[SCIP] Question on symmetry handling with additional plugins

[Marc Pfetsch]

Hi Matheus,

the crucial point is whether and how symmetries are detected. This 
depends on the SCIP version:

- Beginning with the upcoming SCIP 9 your constraint handler needs to 
implement callbacks that give information about the symmetries of your 
constraints to SCIP. Then symmetries can be handled automatically.

- In the "older" SCIP versiosn, your new constraint handler will disable 
symmetry detection, because SCIP does not have any symmetry information 
about your constraint. Thus you would need to add orbitope constraints. 
I do not think that there is an example, but you need a matrix of binary 
variables on which a full symmetry group acts by permuting the columns.

Best

Marc




On 23/02/2024 15:43, Matheus Ota wrote:
> Dear SCIP team,
> 
> I've implemented in SCIP/C++ a branch-and-cut algorithm where the 
> cutting-planes are separated via a constraint handler. I want to add 
> symmetry handling methods on top of this algorithm (like shifted column 
> inequalities). So this leads me to the following question.
> 
>   - Looking at the documentation I can see that I may be able to do this 
> easily by just activating a flag 
> (https://www.scipopt.org/doc/html/SYMMETRY.php 
> <https://www.scipopt.org/doc/html/SYMMETRY.php>). However I wonder if 
> the additional cutting planes that I add iteratively will affect the 
> symmetry handling. Do I need to manually include the orbitope plugin? 
> And if so, how do I do that? Is there any example?
> 
> Thank you for your time,
> Matheus
> 
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