[Scip] How to find out which constraints were active during the solving process

[Rostislav Stanek]

Dear Gerald,
thank you for your response. Yes I add them via SCIPaddCons(). The idea 
was following: In my model I do not need all constraint which define the 
polytope (it depends on the direction given by the objective function) 
but I do not know which. In my research I would like to minimize the 
number of added constraints without changing the objective value of the 
optimal solution. To do it I would like to generate a statistics showing 
me which constraints were really used and which not (for concrete 
instances). So I mean “active” in the sense “fulfilled with equality” in 
the concrete node in the concrete solved LP. This information I would 
collect during the whole process.
Is it possible to get such a information?
Thanks again.
Best regards
Rostislav

P.S.: Excuse me if I am asking something which should be me clear but I 
was not able to find the answer on the Internet.



Dne 18.4.2013 17:47, Gerald Gamrath napsal(a):
> On 18.04.2013 17:32, Rostislav Stanek wrote:
>> Dear Stefan,
>> thank you very much for your quick response. I tried this solution now
>> but I still get false for all constraints. Is it correct that the
>> function does not ask the SCIP-solver as parameter?
> http://scip.zib.de/doc/html/pub__cons_8h.shtml#a8d003272514fb88ff433a01f0ef9729a
>
> Concerning your other question: What constraints are those which you
> check? How did you create them? Did you add them via SCIPaddCons()?
>
> I'm also not sure whether we mean the same thing with active:
> SCIPconsIsActive() means essentially that the constraint is valid at the
> current node, if you do not add local constraints, that it is a model
> constraint. It has nothing to do with whether the current (LP) solution
> fulfills an inequality as an equality.
>
> What do you want to check and why? Perhaps also the statistics might
> give you some (more general) info?
>
> Best,
> Gerald
>
>
>> Best regards
>> Rostislav
>>
>>
>> Dne 18.4.2013 14:03, Stefan Vigerske napsal(a):
>>> Hi,
>>>
>>> probably you look at the constraints in the original problem, but you
>>> want the one from the transformed problem.
>>>
>>> Try getting the transformed cons first:
>>>      SCIP_CONS* tconstraint;
>>>      SCIP_CALL( SCIPgetTransformedCons(scip, constraint, &tconstraint) );
>>>      if( tconstraint && SCIPconsIsActive(tconstraint) )
>>>      {
>>>        /* found one */
>>>      }
>>>
>>> See also
>>> http://scip.zib.de/doc/html/scip_8h.shtml#ac783997fa88d9b38b4bb7cfc0c101e95
>>>
>>> Best,
>>> Stefan
>>>
>>> On 04/18/2013 01:50 PM, Rostislav Stanek wrote:
>>>> Dear SCIP community,
>>>>
>>>> I have the following problem: I would like to find out which constraints
>>>> were active during the solving process and which did not at all.
>>>>
>>>> Thus I defined an event handler and set the events
>>>> SCIP_EVENTTYPE_FIRSTLPSOLVED and SCIP_EVENTTYPE_LPSOLVED and
>>>> SCIP_EVENTTYPE_NODESOLVED.
>>>>
>>>> Then I call SCIPconsIsActive(constraint) in the method
>>>> SCIP_DECL_EVENTEXEC(EventHandlerLPSolved::scip_exec) and always obtain
>>>> false. (I have references to all constraints (std::vector<SCIP_CONS *>
>>>> &constraints;) in the class).
>>>>
>>>> Am I doing something wrong? Is it possible to get out all constraints
>>>> used during the solving process?
>>>>
>>>> Thank you very much for all hints and tips.
>>>>
>>>> Yours faithfully
>>>> Rostislav Stanek
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