-level hierarchical iterated tabu search algorithm.

k-Level_Hierarchical_Iterated_Tabu_Search procedure;

/ input: p—current solution

/ output: p✩—the best found solution

/ parameter: Q〈k〉—number of iterations of the k-level HITS algorithm

begin

p✩: = p;

for q〈k〉: = 1 to Q〈k〉 do begin

apply k–1-Level_Hierarchical_Iterated_Tabu_Search to p and get p∇;

if z(p∇) < z(p✩) then p✩: = p∇; / the best found solution is memorized

if q〈k〉 < Q〈k〉 then begin

p: = Candidate_Acceptance(p∇, p✩);

apply mutation procedure to p

endif

endfor

end.