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If backtracking is performed, then some constraints on the most promis-
ing region are relaxed. For the IHLP, by dropping some cuts that let certain
hub(s) open, the next most promising region will include the current most
promising region and the best sample obtained so far. The algorithm usu-
ally stops when the computational resource (e.g., time) reaches a predened
value. Other problem-depend stopping criteria can also be designed.
5.3.3 Computational Results
In Pi et al. (2008), 21 randomly generated cases were tested. The solutions
generated by the HNP–MP approach were compared to those computed ...