  The Simple Plant Location Problem with Order (SPLPO) is a variant of the
Simple Plant Location Problem (SPLP), where the customers have preferences over
the facilities which will serve them. In particular, customers define their
preferences by ranking each of the potential facilities. Even though the SPLP
has been widely studied in the literature, the SPLPO has been studied much less
and the size of the instances that can be solved is very limited. In this
paper, we propose a heuristic that uses a Lagrangean relaxation output as a
starting point of a semi-Lagrangean relaxation algorithm to find good feasible
solutions (often the optimal solution). We carry out a computational study to
illustrate the good performance of our method.
