[Cbc] Problem writing SOS2 constraint in the Lp file

[Alexis Guigue]

Hi,

I am not able to write the SOS2 constraint in the Lp file. Here is what 
I am doing:

// Create an OsiClpSolverInterface object
OsiClpSolverInterface    m_osiClpSolver;

// Populate the solver
m_osiClpSolver.loadProblem(matrix, &m_vColLower[0], &m_vColUpper[0], 
&m_vObjCoef[0], &m_vSign[0], &m_vRHS[0], 0);

// Set continuous variables
m_osiClpSolver.setContinuous(&m_vContVarIndex[0], 
(int)m_vContVarIndex.size());

// Set column and row names
m_osiClpSolver.setIntParam(OsiNameDiscipline,2);
for(int i=0;i<(int)m_vRowName.size();i++) 
m_osiClpSolver.setRowName(i,m_vRowName[i]);
for(int i=0;i<(int)m_vColName.size();i++) 
m_osiClpSolver.setColName(i,m_vColName[i]);

(**)

// Create the CbcModel object
CbcModel cbcModel(m_osiClpSolver);

// Add sos2 constraint to CbcModel
  cbcModel.addObjects(...,...);

(***)

// Optimize
cbcModel.branchAndBound();

Now, I am curious to have a look at the lp file.
If I insert

m_osiClpSolver.writeLp(FILENAME);

where (**) is, then I get the lp file without the SOS2 constraint (which 
makes sense to me).

I have tried to insert

cbcModel.solver()->writeLp(FILENAME); or 
cbcModel.referenceSolver()->writeLp(FILENAME);

where (***) is. I still get the same lp file, without the SOS2 constraint.

Am I doing something wrong? How can I get my lp file with the SOS2 
constraints included?

Thanks in advance.

Cheers

Alexis

-- 
Software Engineer/Research Engineer
Softree Technical Systems Inc.
www.softree.com
Engineering an Easier Way