[SCIP] Accessing GCG from Pyomo package

[Abbas Omidi]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listserv.zib.de/pipermail/scip/attachments/20230418/6fbab35e/attachment.html>