[Couenne] generate .nl file from AMPL

[Pietro Belotti]

Hello David,

> 1) What's the exact syntax to generate a .nl file from my myampl.mod ? I
> tried unsuccessfully "write gmyampl", "write gmyampl.nl"

"write gmyampl;" always works for me. Did you put the ";" at the end  
of the command?

> 2) Does a maximization objective in the original file need to be transformed
> in a minimization one , or can Couenne read it directly in the nl file ?

Couenne reads maximization problems. However, for a maximization  
problem max {f(x):x in X} Couenne reports the global minimum of the  
transformed problem, i.e., min {-f(x): x in X}, without restoring the  
sign. AMPL, instead, does return the value with the right sign, -min  
{-f(x): x in X}.

Hope this helps.

Best,
Pietro

_________________________________________
Pietro Belotti, Lehigh University
Dept. of Industrial & Systems Engineering
200 W Packer Ave, Bethlehem PA 18015.
phone: 610-758-3865   fax: 610-758-4886
email: belotti at lehigh.edu
web:   http://www.lehigh.edu/~pib208


On 10/05/2009, David Gravot <dgravot at noos.fr> wrote:

> Hello,
>
> I'm trying to test Couenne on a non-linear non-convex problem that comes
> from an AMPL modeling, say  myampl.mod . Two naïve questions :
>
> 1) What's the exact syntax to generate a .nl file from my myampl.mod ? I
> tried unsuccessfully "write gmyampl", "write gmyampl.nl"
> 2) Does a maximization objective in the original file need to be transformed
> in a minimization one , or can Couenne read it directly in the nl file ?
>
> Thanks
>
> David Gravot
> dgravot at noos.fr
>
> ROSTUDEL Operations Research
> www.rostudel.com
>
>
>
> _______________________________________________
> Couenne mailing list
> Couenne at list.coin-or.org
> http://list.coin-or.org/mailman/listinfo/couenne


----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.