[Cbc] Fwd: please help

[Haroldo Santos]

Some options may accelerate (or slowdown) a lot. Heuristics usually have a
huge impact on the solution time. Try including

cbc air04.mps.gz passF 100 solve

Also, if you to not need the optimality proof you can disable cuts

cbc air04.mps.gz passF 100 cuts off solve

[]'s

On Fri, Oct 5, 2012 at 5:20 AM, Christos <chtsolak at gmail.com> wrote:

>  Thank you for your suggestion, i will check it and let you know.
>
> But i think the problem is elsewhere.
> When i solve the same problem with gams via cbc solver it takes 30-60
> seconds, and not 60 minutes!
> Why?
>
>
> On 4/10/2012 17:57, Haroldo Santos wrote:
>
> 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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>> http://list.coin-or.org/mailman/listinfo/cbc
>>
>>
>
>
> --
> =============================================================
> 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
>
>
>
>


-- 
=============================================================
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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