[Scip] Howto setup SCIP to solve LP change Matrix and resolve

[fergal mohan]

Hi Timo, that did it, thanks for the pointer to it.
Fergal
P.S. I am using a SCIP_CALL_EXC Macro that I borrowed from Cornelius's queens example which AFAICT does the same thing.

--- On Tue, 7/14/09, Timo Berthold <berthold at zib.de> wrote:

> From: Timo Berthold <berthold at zib.de>
> Subject: Re: [Scip] Howto setup SCIP to solve LP change Matrix and resolve
> To: scip at zib.de
> Date: Tuesday, July 14, 2009, 7:51 AM
> Hi Fergal.
> 
> The method you are looking for is SCIPfreeTransform() (see
> 
> http://scip.zib.de/doc/html/scip_8h.html#9c2399c2334680cd8ad14a1a5ac31622)
> Some explanation on the role of the original and the
> transformed problem is 
> given in Q/A 15 of the SCIP FAQ: http://scip.zib.de/faq.shtml#Q15
> 
> Furthermore, you might consider to use the SCIP_CALL() /
> SCIP_CALL_ABORT() 
> macros for catching the SCIP_RETCODE's. See http://scip.zib.de/faq.shtml#Q17 
> for an explanation and the end of 
> http://scip.zib.de/doc/html/def_8h-source.html for
> their definition.
> 
> I hope that helps resolving your problem.
> 
> Best, Timo
> 
> 
> Am Tuesday 14 July 2009 16:35:25 schrieb fergal mohan:
> > Hi all, I'm getting on well with the implementation of
> the .NET wrapper to
> > use SCIP instead of Soplex but am running into an
> exception when I try to
> > change the Matrix after I've already Solved. If there
> anyting specific that
> > needs to be called after solve before changeing a
> Matrix values. It could
> > be one of the many parameters that I'm passing to
> Create the Constraint or
> > Var but I'm hoping someone can confirm ? I wrote a
> small C++ Test App that
> > I can attach if that helps but the jist of it is the
> below. BTW the
> > getConstraint method calls
> > SCIP_CALL_EXC(SCIPcreateConsLinear(m_pMySCIP, &
> newCons, namebuf,
> > 0, NULL, NULL,
> > MINUSINFINITY, PLUSINFINITY,
> > TRUE, TRUE, TRUE, TRUE, TRUE, FALSE,
> > FALSE, FALSE, FALSE, FALSE));
> > SCIP_CALL_EXC( SCIPaddCons(m_pMySCIP, newCons) );
> > the getValue method calls
> > SCIP_CALL_EXC( SCIPcreateVar(scip, &newvar, name,
> >     0.0, SCIPinfinity(scip), 0.0,
> SCIP_VARTYPE_CONTINUOUS,
> >     TRUE/*initial*/,
> FALSE/*removable*/,
> >     NULL, NULL, NULL, NULL) );
> > Any ideas would be appreciated.
> > Fergal
> > // Test App solves successfully with the following
> call
> > oSCIPPenv->Solve();   
>         // calls SCIPsolve
> > std::cout << "Result is " <<
> oSCIPPenv->GetObjValue() << std::endl;
> > // change a matrix value (2, 0) = 2 and resolve
> > dColValue = 2;
> > if(oSCIPPenv->getConstraint(m_pMySCIP, 2,
> &cons, &wasCreated) == SCIP_OKAY)
> >  if(oSCIPPenv->getVariable(m_pMySCIP, 0,
> &var, &wasCreated) == SCIP_OKAY)
> >   SCIP_CALL_EXC(SCIPaddCoefLinear(m_pMySCIP,
> cons, var, dColValue));
> > oSCIPPenv->Solve();   
>         // calls SCIPsolve
> > <<
> > the call to SCIPaddCoefLinear fails down in the
> SCIPlockVarCons Routine
> > when it appears to be in the wrong (Transformed)
> stage.
> >
> > _______________________________________________
> > Scip mailing list
> > Scip at zib.de
> > http://listserv.zib.de/mailman/listinfo/scip
> 
> 
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