[Coin-discuss] Controlling printing for CbcStrategyDefault

[Kish Shen]

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