[Cbc] Segfault / memory corruption after "assignSolver" in "CbcModel"

[Dirk Eßer]

Hello,

I have a little problem adding a preprocessing step to program doing MIP 
solving using the CBC library. The problem is, that the program fails 
with more or less random memory corruption (and in the better cases: 
with a segfault) some of the time.

The CbcModel instance is created programmatically

    OsiClpSolverInterface iface;
    CoinPackedMatrix pmx(false, num_columns, num_rows, num_elements,
    matrix, columns, starts, lengths);

    iface.setObjSense(-1.0);
    iface.loadProblem(pmx, 0, 0, objective, senses, rights, 0);
    iface.passInMessageHandler(&printer);

    model_ptr LP(new CbcModel(iface));
    ... adding stuff via LP->addObjects(...) to declare integer
    constraints on variables and a few SOSes ...

Things work fine, if we directly compute a solution without further 
preprocessing via

    LP->initialSolve();
    LP->branchAndBound();

We now try to add a pre-processing step to the solution process. As a 
starting point, we used the driver code generated by the CBC command 
line tool ("-cpp 0", which doesn't compile).

    OsiSolverInterface* original_solver = LP->solver();
    OsiSolverInterface* cloned_solver = original_solver->clone();
    OsiSolverInterface* configured_solver = 0;

    cloned_solver->passInMessageHandler(LP->messageHandler());
    cloned_solver->setHintParam(OsiDoInBranchAndCut, true, OsiHintDo);

    CglPreProcess processor;

                 {
                     CglProbing prober;
                     prober.setUsingObjective(1);
                     prober.setMaxPass(3);
    prober.setMaxProbeRoot(cloned_solver->getNumCols());
                     prober.setMaxElements(100);
                     prober.setMaxLookRoot(50);
                     prober.setRowCuts(3);
                     processor.addCutGenerator(&prober);
                 }

    configured_solver = processor.preProcessNonDefault(*cloned_solver,
    2, 10);

    cloned_solver->setHintParam(OsiDoInBranchAndCut, false, OsiHintDo);

    if (!configured_solver)
    {
         delete cloned_solver;
         return status::infeasible;
    }

    configured_solver->setHintParam(OsiDoInBranchAndCut, false, OsiHintDo);

    OsiSolverInterface* configured_clone = configured_solver->clone();

    LP->assignSolver(configured_clone, true /* Kill previous solver */);
    /*-- XXX --*/
    LP->initialSolve();
    LP->branchAndBound();

    int n_cols = cloned_solver->getNumCols();
    processor.postProcess(*LP->solver());

    LP->assignSolver(cloned_solver, true /* Kill previous solver */);
    memcpy(LP->bestSolution(), LP->solver()->getColSolution(), n_cols *
    sizeof(double));

It seems, that we are violating one or two unwritten laws of memory 
management with CBC, but I am at loss as what we are doing wrong here. 
Any help, hints, pointer to documentation, etc. is highly appreciated.

Cheers,
Dirk Eßer
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.coin-or.org/pipermail/cbc/attachments/20140507/0e1eee2b/attachment.html>