Sammendrag
We propose a new formulation for the inventory routing problem with an exact solution method, where each customer has an inventory with a maximum holding capacity and a periodic demand. The decision maker has to make sure the customers have enough products in their inventories to satisfy demand in each time period of the planning horizon. Thus, the decision maker must decide which customers to serve in which time periods, how much to deliver of a product once a customer is visited and how to route the fleet of vehicles in order to minimize transportation cost and inventory holding cost. We propose an improved branch-and-cut algorithm combining the current state-of-the-art valid inequalities with a new concept called customer schedules. Customer schedules contain information about delivery periods for each customer and quantity delivered to a given customer in a given period. Preliminary results show that the new algorithm increases the lower bound compared to existing state-of-the-art branch-and-cut methods. A full computational study on how the different valid inequalities impact the lower bounds and solution times will be presented.
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