[Coin-discuss] Controlling printing for CbcStrategyDefault

[Kish Shen]

John,

Thanks for looking at this. 

For my tests, the problems that are solved are specified in our Constraint 
Logic Programming language ECLiPSe, and that problem is then trasnsferred to 
OsiClpSolver via my interface code, so the problem is not read from an MPS 
file. I expect that the rows/columns ordering of the problem to be different 
from what you might get from an MPS file, and there are probably other 
differences. 

I am trying to generate the calls we made to  Osi/Clp/Cbc, which will allow 
you to compile a program independent of ECLiPSe, which will hopefully 
reproduce the problem.

Thanks and Cheers,  

Kish

On Sunday 09 July 2006 21:48, John J Forrest wrote:
> Kish,
>
> I can not reproduce error messages.
>
>
>
>
>
>              Kish Shen
>              <kish.shen at crossc
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>                                                                    Subject
>              07/09/06 02:17 AM         Re: [Coin-discuss] Controlling
>                                        printing for CbcStrategyDefault
>
>              Please respond to
>              Discussions about
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>
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>
>
>
> Hi,
>
> On Saturday 08 July 2006 07:31, Kish Shen wrote:
> > One question about this preprocessing: do you expect it to improve the
> > performance? In my case, I have already called CglPreprocess on the
>
> problem
>
> > when it was first copied from the OsiClpSolver to the CbcModel, and in
>
> the
>
> > rather limited test examples I have been running (mainly used to test if
>
> my
>
> > changes are working, rather than for measuring performances), where some
> > MIPLIB problems are solved (but they are modelled in our ECLiPSe
> > programming language, rather than read in from an MPS file), doing this
> > second preprocessing in CbcStrategy does not improve the solving times,
>
> and
>
> > in fact for one problem (noswot), it slows the solving time time from 33s
> > to 54s.
>
> I decided to try out some more tests with my code. With the
> CbcStrategyDefault
> set for the CbcModel  (model is a CbcModel*):
>
>    (code taken and modified from sample2.cpp in Cbc Samples directory)
>     // Set up pre-processing to find sos if wanted
>     if (lpd->presolve) strategy.setupPreProcessing(2);
>     //strategy.setupPrinting(*model, 0);
>     model->setStrategy(strategy);
>     model->branchAndBound();
>
> this generally solved the problems faster than if the strategy
> preprocessing
> and setStrategy code is commented out. However, for a couple of the
> problems
> I tried (versions of MIPLIB's cap6000 and aflow30a), I got what looks like
> error messages from Clp:
>
> Clp6002E 1 bad bound pairs or bad objectives were found - first at C3013
> Clp6002E 1 bad bound pairs or bad objectives were found - first at C1987
> Clp6002E 1 bad bound pairs or bad objectives were found - first at C3863
>
> the actual objective value for the MIP problem after the search appears to
> be
> correct though. Is the above a potential problem, or are such messages
> expected?
>
> aflow30a, in addition to generating Clp error messages like the above, also
>
> ran much slower with the CbcStrategyDefault than without -- slowing down
> from
> 2000 seconds to 6500 seconds, the only problem to do so. Is this related to
>
> the above messages?
>
> Cheers,
>
> Kish Shen
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