[SCIP] implicit integer variables and custom branching

[Georg Brandstätter]

Dear SCIP developers,

I have two questions that I hope you can help me with:

1) How exactly are continuous and implicit integer variables treated 
differently?

I'm currently working with a branch-and-price model where the priced 
variables are continuous. If I leave them continuous, the optimal 
solution I find is fractional. Changing them to implicit integer gives 
me an integral solution (with the same objective value) instead.
Is this because of some cuts that are added by SCIP, or is there 
something else I'm missing?


2) Is there a way to use standard SCIP branching on fractional integer 
variables together with an additional custom branching rule?

I'd like to use Ryan-Foster-style branching in the aforementioned B&P 
model. However, I also have integer variables in my master problem and 
I'd like to only use my custom branching rule if all these master 
variables are already integral. Is there an easy way to do that?

I'm using the object-oriented C++ interface, in case that makes a 
difference.


Thank you,
Georg