[Coin-ipopt] How to choose objective functions from multi-objective functions

[Rui Huang]

Hello

I have two objective functions.
So I have two same ampl models, except that each one has a different 
objective function.
and try to solve them together without "reset"
But ampl breaks
"There is more than one objective function in the AMPL model, but 
AmplTNLP::set_active_objective has not been called",

I do not know how to call this function.