[Osi] Problem using FlopC++ with GLPK

[Ted Ralphs]

It's very possible that you are the first to try that particular
combination, but if things are working with Cbc, I would say that the
problem must either be with Glpk itself or with the implementation of
OsiGlpk. If you want to try to debug it, you should be able to create
the same MIP in LP format and put it directly into OsiGlpk and see
what happens then. aving a test case within Osi will definitely help
us find the problem. Unfortunately, I'm not sure if anyone is actively
developing FlopC++ at the moment, but if the problem is with OsiGlpk,
we should be able to fix it.

Cheers,

Ted

On Sat, Sep 19, 2009 at 12:03 PM, Renato Bruni <bruni at diei.unipg.it> wrote:
> Yes, I tried cbc and it works good.
> Does anybody know if there are incompatibilities between the versions
> of  FlopC++ 1.0.6 and GLPK 4.38? In this case, which version of
> GLPK should be used?
>
> Thanks,
> Renato
>
> ----- Original Message ----- From: "Ted Ralphs" <ted at lehigh.edu>
> To: "Renato Bruni" <renato.bruni at diei.unipg.it>
> Cc: <osi at list.coin-or.org>
> Sent: Saturday, September 19, 2009 4:06 PM
> Subject: Re: [Osi] Problem using FlopC++ with GLPK
>
>
> Did you try it with another solver to see if the result is the same?
> This would tell you whether the problems is with FlopC++ or
> Glpk/OsiGlpk.
>
> Cheers,
>
> Ted
>
> On Thu, Sep 17, 2009 at 12:33 PM, Renato Bruni
> <renato.bruni at diei.unipg.it> wrote:
>>
>> Hello everybody,
>>
>> we have some strange behaviour using FlopC++ 1.0.6 (having inside Osi
>> 0.100.0) and GLPK 4.38.
>>
>> If we run the following example, with 5 variables and 2 constraints, we
>> obtain solution x=(0, 2, 0, 0, 0) and objective= 2
>> but the solution should be x=(4, 0, 0, 0, 0) and objective= 4
>>
>> #include "flopc.hpp"
>> using namespace flopc;
>> #include <OsiGlpkSolverInterface.hpp>
>>
>> int main() {
>> MP_model modello(new OsiGlpkSolverInterface);
>> MP_set N(5);
>> MP_variable x(N);
>> x.integer();
>>
>> MP_constraint vinc1;
>> MP_constraint vinc2;
>> vinc1 = 2*x(0) + 4*x(1) + 6*x(4) == 8;
>> vinc2 = x(0) + x(4) <= 100;
>> modello.add(vinc1);
>> modello.add(vinc2);
>>
>> modello.maximize( x(0) + x(1) + x(4) );
>> x.display("Optimal solution per x:");
>> }
>>
>> If we run this other example, that is the same model with 5 variables and
>> 2 constraints, we obtain solution x=(4, 0, 0, 0, 96) and objective= 4
>> but the solution should be, like before, x=(4, 0, 0, 0, 0) and objective=
>> 4
>>
>> #include "flopc.hpp"
>> using namespace flopc;
>> #include <OsiGlpkSolverInterface.hpp>
>>
>> int main() {
>> MP_model modello(new OsiGlpkSolverInterface);
>> MP_set N(5);
>> MP_set S(5);
>> MP_subset<1> Sub(S);
>> Sub.insert(0);
>> Sub.insert(1);
>> Sub.insert(4);
>>
>> MP_variable x(N);
>> x.integer();
>>
>> MP_data COEFF(Sub);
>> int i;
>> for(i=0; i<Sub.size();i++)
>> COEFF(i)= 2*(i+1);//vector COEFF={2,4,6}
>> COEFF.display("COEFF ");
>>
>> MP_constraint vinc1;
>> MP_constraint vinc2;
>> vinc1 = sum(Sub, COEFF(Sub)*x(Sub))==8;//2x0+4x1+6x4==8
>> vinc2 = x(0) + x(4) <= 100;
>> modello.add(vinc1);
>> modello.add(vinc2);
>>
>> modello.maximize( sum(Sub, x(Sub)) );//max(x(0)+x(1)+x(4))
>> x.display("Optimal solution per x:");
>> }
>>
>> Which can be the reason(s) of this incorrect behaviour?
>> Are there incompatibilities between the versions of FlopC++ 1.0.6 and GLPK
>> 4.38? In this case, which version of GLPK should be used?
>>
>> Thanks for your help.
>> Best regards,
>> Renato Bruni
>>
>>
>> _______________________________________________
>> Osi mailing list
>> Osi at list.coin-or.org
>> http://list.coin-or.org/mailman/listinfo/osi
>>
>
>
>
> --
> Dr. Ted Ralphs
> Associate Professor, Lehigh University
> (610) 628-1280
> ted 'at' lehigh 'dot' edu
> coral.ie.lehigh.edu/~ted
>
>
> _______________________________________________
> Osi mailing list
> Osi at list.coin-or.org
> http://list.coin-or.org/mailman/listinfo/osi
>
>



-- 
Dr. Ted Ralphs
Associate Professor, Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted