Hello Axel.
Axel Simon wrote:
I'm trying to verify a claim in Halbwachs' paper on factoring polyhedra ("Some ways to reduce the space dimension in polyhedra computations" is the journal version). Specifically, he claims that omitting a common equality relation from the convex hull computation yields not significant speedup. I've tried to run a convex hull calculation, once with the common equalities added and once with the common equalities omitted and found quite a difference in performance.
The difference is in favor of which technique? (This is probably implicit in what you write afterward, but I would like to be sure.)
However, I added the equality as two opposing inequalities. My question: are the two opposing inequalities not immediately turned into one equality by the Constraint class? If not, then this might explain the speed difference I'm seeing.
If I understand correctly, you are asking whether the Constraint_System class immediately turns two opposing inequalities into the corresponding equality. The answer is negative. This kind of simplification only happens (lazily) as part of the conversion/minimization process. Please do not hesitate to come back to us in case I misunderstood the question. All the best,
Roberto