[Cgl] cgl, cpx, mir, error

[Matthew Galati]

As a temp fix, can't you just have a base implementation of getRowActivity( ) = Ax* in the base Osi class? Then, in things like OsiCpx, where it will otherwise fail - check for errors, if it fails, use the base implementation? It's slow, since you have to calculate Ax* each time you call that. But, its better than not working at all.

Matt



-----Original Message-----
From: Ted Ralphs [mailto:tkralphs at Lehigh.EDU] 
Sent: Wednesday, April 11, 2007 5:45 PM
To: cgl at list.coin-or.org
Cc: Matthew Galati
Subject: Re: [Cgl] cgl, cpx, mir, error

One workaround is not to use OsiCpx :). I guess it wouldn't be that difficult to patch OsiCpx it so that it uses cached info. Or patch
CglMixedIntegerRounding2 so that it doesn't make that call. But someone has to take the time to do it. If someone does, I'll try to get the matches in.

Cheers,

Ted

Ted Ralphs wrote:
> There is a call to getRowActivity() in CglMixedIntegerRounding2. In 
> OsiCpx, this call is implemented through a call to CPLEX, which 
> complains that there is no solution whenever you have not just 
> finished solving the loaded instance (which it looks like you have 
> not. The other cut generators seem only to use calls that require 
> returning information cached in the interface layer, so you don't get the error.
> 
> Cheers,
> 
> Ted
> 
> Matthew Galati wrote:
>> Hi.
>>
>> I am creating an OsiCpx object, populating a model, setting the primal solution, and then calling the MIR cut generator.
>>
>> OsiSolverInterface * siCgl = new OsiLpSolverInterface();
>>
>>   siCgl->loadProblem(*m_modelCore->M,
>>                        &m_modelCore->colLB[0],
>>                        &m_modelCore->colUB[0],
>>                        m_app->m_model.objCoeff, 
>>                        &m_modelCore->rowLB[0],
>>                        &m_modelCore->rowUB[0]);
>>
>>    siCgl->setInteger(&m_modelRelax->integerVars[0],
>>                       static_cast<int>(m_modelRelax->integerVars.size()));
>>    siCgl->setColSolution(m_xhat);
>>
>>    CglMixedIntegerRounding2 cglMirs;
>>    cglMirs.generateCuts(*siCgl, cs);
>>
>> And, I get the error from Cplex:
>>   CPLEX Error  1217: No solution exists.
>>
>> Note: I don't get that error with Cliques/Knap/Flow CGLs.
>>
>> Any ideas?
>>
>> Thanks,
>> Matt
>>
>> _______________________________________________
>> Cgl mailing list
>> Cgl at list.coin-or.org
>> http://list.coin-or.org/mailman/listinfo/cgl
> 
> 


--
Dr. Ted Ralphs
Associate Professor
Industrial and Systems Engineering
Lehigh University
(610)758-4784
tkralphs at lehigh.edu
www.lehigh.edu/~tkr2