[Ipopt] Issue on hardware implementation IPOPT: scaling issue?

Martijn Disse M.W.Disse at student.tudelft.nl
Tue Oct 2 05:35:45 EDT 2012

Hi everyone,

I've build an NMPC controller as a Matlab C-mex S-function and it works like a charm in Simulink. When I however compile to an xPC-target (turn a PC into a dedicated hardware) executable using MSVS 2010 express, I get different results.

I used the "output_file" option on to see what is happening. There are several differences between the Simulink log and the target hardware log:

1. Xpc:  Scaling parameter for objective function = 1.000000e-008
Simulink: Scaling parameter for objective function = 1.163760e-003
2.  Xpc:  compl_inf     = 4.0000000500000000e+005
Simulink:  compl_inf     = 3.4371342722094269e+000
3.  Xpc: overall_error = 4.0000000499999999e-003
Simulink: overall_error = 1.0000000000000000e+002
Iteration 0:
4. Xpc: inf_du lg(mu) = 8.59e-004
Simulink: inf_du lg(mu) = 1.00e+002

It ends up with:
-EXIT: Invalid number in NLP function or derivative detected.
-Restoration phase is called at point that is almost feasible, with constraint violation 5.672143e-007. Abort.
-EXIT: Restoration Failed!

My question: What could case a difference in the hardware implementation (xPC-target, Mathworks) and the Simulink results? The difference is already visible in the completely different scaling values.

I hope someone can help me :)

Best regards,

-Martijn Disse

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