[SCIP] Accessing GCG from Pyomo package

[Marco Lübbecke]

Hi Abbas, hi list,

(coincdentally! really) we recently started working on the PYOMO/GCG
connection (I forwarded your message, you will be contacted); there
will not be any progress super soon, but you may contribute your
wishes and experience.

-Marco

Am Di., 18. Apr. 2023 um 12:36 Uhr schrieb Abbas Omidi <abb.omidi at gmail.com>:
>
> Dear support team,
>
> First of all, thank you so much for your interesting work to develop PyGCGOpt. I am working on a variant of the parallel machine scheduling problem with the Pyomo package on Google-Colab. By default, everything works well, but when I want to run some moderate problems its default solver, "CBC", cannot execute well. Since I have tried to install SCIP by Pyscipopt package and use the following method to call that.
>>
>> !conda install --channel conda-forge pyscipopt
>> ...
>> SolverFactory('scip').solve(m, tee= True).write()
>
>
> It takes around 4 (mins) to solve the problem optimality. As I have worked with Pygcgopt on Colab, I tried to solve the problem within a separate notebook by calling:
>>
>> m = Model("PMSPPC")
>> m.readProblem("PMSPPC.lp")
>> m.printVersion()
>> m.redirectOutput()
>> m.setMinimize()
>> m.optimize()
>
>
> The problem was solved in seconds!!! (say less than 20 secs and I think in the default mode). Now, I am willing to call GCG from the Pyomo package. To do this I called that by !conda install --channel conda-forge pygcgopttried and the methods like:
>>
>> 1) SolverFactory('scipgcg').solve(m, tee= True).write()
>> 4) SolverFactory('scip-gcg').solve(m, tee= True).write()
>> 2) SolverFactory('gcg').solve(m, tee= True).write()
>> 3) SolverFactory('Pygcgopt ').solve(m, tee= True).write()
>
>
> But, neither of them can be calling the solver and already throw some errors like:
>>
>> RuntimeError: Attempting to use an unavailable solver.
>> The SolverFactory was unable to create the solver "scipgcg"
>> and returned an UnknownSolver object.  This error is raised at the point
>> where the UnknownSolver object was used as if it were valid (by calling
>> method "solve").
>> The original solver was created with the following parameters:
>> executable: scipgcg
>> type: scipgcg
>> _args: ()
>> options: {}
>
>
> I was wondering if, how can I call the GCG within Pyomo?
>
> Best regards
> Abbas
>
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-- 
Prof. Dr. Marco Lübbecke
RWTH Aachen University
Chair of Operations Research
Kackertstrasse 7
D-52072 Aachen
Germany

fon / fax: +49 241 80-93362 / 92369
marco.luebbecke at rwth-aachen.de
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