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I have been using Cplex and docplex (on python) on my PC for a long time and it was working fine. But lately when I run my script it starts the engine but it sticks at the beginning for a very long time (24 hours maybe) and then it terminates the process with no solutions and no error. When I use conflict_refiner same thing happens, it sticks on checking conflicts, it does not finish checking conflicts and it does not return any conflicts. I tested my script on other device and it was working fine. I can not understand the problem. Here are my device info:

Windows: 10
python (anaconda): 3.6.9
Spyder: 3.6
Cplex studio: 12.10.0
docplex :2.15.194

Edit: Current model log_output freezes here:

       Nodes                                         Cuts/
   Node  Left     Objective  IInf  Best Integer    Best Bound    ItCnt     Gap

      0     0        0.0000 72605                      0.0000        7
Sana.Nz
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1 Answers1

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So, you are saying that your Python program started behaving differently, all things being equal?

It is not possible to answer without knowing what exactly is your program doing? It is solving a model? If so did you turn on logging by passing log_output=True, if this is the case, does the log differ?

If your problem has no solution, the conflict refiner may sometimes take very long time. I suggest you try the docplex.mp.Relaxer class, which implements a relaxation algorithm. It usually runs faster, but does not answer the same question. Relaxer tries to minimize slack to make the problem feasible, and shows you which constraints had to be relaxed, and by how much slack.

Philippe Couronne
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  • Yes my program is solving an MIP model using a solution pool. I can't see the log_output when solving with a solution pool. – Sana.Nz Oct 28 '20 at 10:19
  • Try creating the model with keyword argument `log_output=True`, which will be passed to CPLEX before you execute the workaround code for populating the pool. The real good news is, a new DOcplex will be released soon with a direct support for solution pools, so all these issues with workaround code should disappear. I'll keep you posted when 2.16 is out. – Philippe Couronne Oct 28 '20 at 14:08
  • I edited my question and added the log_output result – Sana.Nz Oct 28 '20 at 16:48
  • Could you insert the complete log? – Philippe Couronne Oct 29 '20 at 08:25
  • The last line you sent shows the model is stuck at node 0 with 72605 integer infeasible variables (which is a lot). A few suggestions: set parameters mip.display to 4 to see more, and emphasis.mip to 1 (feasibility) t generate more solutions.. – Philippe Couronne Oct 29 '20 at 09:53