Skip to main content

Checking feasibility of the problem

Ongoing
Andrey Kihtenko
Gurobi-versary
Conversationalist
First Question

Hello!

I'm sure that my problem is infeasible, but the solver has been trying to find a feasible solution for a long time. Are there any methods to determine whether the problem is feasible or not?

 

Best regards,

Andrey

0

Comments

5 comments

Date Votes
  • Official comment
    Yuriy Zinchenko
    Gurobi Staff Gurobi Staff

    Hello again, Andrey.

    Thank you again for asking an interesting Q.  The problem instance you have shared is small, but is seemingly tough to determine feasibility.  Our apologies for not replying sooner as we have missed your earlier reply.

    I have a couple of questions.

    1. Why do you think the model is infeasible?

    2. How long have you ran Gurobi so far on this model (and what kind of a machine was used)?

    3. Can you say a few words about where the model is coming from?  Looking at the LP file, I am wondering what kind of an application is it for, and whether this info may be exploited to facilitate the numerics.  Namely, we can start with x, y, rotate and check variables.  What do they represent?

    Finally, can you please tell us what is your academic affiliation? 

    Please advise,

     

  • Maliheh Aramon
    Gurobi Staff Gurobi Staff

    Hi Andrey, 

    Can you compute the IIS by calling the computeIIS() method on your infeasible model? Or you get the message that "IIS cannot be computed on a feasible model"? Would you be able to share your model with us through Google Drive, OneDrive, or Dropbox?

    Best regards,

    Maliheh

    0
  • Andrey Kihtenko
    Gurobi-versary
    Conversationalist
    First Question

    Thank you!

    I tried to compute IIS, but it also didn't help. In the case of model.optimize(), the solver has been trying to find a solution for a long time and went through different branches in the log without the status that the model was infeasible :( Can I attach my code (file .py) with the infeasible problem? It's pretty short and I can attach the MPS file as well.

     

    Best regards,

    Andrey

     

    0
  • Maliheh Aramon
    Gurobi Staff Gurobi Staff

    You cannot attach files to the community post. You need to share the Python and the MPS files with us using a link. For example, upload the Python and the MPS files to your Google Drive and then post the link here.

    Best regards,

    Maliheh

    0
  • Andrey Kihtenko
    Gurobi-versary
    Conversationalist
    First Question

    Hi, Maliheh!

    This is the link to my Google Drive with two files: Python code and MPS file:

    https://drive.google.com/drive/folders/1E7N2dKPpnzJVNfA9KOkugJTJmu7PKrn4?usp=sharing

    The problem is infeasible, but the solver can't determine it in a reasonable time. I would be grateful for your help :)

     

    Best regards,

    Andrey

     

    0

Please sign in to leave a comment.

Didn't find what you were looking for?

New post