[Coin-discuss] OsiClp branchAndBound changes state of model

[Matthew Galati]

Thanks John.

I'll switch to CbcModel and will let you know how it goes.

On Wed, Feb 11, 2015 at 10:33 AM, John Forrest <john.forrest at fastercoin.com>
wrote:

>  Matt,
>
> If line 1 is actually
>
> OsiClpSolverInterface o;
>
> you are in trouble anyway - OsiClpSolverInterface:branchAndBound() was
> only written to satisfy requirements.  OsiCbcSolverInterface is also not so
> good.
>
> So many things will have changed in a CbcModel after search - cutoffs,
> number of nodes etc.  I would set up whatever cuts, heuristics and initial
> model in CbcModel baseModel and then
>
> baseModel.solver()-.addRow();
> CbcModel workingModel = baseModel;
>     workingModel.branchAndBound();
>
> On another of your questions - for flexibility I would pass in a Derived
> message handler (see for example Clp/examples/driver2.cpp) and then do
> exactly what you want in "print".
>
> You can get timings for cut generators, but for strong branching you are
> going to have to use profiling e.g. gprof.
>
> John Forrest
>
>
> On 10/02/15 22:23, Matthew Galati wrote:
>
> The following workflow is not doing what I expected.
>
>  1 OsiClp o;
> 2 o.loadProblem(...)
> 3 o.branchAndBound();
> 4 o.addRow();
> 5 o.branchAndBound();
>
>  After 3, the model seems to be changed - for example, a bunch of columns
> are fixed to 0 and some are fixed to 1. Presumably presolve or the reduced
> model in the tree at the end of solve.
>
>  So, when I add my row, I am no longer working with the original model.
>
>  Bug? Expected behavior?
>
>  How does one go about doing what I want - which is: solve, add a row,
> solve again.
>
>
>
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