[Coin-discuss] OsiClp branchAndBound changes state of model

[John Forrest]

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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