[Scip] Getting duals values of best solution

[Thomas Schlechte]

Dear Abdelkader,

have a look at

http://scip.zib.de/doc/examples/Binpacking/

and in particular

http://scip.zib.de/doc/examples/Binpacking/pricer__binpacking_8c_source.shtml

Good luck.
Thomas


> Hi Rodolfo,
> Thank's for reply.
> But when applying pricing, we use dual values to get the reduced cost,in
> my case, i don't get the correct values of dual variables.The earlier
> example is one iteration of column generation, at these stepscip found the
> optimal solution of the master problem, so no need to generate new
> columns,the problem is that the value of dual variable are all zero, which
> is not correct, and scipcontinue to generate new columns.
> So how we can get dual variables in pricing if scip don't provide dual
> information ?
> Best regards
> A. Ouali
>
>
> Date: Thu, 16 Oct 2014 18:17:20 -0300
> Subject: Re: [Scip] Getting duals values of best solution
> From: rodolfo.carvajal at gmail.com
> To: oualiaek at hotmail.fr
>
> Hi Abdelkader,
>
> If you solve your MIP as a SCIP problem, you don't get dual information
> (see the SCIP FAQ http://scip.zib.de/#faq).
>
> You can use the LP interface (lpi/lpi.h) to interact with the LP solver
> and get the duals.
> Hope this helps,
>
> Rodolfo
> On Oct 16, 2014 5:49 PM, "Abdelkader Ouali" <oualiaek at hotmail.fr> wrote:
>
>
>
> Dear scip users,
> I have a short example of ILP, and i want to know how to get dual values
> of optimal solution,when i use cplex, it give me the correct value of dual
> variables,but when using scip the dual values is all zero, knowing that i
> set the pointers of constraint to the transformedones, in attachment you
> will find source code containing the example and how i do to get the dual
> values.
> I want to know what is wrong in this code ?
> Best regards
> A. Ouali
>
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_____________________________________________

Dr. Thomas Schlechte
Zuse Institute Berlin
Takustrasse 7, D-14195 Berlin-Dahlem, Germany
phone: +49-30 841 85 317
fax: +49-30 841 85 269
url: http://www.zib.de/schlechte
e-mail: schlechte at zib.de
_____________________________________________