“…As introduced above, it is NP-hard to find an optimal solution or even to give a constant-factor approximation to the unsplittable flow problem. Thus, the literature investigated various randomized search procedures such as genetic algorithms (Cox, 1991;Masri et al, 2019), tabu search (Anderson et al, 1993;Laguna and Glover, 1993;Xu et al, 1997), local search and GRASP (Santos et al, 2013b(Santos et al, ,a, 2010Alvelos and Valério de Carvalho, 2007;Masri et al, 2015Masri et al, , 2019 or ant colony optimization (Li et al, 2010;Masri et al, 2011). One of the major difficulties encountered when solving the unsplittable flow problem with a meta-heuristic is to efficiently create useful paths for the commodities.…”