Problem solving with CPLEX on NEOS

[Matteo Nicoli]

Hi everybody,

Trying to run the model in the last few days, setting CPLEX as solver on the NEOS server, I get the following error message (shown after the start of the "Solving" phase).

I am not able to understand the origin of the error. Has anyone seen this error before and know what it is due to?

I suppose there are no errors in my database, since the phases "Reading data files" and "Creating Temoa model instance" work correctly. It seems that something does not work in my pyomo version, but I have made some attempts also with my other databases and everything works normally. In any case, hoping it will be useful I also attach my database.

Thank you in advance,

Matteo Nicoli
______________________________

[    2.50] Reading data files.

[   67.79] Creating Temoa model instance.

[        ] Solving.ERROR: Error parsing NEOS solution file  NEOS log:

Exception found in solve_temoa_instance

Problem executing an event.  No results are available.Problem executing an event.  No results are available.

Exiting Temoa ...

Traceback (most recent call last):

  File "temoa_model\temoa_run.py", line 275, in createAndSolve

    for k in self.solveWithoutMGA():

  File "temoa_model\temoa_run.py", line 247, in solveWithoutMGA

    for k in temoaInstance1.solve_temoa_instance():

  File "temoa_model\temoa_run.py", line 413, in solve_temoa_instance

    raise model_exc

  File "temoa_model\temoa_run.py", line 375, in solve_temoa_instance

    self.result = self.optimizer.solve(self.instance, opt=self.options.solver)

  File "C:\Users\matte\anaconda3\envs\temoa-py3\lib\site-packages\pyomo\opt\parallel\async_solver.py", line 28, in solve

    return self.execute(*args, **kwds)

  File "C:\Users\matte\anaconda3\envs\temoa-py3\lib\site-packages\pyomo\opt\parallel\manager.py", line 111, in execute

    "Problem executing an event.  No results are available.")

pyomo.opt.parallel.manager.ActionManagerError: Problem executing an event.  No results are available.

[Joe]

Hi Matteo,

Yes, I've run into this issue as well. The NEOS administrators now require users to register with them, and jobs must be submitted along with an email address. There's some more information on Stack Overflow here on setting up a Pyomo model with NEOS. You should be able to get it to work with your Temoa instance by registering with NEOS. I'm not sure yet if there's a generic solution, but at some point I plan on contacting the NEOS administrators to see if there's a workaround.

Best,

Joe

[Matteo Nicoli]

Hi Joe,

Thank you very much for your quick response.

Yes, I am aware of this new requirement from NEOS server and I have already updated (some weeks ago) the related files in the packages used to connect to the server.  Indeed, as I told you with other databases everything works correctly: I can connect to the server and I obtain the results.

In other words, I suppose that something peculiar of this specific database causes the connection error to the server but, at the same time, I think that its structure is correct since I do not obtain error messages befor the solution phase begins.

Thank you for your time,

Best,
Matteo Nicoli

[Joe]

Hi Matteo,

In that case, I'm really not sure what's causing the error. I was able to successfully run your database on my machine (see attached screenshot). The NEOS website has this FAQ that describes some of the performance limits. Is it possible that you're hitting the 3GB memory limit per run? I'm not sure what else could be causing NEOS to fail. You could try contacting the system administrators there for more info.

Best,

Joe

[Matteo Nicoli]

Hi Joe,

Regarding our previous conversation, I found the following error message among the output files of the unsuccessful model runs:

JobIn file length exceeds maximum of 16777216

It is an error from NEOS and they say it is due to a limit of 16MB for the input files to the server.

I don't know if the problem can be overcome in some way, I report it here as an update hoping that it will be useful for any developments.

Best,

Matteo Nicoli

[Joe]

Hi Matteo,

Thanks for letting us know. Both CPLEX and Gurobi can be downloaded and installed for free under an academic license. For non-academics, they may also offer limited time licenses for a lower price.

Best,

Joe

[Matteo Nicoli]

Dear Joe,

Thank you very much for the extremely useful suggestion!

In the past few days I have tried to install the free version of CPLEX but without success. I did not know the Gurobi solver and thanks to your indication I was able to install it very easily, being therefore independent from the use of neos. Currently, all works correctly.

I publish this answer hoping it will be useful for any future modelers who have a similar problem.

Again, thanks a lot. I really appreciate your help!

Best,
Matteo

[Joe]

Great to hear Matteo! We've actually found Gurobi to be faster than CPLEX in several of our benchmarking runs.

Best,

Joe