rIPOPT fails on quad tank dynamic optimization problem

[devin-griff]

Notebook and .nl file attached. This is a toy problem commonly used in the literature. IPOPT solves it in a few iterations.

Quad tank ripopt.zip

[jkitchin]

This should be fixed on the next release. It solves in 12 iterations with my local copy. 🤞 I can finish issue #25 ASAP!

[devin-griff]

Awesome, looking forward to the next release. I will exercise it on some larger problems also.

[jkitchin]

v0.8.0 is now released and solves this on my end:

$ ripopt "Quad tank ripopt/model.nl"
...
Number of Iterations....: 12

Objective...............:    2.3635166628768542e2
Dual infeasibility......:  1.0447318665327284e-11
Constraint violation....:   3.5969378586742096e-9
Complementarity.........:   9.7773394073432639e-9

EXIT: Optimal Solution Found.
ripopt 0.8.0: Optimal after 12 iterations
Total seconds in ripopt = 0.055

The fix came in along with the rest of the v0.8 Ipopt-3.14 alignment work (default backend changed to feral; full set of changes in CHANGELOG.md). Update via:

• Rust crate: cargo install ripopt --version 0.8.0
• pyomo plugin: pip install -U pyomo-ripopt
• Python bindings: pip install -U ripopt

Closing — please reopen if you hit it again on this or any related problem.