Instances for the Flexible Multi-Period Multi-Depot Capacitated Vehicle Routing Problem with Time Windows

The FMPMD-CVRP-TW instances are adapted from the classical periodic vehicle-routing (PVRP) benchmark data, and are stated here for a Flexible Multi-Period Multi-Depot Capacitated Vehicle Routing Problem with Time Windows. Each instance describes a network of two depots and n customers served over a planning horizon of T days. Depot 1 coincides with node 0 of the customer graph, so the first row of the depot-to-node distance matrix reproduces row 0 of the node-to-node matrix; depot 2 is a distinct location, present only through its own row of distances, and its distance to depot 1 is fixed at 50 in every instance. Demand is flexible rather than fixed: each customer carries a nominal demand W_i and may be served any quantity inside the interval [wmin_i, wmax_i], set throughout at [0.25 W_i, 0.75 W_i]. The visit interval duedate_i inherited from the source PVRP data (2, 4, 6 or 12 days) is retained in the files but is not binding under the single-visit model; it is what generates the spread of nominal demands, since a customer visited less often accumulates more between visits.