[Couenne] couenne doesn't exit normally -- Code in Pyomo

[Pietro Belotti]

Hi Nesrine,

it may be a bug in Couenne. To prove it, we need first to prove that
Couenne does receive different inputs when replacing p2/p1 with p2*(p1^-1).
To do so, please find out how to retrieve the .nl files that Pyomo passes
to Couenne or how to save such files from Pyomo with both models; let's
call these f1.nl and f2.nl. Second, run Couenne on f1 and f2 and verify
that the result is different as happened to you in Pyomo. If this happens,
then it's likely the problem is with Couenne, and I'd like to try both .nl
files. Keep in mind that the smaller the model for which the problem can be
replicated, the better, as debugging is easier.

Regards,
Pietro

On Fri, May 4, 2018 at 9:45 PM, Ouanes, Nesrine <
nesrine.ouanes at campus.tu-berlin.de> wrote:

> Hi all,
>
>
> I want to solve my code, which is written in Python and Pyomo, with
> Couenne.
>
> I get an error (Solver (asl) did not exit normally) with no further
> information , whenever I try to solve a code with a division, e.g. I have
> the following constraint:
>
>
> r_p = p2/p1
>
>
> p1, p2 and r_p are variables in my model. I made sure that the bounds for
> p1 don't include the value 0.
>
>
> All other constraints are linear and have no divisions. Couenne works
> fine, when I comment this constraint out. Strangely, Couenne also works
> fine, if I write the constraint as follows:
>
>
> r_p = p * (p1)^(-1)
>
>
> As I'm going to further develop my model and it will eventually have very
> high nonlinearities, I seek your help in understanding, why this problem
> occurs.
>
> Can this be a bug within Couenne? Or perhaps in the Solver interface in P
> yomo?
>
>
> Looking forward to your response.
>
>
> Best,
>
> Nesrine
>
>
>
>
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