CODEWITHSUNDEEP
pythonmipsgurobi
Lana K
Lana K

Reputation: 1

How do I stop a method if model cannot find a solution within timelimit?

I have a complex MIP model in Python, solve with Gurobi, and long program to run. Usually, I run it and then write the output (values of variables, solution parameters, etc.) to a file. For large instances, the model does not find any solution within the time limit, and then logically gives me an error when I try to retrieve values for variables, which stops the whole code. In this case, I would like it to skip the output section. I tried to achieve this by only writing the output if model.Params.SolutionCount != 0. However, it still gives me the same error of trying to retrieve the variables within the if-statement. Is there any other way to tell Python to skip code if there is no solution without interrupting the program completely? Thank you!

Upvotes: 0

Views: 506

Answers (1)

mattmilten
mattmilten

Reputation: 6726

You should always check the solution status before trying to query solution values. This can be like this:

...
model.optimize()

if model.status == GRB.INF_OR_UNBD:
    # Turn presolve off to determine whether the model is infeasible
    # or unbounded
    model.setParam(GRB.Param.Presolve, 0)
    model.optimize()

if model.status == GRB.OPTIMAL:
    print('Optimal objective: %g' % model.objVal)
    model.write('model.sol')
    sys.exit(0)

elif model.status != GRB.INFEASIBLE:
    print('Optimization was stopped with status %d' % model.status)
    sys.exit(0)

This is taken from the Gurobi documentation.

Upvotes: 0

Related Questions