[Coin-discuss] CBC Pre/postprocessing

[John Forrest]

I have modified CbcModel.cpp in trunk and 2.6.  Fixes problem on my one
simple test.

John Forrest

On Wed, 2011-05-25 at 14:49 +1200, Geoff Leyland wrote:
> Hi,
> 
> As far as I can tell, if I set up preprocessing on a CBC model with:
> 
>   CbcStrategyDefault *s = new CbcStrategyDefault(true, 5, 0, 2);
>   s->setupPreProcessing();
>   model->setStrategy(s);
> 
> Then when I 
> 
>   model->initialSolve();
>   model->branchAndBound();
> 
> the model will be preprocessed before the solve starts, and postprocessed once the solve ends.  However (again, as far as I can tell), if the problem has no integers, then it is not postprocessed.  I think the offending code starts at CbcModel line 2009:
> 
>     } else if (!numberObjects_) {
>         // nothing to do
>         solverCharacteristics_ = NULL;
>         bestObjective_ = solver_->getObjValue() * solver_->getObjSense();
>         int numberColumns = solver_->getNumCols();
>         delete [] bestSolution_;
>         bestSolution_ = new double[numberColumns];
>         CoinCopyN(solver_->getColSolution(), numberColumns, bestSolution_);
>         return ;
>     }
> 
> In contrast to the other early returns, there's still a valid solution when there's no integers, so I think so postprocessing should happen here.
> 
> Cheers,
> Geoff
> 
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