[Scip] Elements of a subset

Tue Sep 27 16:10:56 MEST 2011

I'm sorry to bother you guys. Best of lucks.
-------------------------------------------------
Julio Rojas
jcredberry at gmail.com


On Tue, Sep 27, 2011 at 4:09 PM, Ambros Gleixner <gleixner at zib.de> wrote:
> Dear Julio,
>
>
>
> Dear Julio.
>
> This mailing list mainly focuses on questions about the usage of SCIP.
> When it is about your model, then you are the expert and you will be
> best suited to analyze it. For your infeasibility, e.g., try to solve
> the model with an LP solver - if this is already infeasible, look at the
> farkas proof. Or introduce slacks into your model and try to minimize
> their sum or maximum. Et cetera. There might be mailing lists focussing
> on general modelling questions which you might want to address.
>
> When you have a specific question on how to achieve something with SCIP,
> Zimpl, or SoPlex, come back and ask us - we are happy to help!
>
> Best regards,
> ambros
>
>
> Am 27.09.2011 15:22, schrieb Julio Rojas:
>> Dear Ambros,
>>
>> Yes I have seen and tried the vif keyword. Nonetheless, as you can see in my
>> previous email, I have made an example without the need to use "vif"
>> clauses. The problem is that the constraints seem to be making the problem
>> an unfeasible one. I hope somebody could take a look to the code and point
>> to me the problems.
>>
>> Again, thanks for your help.
>> -------------------------------------------------
>> Julio Rojas
>> jcredberry at gmail.com
>>
>>
>> On Tue, Sep 27, 2011 at 2:52 PM, Ambros Gleixner <gleixner at zib.de> wrote:
>>
>>> Dear Julio.
>>>
>>> The "with" construct needs a boolean expression which is known at
>>> "compile" time, i.e., may not contain variables.
>>>
>>> Have you seen the "vif" keyword which can be used to automatically
>>> generate Big-M formulations, Zimpl manual 4.12?
>>>
>>> ambros
>>>
>>>
>>> Am 27.09.2011 09:53, schrieb Julio Rojas:
>>>> Thx Ambros. One question, would this give me all<f,c>  for which
>>>> P[f,c]==1? P[f,c] is a decision variable, so the number of constraints
>>>> will be constantly changing. I guess this is not possible, is it?
>>>>
>>>> Regards.
>>>> -------------------------------------------------
>>>> Julio Rojas
>>>> jcredberry at gmail.com
>>>>
>>>>
>>>>
>>>> On Mon, Sep 26, 2011 at 8:56 PM, Ambros Gleixner<gleixner at zib.de>
>>>  wrote:
>>>>> Dear Julio.
>>>>>
>>>>> First, you need to use the "with" keyword as described in Section 4.7 of
>>>>> the Zimpl manual. Something like
>>>>>
>>>>>    forall<f,c>  in FC with P[f,c]==1 do
>>>>>       ax[f]>= max(xf[f]) - min_j(xf[f]);
>>>>>
>>>>>
>>>>> should do.
>>>>>
>>>>> Second, examples on how to get maximum and minimum values can be found
>>>>> on page 10 of the Zimpl manual.
>>>>>
>>>>> Hope that helps,
>>>>> ambros
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Am 26.09.2011 17:53, schrieb Julio Rojas:
>>>>>> Dear all. Stefan Vigerske helped me with the reformulation of a
>>>>>> constraint I had, but latter on I saw that I originally exposed it
>>>>>> badly. I had:
>>>>>>
>>>>>>     ax[f]>= max(xf[f]*P[f,c]) - min(xf[f]*P[f.c])
>>>>>>
>>>>>> when I reality I need:
>>>>>>
>>>>>> forall<c>  in C and forall P[f,c]==1:  ax[f]>= max(xf[f]) -
>>> min_j(xf[f])
>>>>>>
>>>>>> How can I write these constraints in ZIMPL? Until now, I have this:
>>>>>>
>>>>>> set F :={1..4};
>>>>>> set C :={1..2};
>>>>>> set FC := F*C;
>>>>>> param xf[F]:=<1>  1.5,<2>  4,<3>  4.5,<4>  1.5;
>>>>>> param yf[F]:=<1>  4,<2>  4,<3>  1.5,<4>  2;
>>>>>> param xc[C]:=<1>  3,<2>  3;
>>>>>> param yc[C]:=<1>  4,<c>  2;
>>>>>> param d[FC] :=
>>>>>>    |    1,    2|
>>>>>> |1| 1.50, 2.50|
>>>>>> |2| 1.00, 2.24|
>>>>>> |3| 2.92, 1.58|
>>>>>> |4| 2.50, 1.50|;
>>>>>> var X[C] binary;
>>>>>> var P[FC] binary;
>>>>>> minimize bs: sum<c>  in C: X[c];
>>>>>> subto maxdist:
>>>>>>    forall<f,c>  in FC do d[f,c]*P[f,c]<= 2;
>>>>>> subto onlyone:
>>>>>>    forall<f>  in F do sum<c>  in C: P[f,c]==1;
>>>>>>
>>>>>> Thanks.
>>>>>>
>>>>>> -------------------------------------------------
>>>>>> Julio Rojas
>>>>>> jcredberry at gmail.com
>>>>>> _______________________________________________
>>>>>> Scip mailing list
>>>>>> Scip at zib.de
>>>>>> http://listserv.zib.de/mailman/listinfo/scip
>>>>>
>>>>> --
>>>>> ____________________________________________________________
>>>>> Ambros M. Gleixner
>>>>> Zuse Institute Berlin - Matheon - Berlin Mathematical School
>>>>> http://www.zib.de/gleixner
>>>>> _______________________________________________
>>>>> Scip mailing list
>>>>> Scip at zib.de
>>>>> http://listserv.zib.de/mailman/listinfo/scip
>>>>>
>>> _______________________________________________
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>>
>
> --
> ____________________________________________________________
> Ambros M. Gleixner
> Zuse Institute Berlin - Matheon - Berlin Mathematical School
> http://www.zib.de/gleixner
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