Setting 'fixed_variable_treatment' IPOPT option not working with SolverFactory

[qtothec]

This is from StackOverflow: https://stackoverflow.com/questions/45807745/setting-ipopt-options-through-pyomo/45840729#45840729

I reproduced the issue running IPOPT 3.12.8 and a branch up to date with master.

This does not work:

from pyomo.environ import *
m = ConcreteModel()
m.x = Var()
m.c = Constraint(expr=m.x >= 2)
m.o = Objective(expr=m.x)
s = SolverFactory('ipopt')
s.options['fixed_variable_treatment'] = 'make_parameter'
s.solve(m, tee=True)

Error is:

ERROR: "[base]\site-packages\pyomo\opt\base\solvers.py", 599, solve
        Solver (asl) returned non-zero return code (1)
ERROR: "[base]\site-packages\pyomo\opt\base\solvers.py", 604, solve
        Solver log:
        Unknown keyword "fixed_variable_treatment"

It does not appear to be directly due to IPOPT, because using the ipopt.opt file strategy from https://www.coin-or.org/Ipopt/documentation/node35.html works.

[ghackebeil]

The default behavior is to send options to Ipopt through the command line, but not all Ipopt options are available through the command line. This is probably one of them. Historically one would place this kind of option in an options file named "ipopt.opt" in the working directory, and Ipopt would pick it up automatically. Very recently I added functionality to the Ipopt interface in Pyomo to write an options file for you. Options that begin with "OF_" will be placed in a temporary options file (with that prefix removed). I don't know if this has made it into a release yet.

[ghackebeil]

@qtothec: Can this ticket be closed? I believe using the "OF_" prefix with your option provides the functionality that you need.

[qtothec]

Yeah, I think it was mainly driven by someone else's StackOverflow question, so if they still have trouble with it, they can open a new ticket.