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Dear AIMMS community group,

I’m currently working on modelling an Inventory Routing Problem in AIMMS based on below model formulation to minimize the total transportation and inventory cost.

I have created a project in AIMMS as enclosed, however despite no errors I don’t receive a solution (solution is total cost of 0).

Therefore, hoping someone can support to have a look at my model and advise on what might be wrong and how to solve to generate the solution.

I’m attaching you my AIMMS project as well as the model formulation that I’m using.

Thanks a lot in advance!

Hi @Lisa, there are several small mistakes in your model:

  • You did not specify an objective (Gesamtkosten_W) in the mathematical program attribute.
  • You should use Lagerendbestand_I(i,t-1) instead of Lagerendbestand_Vorperiode_I0(i,t).
  • The y variable for i=0 is missing. Should i=0 be a depot or a supermarket?
  • Constraint Angebotsrestriktion seems to be missing the z variabe for i=0.

@Marcel Hunting thank you for your feedback! Can you advise how to model I(i,t-1) in AIMMS? If I try to put “t-1” in the index domain, I always receive an error message. So I’m not sure how I can show in AIMMS that I(i,t-1) should reflect the inventory level of the previous period? Thanks in advance!

Hi @Lisa Schmitt, you should use Lagerendbestand_I(i,t-1) in the constraint definition (instead of Lagerendbestand_Vorperiode_I0(i,t)).

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