I’m having problems getting the dual variables for a nonlinear problem, with Ipopt as the solver…
I just found this post here of 2015, but not working here and a bit old:
Any updates on the topic?
Have you tried? Works for me:
julia> using JuMP, Ipopt
Feasibility problem with:
* 0 linear constraints
* 0 variables
Solver is Ipopt
julia> @variable(m, 0 <= x <= π / 2)
julia> c = @constraint(m, x >= π / 3)
x >= 1.0471975511965976
julia> @NLobjective(m, Min, sin(x))
This is Ipopt version 3.12.8, running with linear solver mumps.
... lines omitted ...
If you’re having problems, try posting a small reproducible example (How to create a Minimal, Reproducible Example - Help Center - Stack Overflow).
Your example works here as well…
Now I realized that my problem is that Ipopt is letting down while solving the problem…