[Scip] How to get all transformed and presolved variables?

[Martin Bergner]

Hello Tobias,

> The concept of "active" and "fixed" variables does not have anything to do with pricing. 
> It is really only the output of presolving.
Ok, that is clear.

> In all cases, y will be removed from the set of "active" variables and instead added to 
> the set of "fixed" variables.
This explains a lot.

> The B&C procedure only needs to deal with active variables, because once you have found 
> values for all active variables, the values of fixed variables are determined.
That even more.

> For this reason, many constraints will contain "fixed" variables (usually, these will be 
> aggregated variables rather than variables fixed to a specific value). This does no harm, 
> because SCIP will automatically translate all operations on these variables into 
> equivalent operations on active variables. For example, if you add an aggregated variable 
> to a SCIP_ROW, then SCIP will automatically add the corresponding active variable(s) instead.
Right. I wasn't sure about that. Then I don't need the fixed variables.

Thank you very much for the detailed explanation.

Regards,
   Martin