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Hi John,<br>
<br>
thanks for the reply. I now have a minimal example (for some
definition of minimal, which you can find attached), with which I
can reproduce the access violation. Right now, it seems, that I have
the choice between<br>
<ul>
<li>getting a segfault when trying to clean-up all solvers
instanciated during the program run, or</li>
<li>leaking a solver instance.</li>
</ul>
<p>I am not quite comfortable with option 2, since I don't know, how
much memory is actually leaked in this case, in particular as the
actual application will solve quite a few MIPs sequentially in the
same process. If it were only a couple of bytes per solver
instance, then I am almost willing accept that as "price to pay"
for the preprocessing step. But I don't know the inner workings of
the solvers involved enough to make a judgement here.<br>
</p>
<p>Also, I am still not convinced, that the error isn't entirely in
our own code; right now, though, I don't see anything inherently
wrong. Any help appreciated.<br>
</p>
<p><br>
Cheers,<br>
Dirk Eßer<br>
</p>
<br>
<br>
<div class="moz-cite-prefix">Am 07.05.2014 19:36, schrieb John
Forrest:<br>
</div>
<blockquote cite="mid:536A6F1F.60508@fastercoin.com" type="cite">
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<div class="moz-cite-prefix">Dirk,<br>
<br>
The -cpp was a nice idea - but impossible to keep current - so
something may be broken.<br>
<br>
Try using code from the Cbc/examples driver3.cpp or driver4.cpp
which should give you the same flexibility.<br>
<br>
John Forrest<br>
On 07/05/14 11:18, Dirk Eßer wrote:<br>
</div>
<blockquote cite="mid:536A0873.8030802@web.de" type="cite">
<meta http-equiv="Context-Type" content="text/html;
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Hello,<br>
<br>
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.<br>
<br>
The CbcModel instance is created programmatically<br>
<blockquote><small>OsiClpSolverInterface iface;<br>
CoinPackedMatrix pmx(false, num_columns, num_rows,
num_elements, matrix, columns, starts, lengths);<br>
<br>
iface.setObjSense(-1.0);<br>
iface.loadProblem(pmx, 0, 0, objective, senses, rights, 0);<br>
iface.passInMessageHandler(&printer);<br>
<br>
model_ptr LP(new CbcModel(iface));<br>
... adding stuff via LP->addObjects(...) to declare
integer constraints on variables and a few SOSes ...</small><br>
</blockquote>
Things work fine, if we directly compute a solution without
further preprocessing via<br>
<blockquote><small>LP->initialSolve();<br>
LP->branchAndBound();</small><br>
</blockquote>
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). <br>
<blockquote><small>OsiSolverInterface* original_solver =
LP->solver();<br>
OsiSolverInterface* cloned_solver =
original_solver->clone();<br>
OsiSolverInterface* configured_solver = 0;<br>
<br>
cloned_solver->passInMessageHandler(LP->messageHandler());<br>
cloned_solver->setHintParam(OsiDoInBranchAndCut, true,
OsiHintDo);<br>
<br>
CglPreProcess processor;<br>
<br>
{<br>
CglProbing prober;<br>
prober.setUsingObjective(1);<br>
prober.setMaxPass(3);<br>
prober.setMaxProbeRoot(cloned_solver->getNumCols());<br>
prober.setMaxElements(100);<br>
prober.setMaxLookRoot(50);<br>
prober.setRowCuts(3);<br>
processor.addCutGenerator(&prober);<br>
}<br>
<br>
configured_solver =
processor.preProcessNonDefault(*cloned_solver, 2, 10); <br>
<br>
cloned_solver->setHintParam(OsiDoInBranchAndCut, false,
OsiHintDo);<br>
<br>
if (!configured_solver)<br>
{<br>
delete cloned_solver;<br>
return status::infeasible;<br>
}<br>
<br>
configured_solver->setHintParam(OsiDoInBranchAndCut,
false, OsiHintDo);<br>
<br>
OsiSolverInterface* configured_clone =
configured_solver->clone();<br>
<br>
LP->assignSolver(configured_clone, true /* Kill previous
solver */); /*-- XXX --*/<br>
LP->initialSolve();<br>
LP->branchAndBound();<br>
<br>
int n_cols = cloned_solver->getNumCols();<br>
processor.postProcess(*LP->solver());<br>
<br>
LP->assignSolver(cloned_solver, true /* Kill previous
solver */);<br>
memcpy(LP->bestSolution(),
LP->solver()->getColSolution(), n_cols *
sizeof(double));</small><br>
</blockquote>
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.<br>
<br>
Cheers,<br>
Dirk Eßer<br>
<br>
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<br>
<br>
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