[Ipopt] round(x,n) in objective function

[Hans Pirnay]

On Wed, Jun 6, 2012 at 1:19 PM, Novalio Daratha <novatha at gmail.com> wrote:
> Dear All,
>
> I am a new user of AMPL and IPOPT. When my objective function contains
>
>       round(x,n),
>
> ipopt crashes with:
>
>       exit code 3221225477
>
> Does this mean Ipopt can not handle this in objective function?

For Ipopt to work, you need differentiability for all constraints and
the objective. The round function is not differentiable, so this is
not going to work.

> Is there an alternative way of getting the same result?

Can you tell us what you are trying to model with the round function?

best
Hans