[Couenne] incorrect solution

[Pietro Belotti]

Dear Francois,

the latest stable update of Couenne contains a fix to assign the
correct value to redundant variables such as those in the model you
provided. Let me know if you still get incorrect solutions.

Thanks,
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 04/06/2009, Pietro Belotti <belotti at lehigh.edu> wrote:

> Hi Francois,
>
> I can replicate the problem, which seems to be related x_73 and x_74
> being redundant variables. Each of them is equal to another variable
> (x_58 and x_44 respectively), so Couenne ignores them during
> optimization and sets them to zero. I'll fix this in the next few days.
> The value -13 and 1 of x_58 and x_44 are indeed correct for the bounds
> on x_73 and x_74.
>
> 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 04/06/2009, François Dionne <brainstorm at videotron.ca> wrote:
>
>> Dear mailing list,
>>
>> I downloaded the stable branch of Couenne by SVN on 31 march 2009,
>> compiled it with g++ 4.2.4 and ran it on Ubuntu Linux Hardy Heron.
>> I wrote my model in Ampl and generated some test data.
>>
>> Here's the problem: when I solve the problem, Couenne reports an optimal
>> solution but when I read the value of the variables, one of the integer
>> variables is given a value below its lower bound, in violation of the
>> problem's constraints.
>>
>> You will find a stub named mymodel.nl attached to this message.
>>
>> Goodbye, have a nice day.


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