Pass time limit to Couenne

[Johannes Bethcke]

Hello,

I'm using Pyomo to generate MINLPs and solve them with the MINLP solver Couenne. It would be nice to pass Couenne a time limit when solving an instance. So I tried the following code.

opt = SolverFactory("couenne-0.5.3")
instance = model.create_instance("instance_1.dat")
results = opt.solve(instance, timelimit=10)

The instance solves in less than 10 seconds. Everything runs smoothly. However, if I use timelimit=1, the following error is produced:

pyutilib.common._exceptions.ApplicationError: Solver (asl) did not exit normally

Would you know a workaround? Or should I just pass the timelimit manually to Couenne?

Johannes

[Gabriel Hackebeil]

I believe the better approach would be to set the timelimit using a Couenne option if possible. E.g., assuming the option name is ‘timelimit’,

# persistent option

opt.options[‘timelimit’] = 1

opt.solve(instance)

# or one-time option

opt.solve(instance, options={‘timelimit’: 1})

The ‘timelimit’ keyword for the solve() method is at best implemented by killing the child solver process, which likely won’t result in any candidate solution being stored unless the solver has special signal handling (and I’m not sure what signal we send to the child process).

Gabe

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[Johannes Bethcke]

I tried this before but it seems that the only way to pass a time limit option to Couenne is via a settings file couenne.opt. It has to reside in the same directory as the Couenne executable.

Thanks for your help:)

[Johannes Bethcke]

Okay this indeed seems to be the only way. The problem now is: Pyomo seems to ignore the settings file couenne.opt. When I call Couenne directly from the command prompt this works fine and I can e.g. limit computation time.

One reason I can think of is: Pyomo does call Couenne from different directory than the one where the couenne.opt file reside. Could that be true? Would it be possible to find out that directory. I already checked the path variables on my Windows 10 sytem.

Regards,

Johannes

[Johannes Bethcke]

Got it! The couenne.opt file needs to be in same directory as the python file that is being called to call pyomo. In my case the PyCharm Workspace.

Johannes

[Nesrine]

Hello Johannes,

I am confronted with a similar problem. Trying to pass the time_limit option to couenne, but since I've installed Pyomo through Anaconda, I'm having trouble finding the directory where Pyomo is being called by a python file. 

Any thoughts on this? 

Nesrine