[Scip] Elements of a subset

[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
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>> 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
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