[Scip] why might this short 3 constraint program be infeasible?

[George Nychis]

Thanks Michael and Gerald!

This was a huge help to me, thanks for the explanations.  I figured it
would be a simple issue. I'm just trying to learn all of these intricacies
of mixed integer programming, zimpl, etc.

- George


On Mon, Sep 16, 2013 at 5:31 PM, Gerald Gamrath <gamrath at zib.de> wrote:

>  Hi George,
>
> the reason is simple: 'a' needs to take on the value of -14.666667 in
> order to make the constraint "aval" feasible. However, if you do not
> specify a lower bound for a variable, ZIMPL assumes the variable to be
> nonnegative (which is consistent to the lp file format, by the way).
>
> In order to get a free variable, you need to specify a lower bound of -
> infinity, i.e.,
> var a >= -infinity;
>
> If you do this, everything works fine.
>
> Best,
> Gerald
>
>
>
>
> Am 16.09.2013 21:58, schrieb George Nychis:
>
> Hi all,
>
>  I'm trying to figure out why the solution to this short attached ZMPL
> example is infeasible.  I believe that 'a' taking on the value of 14.666667
> provides an answer, but I don't know hot SCIP is meant to handle that
> repeating digit.
>
>  - George
>
>
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