Infeasible Solution in my Thesis model

  • 16 August 2019
  • 5 replies
  • 215 views

Hello,

trying to solve my Thesis Model there has been message about infeasible solution. ''Warning: After zero iterations CPLEX 12.8 concluded that an integer solution to MeanCostPlan4 does not exist.''

the model is about my thesis, so i would appreciate some help. i attach a zipped file(Fdata1 is the data file i use) & the excell for the extra data for Section4.

More details about the Model:
  • The problem is in section4. when i run the Mp of section3 i find a solution, but with the data of Section4, infeasibility
  • We use a network of 10Nodes. starting node=i & end node=j. We want to have 2 hubs one from S=Pre-istalled nodes(1-7) & one from T=install new Hub(8-10)
  • we want the whole flow to pass throught the Hubs S&T so i create the variable Z(i,j,s,t)
  • In section1 is the main model, in section2 The installation cost, in section3 constraints about the capacity of the nodes and in Section4 Constraints about thn minimum flow from each node i to eacg hub S&T

5 replies

Userlevel 3
Your AIMMS model is missing a procedure to load the data from the Excel file. It is also missing solve statements. Please add those and upload your project again.

Please note that math programs MeanCostPlan2, MeancostPlan3 and MeanCostPlan4 are exactly the same because they use the same set of variables and constraints (namely AllVariables and AllConstraints respectively), and the objective variable and optimization direction are also the same.
Marcel,

Thank u for the straight rensponse.
I fixed and i sent u back the model. The new file for the data is Fdata2.
Userlevel 3
The constraint SConstraint(i,s) has definition

code:
OutgoingDemS(i,s) + IncomingDemS(i,s) >= MinimFlowS(i,s)*Xs(s)

The data of the parameters OutgoingDemS and IncomingDemS is empty, and therefore this constraint enforces Xs(s) to be 0, which results in an infeasibility.

You have defined the parameter OutgoingDemS as

code:
sum[(j,t), DemandFlow(i,j)*Z(i, j, s, t)]

Here Z is a variable. I think that you should change OutgoingDemS into a variable. Same for IncomingDemS.
Hello Marcel,
Thank u very much for your notifications. They were really usefull.

One more question. I would like math programs MeanCostPlan2, MeancostPlan3 and MeanCostPlan4 to express only the contraints of theiw section. How i change that?
Userlevel 3
For MeanCostPlan2 you can create the following set:

code:
Set ConstraintSet2 {
SubsetOf: AllConstraints;
Definition: AllConstraints * Section_2;
}

You should use this set in the Constraints attribute of the math program (instead of AllConstraints).

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