IP model takes too long to solve

Answered

Sander Mertens

January 15, 2023 16:51

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I have a pure integer problem which takes very long to solve (I don't know the exact time, but after times over 12 hours there was still no solution).

The model has a size of:
143,442 rows, 161,547 columns and 3,174,779 nonzeros
Variable types: 0 continuous, 161,547 integer (130,077 binary)

I'm solving it on a computer with the following specs:
CPU model: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz

Is there anything I can do to increase the solving time without modifying the model itself?

Related to

• Performance
• Parameters

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  Jaromił Najman

  • Gurobi Staff

  January 16, 2023 09:12

  Please note that with over 3 million nonzeros, your model is very large and it is expected that it takes a long time to solve or even to find a feasible solution.

  Is there anything I can do to increase the solving time without modifying the model itself?

  You could try experimenting with the most important parameters for MIPs. In particular, you should experiment with the NoRelHeurTime, Heuristics, MIPFocus parameters. If possible, you should provide a MIP start or hints. To make the experimentation efficient, you should work with a smaller data set to have a way smaller model. This will save a lot of time when testing different settings and MIP starts.

  You might also try to improve your formulation and check whether you model has any numerical issues.

  Best regards, 
  Jaromił

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