Exact sequential choice of locations in a network

Medium to large network location problems can often be solved only approximatelywithin reasonable computing time. Standard solution techniques focus on the tentative choiceof locations embedded in an enumerative search. In contrast, the method presented hereselects or rejects facilities conclusively and thus avoids costly backtracking schemes. Itdraws on supermodularity and Lagrangian relaxation. We rank well‐known variable‐fixingtests and propose a hierarchy of tests that provides an attractive time‐accuracy trade‐offwhich we assess computationally.