How to fix error “Solver (ipopt) did not exit normally”?

[liuiloon]

I recently used pyomo to build a optimization model in Python(anaconda) and solve it by solver "MindtPy". This solver worked well until yesterday.But when I made a small change to my model and wanted to solve it again with "MindtPy" today, it showed "Solver (ipopt) did not exit normally".

It seems that there is some problems happened to solver "Ipopt"(Because MindtPy uses Ipopt as its NLP solver). How can I fix it?

Thanks for helping.

[David Bernal]

Hi,

can you share some more details about your problem? It seems like the NLP solver IPOPT failed to solve the subproblems that arise from the MINLP decomposition. Have you tried to solve the continuous relaxation of your problem to see if any of the newer constraints lead to infeasibilities in OPOPT? TO do this, replace 'mindtpy' with 'ipopt' in the solve statement. Notice that this will yield non-integer solutions for your original integer variables but it is a good way of checking you problem beforehand. You can also fix some of the binary variables.