[Ipopt] question about complementarities constraints

Andreas Waechter andreasw at watson.ibm.com
Wed Sep 9 14:23:54 EDT 2009

Hi Laure,

> I am an user of Ipopt on NEOS and I specially use complementarity constraints.
> I appreciate the good results Ipopt can furnish.

Thanks, it's great to hear this.

> I have read on your wiki that complementarity constraints are 
> implemented only on Ipopt-C ( the fortran version of ipopt) .

This is correct.

> I would like to know if you plan to implement them also in the new 
> version ( the C++ version)?

No, there are no plans to include this in the new version of the code. 
But one option is to use a penalty term for the complementarity 
constraints in the objective function, or using other reformulations.

One starting point might be the paper

Baumrucker, B.T., J. G. Renfro and L.T. Biegler "MPEC Problem Formulations 
in Chemical Engineering Applications"

which you can download from here:


> Are bugs still fixed on the fortran version ?

Sorry, no.  The Fortran version is no longer maintained.

Hope this helps,


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