[Coin-discuss] Problem in Osi->branchAndBound() (with Clp as linear solver)

[mathieu lacroix]

Hi,

I know that it was not an full tested version and I am really happy you 
have implemented this method. Thanks to it, I have been able to realize 
my project.
I have found a similar solution as :

OsiSolverInterface * newModel = new...;
while ()
{
newModel->loadProblem(...);
  // modify newModel if you want
  newModel->branchAndBound();
  // use results
  delete newModel;
}

I don't really need the correction of this bug as the students' project 
is finished soon (and for my research I use BCP, not OSI with the 
branchAndBound() method).
I just describe the bug to help the development of COIN-OR and prevent 
another people who would want to do the same things as me. If you have 
time to improve and correct this bug it is perfect. If not, that is 
okay. I am sorry to not correct by myself this bug but I am not a good 
developer and I don't know COIN-OR enough to do it (and I don't have 
enough time).

Best regards,

Mathieu LACROIX

John J Forrest wrote:

>Mathieu,
>
>It was only meant to be a simple implementation to help you out not a fully
>tested version.
>
>I will look into it when I get time but why not try  -
>
>OsiClpSolverInterface model - got by some method
>while ()
>  OsiSolverInterface * newModel = model.clone();
>  // modify newModel if you want
>  newModel->branchAndBound();
>  // use results
>  delete newModel;
>}
>
>John Forrest
>
>
>                                                                           
>             mathieu lacroix                                               
>             <mathieu.lacroix@                                             
>             isima.fr>                                                  To 
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>                                                                   Subject 
>             04/07/06 09:18 AM         [Coin-discuss] Problem in           
>                                       Osi->branchAndBound() (with Clp as  
>                                       linear   solver)                    
>             Please respond to                                             
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>
>
>
>Hi,
>
>I use COIN (OSI/CLP) in linear optimization lesson. I need to solve a
>little integer linear problem so I use  the osi method
>branchAndBound().  I thank you a lot to implement the method with the
>linear solver Clp. It work well but  there  still exists a little
>mistake. Indeed, you can't run the branchAndBound method more than once
>on the same OSI object. In this case, it throws an exception. (One
>reason is that when you write the problem in a lp file after running
>once branchAndBound method, the lower and upper bounds of the variables
>are not the initial ones but the one of the optimal solution. But, even
>you change those bounds (setColLower(...) and setColUpper(...)), it
>doesn't work and throws an exception. I think that it is because in a
>more general form, at the end of the branchandbound method, the initial
>data are substituted by other generated and used by the branchAndBound()
>method).
>Or, I have to solve the integer linear problem of 4 variables and one
>constraint several times by changing each time only objective
>coefficients. The only way to do it is to construct each time a new
>problem from scratch or to apply the method loadProblem(...), even if it
>is exactly the same problem you want to solve twice.
>
>Thank you in advance for your answer,
>
>Best regards,
>
>Mathieu LACROIX
>
>
>
>--
>Mathieu LACROIX
>mathieu.lacroix at isima.fr
>Université Blaise Pascal - Clermont Fd II
>Laboratoire LIMOS
>Bâtiment ISIMA - Bureau D112
>Complexe scientifique des Cézeaux
>63 177 Aubière, Cedex - France
>Tel : 04.73.40.79.48
>Fax : 04.73.40.76.39
>
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-- 
Mathieu LACROIX
mathieu.lacroix at isima.fr
Université Blaise Pascal - Clermont Fd II
Laboratoire LIMOS
Bâtiment ISIMA - Bureau D112
Complexe scientifique des Cézeaux
63 177 Aubière, Cedex - France
Tel : 04.73.40.79.48
Fax : 04.73.40.76.39