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My optimisation experiment inside AnyLogic is refusing the run, the error coming up is:

Internal OptQuest Error. (Is Feasible() - solution has not been evaluated.)

I cannot find anyone online explaining what this means and so I was wondering if anyone here could help?

Any help would be appreciated

Natasha Jones
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  • Have you tried deactivating any constraints and requirements, if you used any? – Benjamin Apr 17 '21 at 14:35
  • Hi Benjamin, When I disable the requirement I have set it also generates the same error – Natasha Jones Apr 17 '21 at 18:26
  • Afraid there wont be a solution but to re-trace your steps until the error does not appear anymore. Hope you have versioned your model and can go back in time ;) – Benjamin Apr 18 '21 at 17:07
  • I mean I am following a webinar exactly and I have re-created the entire file multiple times and am still getting the same error so that doesn't seam to be the case – Natasha Jones Apr 18 '21 at 22:13
  • Might be an older version of AnyLogic... – Benjamin Apr 19 '21 at 04:10
  • Same problem, the latest version of AnyLogic and professional version. I submitted it to AnyLogic support. I will update here if I get any updates. – Jaco-Ben Vosloo Mar 14 '22 at 11:50

3 Answers3

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AnyLogic support confirmed this as a bug

"The error occurs if the number of iterations is less than the number of CPU cores available for parallel evaluations. " They will fix it in one of the next AnyLogic updates. Currently, the error can be avoided as follows:

  • disable parallel evaluations in the properties of the experiment (Which is not great as it slows down your execution considerably)

or

(Preferred)

  • reduce the number of available CPU cores in AnyLogic Preferences (Tools > Preferences... > Runtime).

I have 4 physical cors and 8 virtual cores. When I changed this to 4 it works fine, anything above it gives the error randomly.

Jaco-Ben Vosloo
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IsFeasible() is called by OptQuest engine on a best found solution to make sure it satisfies constraints, from memory this error usually means that no solution has been found. Can you try running one of the example models that has an Optimization experiment (like 'Supply Chain' for example) just to check that your AnyLogic is set up correctly and optimization is working. If it does then I am afraid there is an error in your model that prevents generation of solutions.

Artem P.
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  • Yes I have run example documents downloaded from the internet and the optimization of them has worked. I understand that it must be an issue with my simulation however I am following a AnyLogic webinar for delivery fleet optimization and so it is very confusing to me what I could have done wrong – Natasha Jones Apr 19 '21 at 13:55
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Had exactly the same problem, I think we were doing the same example from the webinar. Go to Optimization properties > Advanced and uncheck "Allow parallel evaluations" (my program is in Spanish, so it may have different wording, I've just translated it).

I still don't know why there was a problem, maybe it is because with a student license you can't run parallel simulations, but it solved it for me.

Dharman
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Manuel
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  • I just ran into the same problem, with a completely different solution and I have the professional version - it makes no difference. I think it is an issue with multithreading. – Jaco-Ben Vosloo Mar 14 '22 at 11:49