@sascha Sure, since I only have comerical license for 20.1, I guess I have to stick with python 3.8 for now..

is it possible to call the cplex executable by changing the path? It looks like the constraint programming module for docplex could call 20.1.0.0 with this approach

Thank you and @RobPratt!

I see, I will give it a try. I was wondering how can I add the logic that I can make extra orders to fulfill the trackload requirement, probably I can add a slack variable $y = L_f - \sum{v_{cop} x_{cop}}$ and convert it to an order with corresponding items.

@prubin right now I am having a hard time formulate option 2, where extra orders are allowed, but existing orders cannot be split up.

@prubin right, but I am also allowed to make some extra orders to make the trucks full, so I have two options: 1. work only with existing orders and penalize the number of trucks. 2. make extra orders to fulfill the tracks. If the costs of making extra orders are acceptable (compared to options 1). If I can show the cost difference between the two options, I will have a better chance to convince the factory people with my results.

Thank you! what does the superscript "f" in the third constraint mean? isn't $D_c$ contains all the factory for city $c$, and has already being summed over by $k$?

@prubin From the perspective of the factory, less than truckload would pay more, so I want to fill trucks as much as I can.

@PeterD You are right, all products of order i must be produced by a single factory j.

Great, I will use that then, thank you again for your reply!