[Couenne] Lower/Upper bounds variables

[Luca Mencarelli]

Dear Pietro,

I attach the model and the output files. I get an upper_bound = -210.89,
while the upper bound provided by Couenne (version 0.4.8) is -286.95.
The original problem is a maximization one.

Thanks again. Best,
Luca

-- 
Luca Mencarelli
PhD Candidate at LIX, Ecole Polytechnique
91128 Palaiseau CEDEX, France
Office: 2072 (Bâtiment Alan Turing, second floor)
LIX e-mail address: mencarelli at lix.polytechnique.fr
INRIA e-mail address:  luca.mencarelli at inria.fr



> Hi Luca,
>
> this should not happen, it might be a bug. Can you send me the model
> (a .nl file should suffice)? I suspect the constant term of the
> objective function might be ignored. Also, what version of Couenne are
> you using?
>
> Pietro
>
> On Mon, May 18, 2015 at 4:55 PM, Luca Mencarelli
> <mencarelli at lix.polytechnique.fr> wrote:
>> Dear Pietro,
>>
>> First of thanks very much for the answer. However in the .sol file I
>> found
>> the same values as the one I obtain via the display command. But when I
>> recompute
>> the objective function with these values, it is less than the upper
>> bound
>> provided
>> by Couenne.
>>
>> Best,
>> Luca
>>
>> --
>>
>> Luca Mencarelli
>> PhD Candidate at LIX, Ecole Polytechnique
>> 91128 Palaiseau CEDEX, France
>> Office: 2072 (Bâtiment Alan Turing, second floor)
>> LIX e-mail address: mencarelli at lix.polytechnique.fr
>> INRIA e-mail address:  luca.mencarelli at inria.fr
>>
>>
>>
>>> Hi Luca,
>>>
>>> when Couenne stops before closing the gap, the best feasible MINLP
>>> solution found (if any) is saved in a file with the same name as the
>>> input file but with extension .sol (which is the format read by AMPL).
>>> So the answer is yes for the upper bound if at least one solution is
>>> found.
>>>
>>> However, this does not make much sense for the lower bound, given that
>>> it's obtained by a relaxation of the MINLP (and would hence be
>>> infeasible) and is related to the whole branch-and-bound search tree
>>> rather than a specific subproblem. Hence no solution is available for
>>> the lower bound.
>>>
>>> Hope this helps,
>>> Pietro
>>>
>>>
>>> On Mon, May 18, 2015 at 11:05 AM, Luca Mencarelli
>>> <mencarelli at lix.polytechnique.fr> wrote:
>>>> Hi,
>>>>
>>>> If Couenne did not succeed in solving a problem to optimality, it's
>>>> possible to
>>>> retrieve the values of the decision variables corresponding to the
>>>> lower
>>>> and to
>>>> the upper bounds provided by the solver?
>>>>
>>>> Thanks. Best,
>>>> Luca
>>>>
>>>> --
>>>> Luca Mencarelli
>>>> PhD Candidate at LIX, Ecole Polytechnique
>>>> 91128 Palaiseau CEDEX, France
>>>> Office: 2072 (Bâtiment Alan Turing, second floor)
>>>> E-mail address: mencarelli at lix.polytechnique.fr
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Couenne mailing list
>>>> Couenne at list.coin-or.org
>>>> http://list.coin-or.org/mailman/listinfo/couenne
>>>
>>
>>
>
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