[Cbc] Fwd: please help

[Haroldo Santos]

On Thu, Oct 4, 2012 at 6:41 AM, Christos <chtsolak at gmail.com> wrote:

>  I am asking you because i have a big problem. With very small alteration
> in data operation time goes from 9' to 65' !!!
>
This is  expected when solving Integer Programs if you are willing to proof
the optimality.
One thing you can do to exit more quickly, if you do not need the optimal
solution (a good one may be enough), is to force the solver to quit after
finding some solutions with the maxSolutions paramater.

>
> Any recommendations on the way i solve the model?
> Do you think that the above times are normal for such a model?
>
>
>
> -------- Original Message --------  Subject: please help  Date: Wed, 03
> Oct 2012 13:13:03 +0300  From: Christos <chtsolak at gmail.com><chtsolak at gmail.com>  To:
> cbc at list.coin-or.org <cbc at list.coin-or.org> <cbc at list.coin-or.org>
>
> Hi all,
>
> i am a student in the final phase of the Milp model which i want to solve.
>
> So, i have a milp model
> columns: 46614
> integers:  12540 (binary)
> rows:        40842
> nonzeros:117823
>
> I tried these simple methods
> 1.
> *solver1.loadProblem(numcols, numrows, start, index, value, collb, colub,
> obj, rowlb, rowub);
> solver1.initialSolve();
> solver1.branchAndBound() ;*
> 2.
> *solver1.loadProblem(numcols, numrows, start, index, value, collb, colub,
> obj, rowlb, rowub);
> CbcModel model(solver1);
> CbcMain0(model);
> const char * argv2[]={"DAS","-solve","-quit"};   *-> *i don't know what
> this do.**
> CbcMain1(3,argv2,model);
>
> *Since i am an amateur, can you help me?
> What method should i use to solve the model? 1,2 or something else?
> Any recommendations?
>
> The 1st takes an hour and stops.
> The 2nd takes either 8' or 35' depending on the data.
>
> Your help is much appreciated.
>
> Christos
>
>
>
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>
>


-- 
=============================================================
Haroldo Gambini Santos
Computing Department - Universidade Federal de Ouro Preto - UFOP
email: haroldo [at ] iceb.ufop.br
home/research page: www.decom.ufop.br/haroldo/

"Computer science is no more about computers than astronomy
is about telescopes." Edsger Dijkstra
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