[Scip] Getting duals values of best solution

[Abdelkader Ouali]

Hi Diego,
So, the problem is in my implementation, if it works for you, it must works for me...perhaps i have missed something, i will check again upon the example given by Thomas,
Anyway thanks for help
A. Ouali  

Date: Fri, 17 Oct 2014 08:28:03 +0200
From: dponce at us.es
To: oualiaek at hotmail.fr
CC: rodolfo.carvajal at gmail.com; scip at zib.de
Subject: Re: [Scip] Getting duals values of best solution



Hi Abdelkader,

you wrote that you have used the transformed ones, but for me it works in my pricing by means of functions SCIPgetTransformedCons() and SCIPgetDualsolLinear(). They are used in VRP example.

Sorry if this is not new information for you.

Diego.

 

 
El 17/10/2014 01:26, Abdelkader Ouali escribió:


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 step
scip 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 scip
continue 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 transformed
ones, 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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