[SCIP] A few questions on SCIP_VARSTATUS

[Rolf van der Hulst]

Hi all,

I am developing a presolving method which is meant to be called late in 
the presolving process, after other presolvers have been called, and 
works on the entire constraint matrix.

I have the following questions,

1. SCIP_VARSTATUS has the values SCIP_VARSTATUS_LOOSE and 
SCIP_VARSTATUS_COLUMN for variables in the transformed problem.
 From the documentation, it is not clear to me how these differ from 
each other. How do these two differ in SCIP?

2. Which status types from SCIP_VARSTATUS are allowed in transformed 
constraints returned by SCIP?

3. What is the correct way, in presolving, to access the (so far) 
presolved constraint matrix formed by all linear constraints of the 
problem? I see a lot of implementations in SCIP call SCIPmatrixCreate(), 
but there is no documentation pointing to this method. Should I use 
this, or are there other alternatives?

4. Is there a method which returns only the set of active variables in 
SCIP? If I understand correctly, the active variables are those that are 
not fixed or aggregated during presolving. (SCIPgetActiveVars() returns 
only the active counterparts)

Best,

Rolf van der Hulst
University of Twente