[Cbc] Improving performance for binary model

[Haroldo Gambini Santos]

Hi,

It seems that the search is taking too long because CBC cannot find an 
initial integer feasible solution.

...

Cbc0010I After 69 nodes, 41 on tree, 1e+50 best solution, best possible 
232474 (384.80 seconds)

...

Which can always happen since there is no efficient method (with 
theoretical guarantees) even in the best commercial solvers to produce 
an initial feasible solution in polynomial time.

You can try to activate some of the CBC heuristics:

http://www.decom.ufop.br/haroldo/files/cbcCommandLine.pdf

or, even better, devise a problem specific heuristic to feed CBC with an 
initial feasible solution. Even providing a bad (but feasible) initial 
feasible solution (MIPstart) is much better that nothing - cbc has  
improvement heuristics.

Cheers

On 22/11/2019 13:44, Rui Patrocínio wrote:
>
> Hi,
>
>  I'm trying to solve one instance of a problem that is taking a long 
> time to obtain a good solution. Since all variables are binary, 
> probing and implication cuts are doing some work and RINS and Vnd are 
> apparently also improving solutions. For other instances of the 
> problem we are solving, CBC has an acceptable performance but for this 
> instance apparently there's something going wrong (~20 seconds to get 
> the optimum solution with a commercial solver versus never getting the 
> optimum solution with CBC).
>
>  If someone can take a look at the model and give me a hint of what is 
> going on, I would appreciate it.
>
>  The model is at 
> https://drive.google.com/open?id=1bd4jWONmoyAKIi0oLa-AU-ZTu7_8qhb6
>
> -- 
> SISCOG - Sistemas Cognitivos, SA
>
> *Rui Patrocínio*
>
> _______________________________________________
> Cbc mailing list
> Cbc at list.coin-or.org
> https://list.coin-or.org/mailman/listinfo/cbc

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


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the most important.
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