“…group 4 includes a set of 880 instances introduced in Caserta et al[7]. Such instances are randomly generated with w ∈ {3, 4, 5, 6, 10, 100}, h ∈ {5, 6, ..., 12, 102} and n = w × (h − 2).The 8000 instances of group 5 (Unluyurt and Aydin[29]) are generated with w ∈[3,7], h ∈[4,7] and different densities of the blocks. They can be balanced (b), if the stacks have the same number of stored blocks, or unbalanced (u).In group 6, we consider the 12500 instances described in Zhu et al[39].…”