[SCIP] Looking for example how to express symmetry groups

[Johann-Tobias Schäg]

> Marc Pfetsch <pfetsch at mathematik.tu-darmstadt.de> hat am 12.06.2025 14:08 CEST geschrieben:
> 
>  
> Dear Johann-Tobias,
> 
> the main workhorse for symmetry handling is prop_symmetry. This 
> propagator stores the symmetry information that you are probably 
> interested in. It stores the generators of the permutation group in 
> dense format. 

Is that dense format documented somewhere?

> 
> An explanation of the symmetry handling capabilities is available in the 
> SCIP Release Reports (see the SCIP webpage).
> 
> Note that SCIP can also handle symmetries on non-binary variables.

Neat, the docs i linked only mentioned binary variables only so i inferred that.

> 
> I hope that these pointers give you enough information. Otherwise, we 
> would need more specific questions.

Is there an example where the user provides a description of some/all symmetries of a problem? (possibly in the C API).

Sincerely,
Johann-Tobias

> 
> Best
> 
> Marc
> 
> 
> On 12/06/2025 11:58, Johann-Tobias Schäg wrote:
> > I am aware that there are mutliple ways to handle symmetries in SCIP
> > https://www.scipopt.org/doc/html/cons__orbisack_8h.php 
> > <https://www.scipopt.org/doc/html/cons__orbisack_8h.php>
> > https://www.scipopt.org/doc/html/cons__orbitope_8h.php 
> > <https://www.scipopt.org/doc/html/cons__orbitope_8h.php>
> > https://www.scipopt.org/doc/html/cons__symresack_8h.php 
> > <https://www.scipopt.org/doc/html/cons__symresack_8h.php>
> > All those are for binary variables.
> > I occasionally encounter 0-1 ILP which have symmetries so large that 
> > SCIP fails to (fully) detect them. I asked on the OR stack exchange 
> > whether there is a standardized format for symmetry groups: 
> > https://or.stackexchange.com/questions/13187/are-there-existing-formats-to-express-symmetries-between-variables-in-milp?noredirect=1#comment28418_13187 <https://or.stackexchange.com/questions/13187/are-there-existing-formats-to-express-symmetries-between-variables-in-milp?noredirect=1#comment28418_13187> and was pointed towards SCIP being potentially interesting for that.
> > Is there some examples which use those constraints handlers?
> > The documentation i linked above is to dense for me to make sense of.
> > Sincerely,
> > Johann-Tobias Schäg
> > 
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