[Coin-ipopt] User option not being set

[Andreas Waechter]

Hi Rodrigo,

> I'm not sure what this means but when I set required_infeasibility_reduction
> to 0.1 in ampl either by ipopt.opt file or with ipopt_options I keep
> getting:
>
>                                    Name   Value                used
>                      print_user_options = yes                   yes
>        required_infeasibility_reduction = 0.1                    no
>
> How come the option is not being used? Or does this message mean something
> else??

The meaning of required_infeasibility_reduction is as follows:

Say, the restoration phase is activated at an iterate x_k.  Then the 
restoration phase will continue until it finds a point that is acceptable 
to the filter as it was in this iteration (augmented by the point x_k) AND 
when the infeasibility at the new point is less than 
required_infeasibility_reduction times the infeasibility at x_k.  With 
your setting, you essentially tell Ipopt that is had to continue with the 
restoration phase until the infeasibility is reduced by at least 90% 
compared to where it is started.

As for the output you looked at above:  Even though it might seem like 
that, the option required_infeasibility_reduction IS used.  The reason you 
don't see that in the output has to do with the particular way the options 
are processed for the restoration phase (which is a recursive invokation 
of Ipopt).

I hope this helps,

Andreas