[Scip] help : How to write dual problem

[Abdelkader Ouali]

Dear Gregor,
Yes, i confirm very nice as an exercice ;)It's much clear, now
Thank's and regards 
---Abdelkader Ouali   
Date: Wed, 9 Jul 2014 17:19:06 +0200
From: hendel at zib.de
To: scip at zib.de
Subject: Re: [Scip] help : How to write dual problem


  
    
  
  
    Dear Abdelkader Ouali,

      

      I am afraid there is no ad-hoc method available for this in SCIP.
      The methods available through the linear
        constraint

        handler might be sufficient here:

      

      1. Create a secondary SCIP-instance dualscip and a problem inside
      dualscip.

      2. Create variables for every linear constraint in dualscip

      3. Create a new linear constraint in dualscip for every variable

      4. Iterate over the constraints once in order to have their
      variables, vals (=coefficients), and number, and add

      the coefficients for the corresponding dual variable of this
      constraint to every dual constraint it should appear in.

      5. Now you can use the LP-writer for the dualscip-Problem.

      

      This is quite a nice SCIP-exercise, isn't it? :)

      

      The reason why SCIP does not come with such a functionality (yet)
      is its constraint-based nature. It does not

      always make sense to speak of the dual of a SCIP problem. The dual
      of the LP that SCIP builds internally might

      be different from what you exspect, because the problem has
      already undergone a transformation through

      various presolving steps.

      

      Kind regards

      Gregor

      

      

      Am 09.07.2014 10:01, schrieb Abdelkader Ouali:

    
    
      
      Hello,
        

        
        How to write dual problem of the original problem in lp
          format file 
        using SCIP routines
        

        
        Thanks 
        

        
        ---
        Abdelkader Ouali
        

        
      
      

      
      

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