[Couenne] Objective fn value

[Akshay Gupte]

Pietro,
I think I may have found another possible cause of this bug. After 
playing around with Couenne options in <couenne.opt> file, I noticed 
that whenever I removed
lp_solver cplex

the values displayed within AMPL were correct.

Regards,
Akshay Gupte
Ph.D. student
Operations Research
Georgia Tech


On 8/30/2011 12:35 AM, Pietro Belotti wrote:
> Thanks. Unfortunately I cannot reproduce the problem: if I run the 
> .run file attached, I get the output in the .txt attachment, and both 
> display instructions show an objective function of -877, which seems 
> correct. What command do you use to display the objective's value?
>
> Regards,
> Pietro
>
> -- 
> Pietro Belotti
> Dept. of Mathematical Sciences
> Clemson University
> email: pbelott at clemson.edu
> phone: 864-656-6765
> web:   myweb.clemson.edu/~pbelott
>
> On Mon, 29 Aug 2011, Akshay Gupte wrote:
>
>> Pietro,
>> I am attaching a sample model and data file. When I try to display 
>> the objective value via AMPL, I get a return value of zero.
>>
>> Regards,
>> Akshay Gupte
>> Ph.D. student
>> Operations Research
>> Georgia Tech
>>
>>
>> On 8/25/2011 9:58 PM, Pietro Belotti wrote:
>>> Akshay,
>>>
>>> it seems this might be related to a constant value of the objective 
>>> function, i.e., after some AMPL preprocessing the problem is of the 
>>> form min {c: x in X}, with c a constant.
>>>
>>> I'll submit a ticket. I was able to create a problem that replicates 
>>> the behavior you describe, but can you attach a model where this 
>>> happens?
>>>
>>> Thanks,
>>> Pietro
>>>
>>> -- 
>>> Pietro Belotti
>>> Dept. of Mathematical Sciences
>>> Clemson University
>>> email: pbelott at clemson.edu
>>> phone: 864-656-6765
>>> web:   myweb.clemson.edu/~pbelott
>>>
>>> On Wed, 24 Aug 2011, Akshay Gupte wrote:
>>>
>>>> Hi
>>>> I am using the stable 0.4 version. I noticed that after Couenne 
>>>> finished it's solve, the optimal (or best found) value displayed by 
>>>> Couenne is completely different from the value using the foll. 
>>>> command in Ampl
>>>>
>>>> display obj.val;
>>>>
>>>> This happened for many instances that I was trying. In some cases, 
>>>> the value displayed from within Ampl was simply zero. Is it 
>>>> possible that the link with Ampl is broken somewhere ?
>>>>
>>>> Akshay Gupte
>>>>
>>>> Sent from my iPhone
>>>>
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>>