[Coin-ipopt] How to guilde the search in IPOPT

[Dahai Xu]

Hi,

I am using IPOPT-C (2.2.1e) with AMPL to solve a network optimization 
problem. Its performance is very impressive for some topologies. I am trying 
to improve its robustness on various topologies by tuning some parameters of 
IPOPT. My questions are:

1) Do you have any timeframe to support complementarity formulations in 
IPOPT version 3.0 and above?

2) If I know the bound of the objective function, how can I specify it as a 
cut in AMPL for IPOPT? Can the objective cut help IPOPT avoid some 
unnecessary tries (.i.e. speed up the search process)?

3) How can I specify "control" variables in AMPL for IPOPT given that I 
don't know how AMPL names these "control" variables?

4) I try to add some additional (redundant) constraint cuts to speed up the 
search. Sometimes, these cuts indeed speed up the process but sometimes they 
lead to a much worse solution than before. How can I differentiate the 
importance of equations in measuring the constraint violation?

Thanks a lot for the excellent software and have a good weekend!

Yours sincerely
Dahai Xu