We combine mixed integer linear programming (MILP) and constraint programming (CP) to solve planning and scheduling problems. Tasks are allocated to facilities using MILP and scheduled using CP, and the two are linked via logic-based Benders decomposition. Tasks assigned to a facility may run in parallel subject to resource constraints (cumulative scheduling). We solve minimum cost problems, as...

in this study, a hierarchical hub location problem by considering different modes of transportation and maximum allowed delay is investigated. this study is done on iran’s express postal service with 2 days maximum delay in delivery considering ground and airport hubs. the problem is of the type of location and single allocation for collection, transfer and distribution of the shipments. all th...

Determination of shipment quantity and distribution problem is an important subject in today’s business. This paper describes the inventory/distribution network design. The system addresses a class of distribution network design problem, which is characterized by multiple products family, multiple warehouses and retail-ers. The maximum capacity of vehicles and warehouses are also known. The res...

We study the mixed-integer rounding (MIR) closures of polyhedral sets. The MIR closure of a polyhedral set is equal to its split closure and the associated separation problem is NP-hard. We describe a mixed-integer programming (MIP) model with linear constraints and a non-linear objective for separating an arbitrary point from the MIR closure of a given mixed-integer set. We linearize the objec...

the set covering problem (scp) is a well-known combinatorial optimization problem. this paper investigates development of a local branching approach for the scp. this solution strategy is exact in nature, though it is designed to improve the heuristic behavior of the mixed integer programming solver. the algorithm parameters are tuned by design of experiments approach. the proposed method is te...