[Ipopt] Slack variables too small

[Fabio Ronchini]

Hello everyone,

I am having a hard time with Ipopt to minimize the curve length of a curve
family. In the optimization problem I have no constraints, and all six
variables are chosen in a compact interval.

During the optimization process, Ipopt prints "6 slacks too small,
adjusting variable bounds", then performs a new iteration. It all repeats
for the last four iterations and then exits with "EXIT: Optimal solution
found", giving me a solution which is clearly NOT the shortest curve. Also
the gradient vector shows clearly that this is not a local minimum.

I fear this variable bounds adjustments may interfere with the optimization
process, but I have found nothing in the documentation about what this is
or how can one control it. Can someone help, please?

Thanks,

Fabio Ronchini

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