[Cbc] Getting information from running model in CbcMain1

[Stefan Vigerske]

Hi,

I do this by given a callback function to CbcMain1.
The callback always gets the current model, so you can get, e.g., the
model after preprocessing.

It looks like the following:

CbcModel* preprocessedmodel=NULL; /* global variable */
int gamsCallBack(CbcModel* currentSolver, int whereFrom) {
     if (whereFrom==3) preprocessedmodel=currentSolver;
     return 0;
}

int main (int argc, const char *argv[]) {
 ...
 CbcModel model(lp);
 ...
 CbcMain1(par_list_length,cbc_args,model,gamsCallBack);
 ...
}

See
https://projects.coin-or.org/GAMSlinks/browser/stable/0.4/GAMSlinks/src/Cbc/GamsCoinCbc.cpp
for the full code.

Best,
Stefan

acw at ascent.com wrote:
> We have a Cbc application modeled on Cbc/examples/driver4.cpp; in 
> particular, it uses the function CbcMain1 to actually launch the solution.
> 
> In a previous version of the same application, we mimicked something much 
> simpler, more like driver1.cpp.  In that version, we were able to monitor 
> the problem as it was being solved.  We used calls like 
> CbcModel->getObjValue() in another thread to watch the objective 
> improving.  (We are aware of thread hazards, but we were pretty careful to 
> protect ourselves from them.)
> 
> When we switched to the driver4-like approach, this stopped working. 
> CbcMain1 makes its own copy of the given Cbc model, and it is on this copy 
> (called "cbcModel" in the code, which is in CbcSolver.cpp) that 
> CbcModel.branchAndBound() is actually invoked.  Poking the original model 
> to find out its best objective so far, or the number of nodes it has 
> processed, doesn't work.
> 
> Is there a right way to expose this copied model so that outside code can 
> query its progress?  I'm reluctant to mess around with the code in 
> CbcSolver.cpp, but will do that if I have to.
> 
> 
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-- 
Stefan Vigerske
Humboldt University Berlin, Numerical Mathematics
http://www.math.hu-berlin.de/~stefan