[SCIP] Branching on optimal solution

[Matheus Ota]

Hi Ambros,

Thank you for replying! Yes, I have read the Constraint Handler and the
Branching Rule tutorials. Let me give more details:

- These are the parameters I chose for the Constraint Handler:
sepapriority: 1000000
enfopriority: 1000000
checkpriority: 1000000
sepafreq: 1
propfreq: -1
eagerfreq: 1
maxprerounds: 0

- And these are the parameters for the Branching Rule:
priority: 200000
maxdepth: -1
maxbounddist: 1

- the SCIP_DECL_CONSENFOLP, SCIP_DECL_CONSENFOPS and SCIP_DECL_CONSCHECK
check if the current solution is a feasible solution (obeys the constraints
and is integer).
I tried to check here only if the solution obeys the constraints, ignoring
the integrality constraint. But my problem remained: in the
SCIP_DECL_BRANCHEXECPS method of the branching rule, the solution that gets
there is made only of integers. So no branching is performed.

- Still, I'm able to solve correctly the problem because other branching is
performed. As shown by the output of SCIPprintStatistics():
Branching Rules    :   ExecTime  SetupTime   BranchLP  BranchExt
BranchPS    Cutoffs    DomReds       Cuts      Conss   Children
  CVRPBranchingRule:       0.00       0.00          0          0
0          0          0          0          0          0
  allfullstrong    :       0.00       0.00          0          0
0          0          0          0          0          0
  cloud            :       0.00       0.00          0          0
0          0          0          0          0          0
  distribution     :       0.00       0.00          0          0
0          0          0          0          0          0
  fullstrong       :       0.00       0.00          0          0
0          0          0          0          0          0
  inference        :       0.00       0.00          0          0
2          0          0          0          0          4
  leastinf         :       0.00       0.00          0          0
0          0          0          0          0          0
  mostinf          :       0.00       0.00          0          0
0          0          0          0          0          0
  multaggr         :       0.00       0.00          0          0
0          0          0          0          0          0
  nodereopt        :       0.00       0.00          0          0
0          0          0          0          0          0
  pscost           :       0.00       0.00          0          0
0          0          0          0          0          0
  random           :       0.00       0.00          0          0
0          0          0          0          0          0
  relpscost        :       3.06       0.00         71          0
0          0        100          0          0         86

I'm kinda lost here. Could you share your thoughts?

Thanks,
Matheus




2018-05-21 16:44 GMT-03:00 Ambros Gleixner <gleixner at zib.de>:

> Hi Matheus,
>
> Have you read the priority section of the "How to add constraint
> handlers?" at
>
> http://scip.zib.de/doc-5.0.1/html/CONS.php
>
> Chances are your CONSHDLR_ENFOPRIORITY is set to "after integrality". Does
> that help?
>
> Best,
> Ambros
>
>
>
>
>
>
> Am 19.05.2018 um 21:10 schrieb Matheus Ota:
>
>> Hi Again,
>>
>> My bad, I made a mistake in my calculations. Actually it is being called
>> in a integer but infeasible solution (that breaks the capacity constraint).
>> But still, from my understanding, branching should be done to fix the
>> integrality constraints, the other restrictions should be fixed by the
>> constraint handler.
>>
>> Thanks,
>> Matheus
>>
>> 2018-05-19 15:17 GMT-03:00 Matheus Ota <matheusota at gmail.com <mailto:
>> matheusota at gmail.com>>:
>>
>>     Hello all,
>>
>>     I'm with a problem in my Branch-and-Cut for the CVRP. I'm currently
>>     having a problem because the Branching Rule that I implemented is
>>     calling the SCIP_DECL_BRANCHEXECPS method, even though the currently
>>     solution is already the optimal one.
>>
>>     I also implemented the SCIP_DECL_CONSENFOLP, SCIP_DECL_CONSENFOPS
>>     and SCIP_DECL_CONSCHECK methods of the Constraint Handler, so that
>>     they check if the current solution is feasible and set result as
>>     SCIP_FEASIBLE or SCIP_INFEASIBLE. Could, someone provide me some
>>     help in this matter?
>>
>>     Thanks,
>>     Matheus
>>
>>
>>
>>
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>>
> --
> Ambros Gleixner, Research Group Mathematical Optimization Methods at Zuse
> Institute Berlin, http://www.zib.de/gleixner
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