[Cbc] Using SOS with CbcModel/CbcSolver

[Kish Shen]

Hi,

I am looking at the issue of adding SOS to a problem to be solved by 
CBC. I last looked at this about 3 years ago, and wrote some code to add 
a CbcSOS object via addObjects() to a CbcModel. However, this code is 
commented out, with the comment that SOS cannot be added to a 
preprocessed problem.

As I said, this was done 3 years ago, when I first wrote the code for 
our interface to CBC. My code have changed significantly since then, in 
particular it now uses CbcSolver rather than CbcModel directly. I assume 
there may be changes in CBC since that time too, so I am wondering if I 
can now add SOS to the problem.

Currently, the problem is stored in a OsiClpSolverInterface, which is 
cast to a CbcModel:

CbcModel* model = new 
CbcModel(static_cast<OsiSolverInterface&>(*clpmodel);

and the problem is then solved using CbcMain0 and CbcMain1:

CbcMain0(*model);
...
CbcMain1(5, cbc_args,*model.callBack);

Can I add SOS during this process, and if there are still any conditions 
to when I can add the SOS?

Thanks in advance for any information!

Cheers,

Kish

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