Hello,
On Thu, Jun 18, 2009 at 3:56 PM, P M Hillhill@comp.leeds.ac.uk wrote:
What the PPL does also provide is a product domain as a templatic class (Partially_Reduced_Product). By instantiating the templatic arguments to Grid and C_Polyhedron (or NNC_Polyhedron), we can represent something like the Z-Polytopes in Polylib. There is a third templatic argument for this class for specifying a (partial) reduction procedure. If you let us know more exactly what you require for your Loopo interface, we can see if it is already available or if it would be straightforward to add the appropriate feature to the domain.
What I basically do is using Z-polytopes to describe a set of accessed array elements that are reached from a subset (in our case a tile) of a given iteration space. So we basically compute the disjoint union of the image of a number of polytopes under a given affine linear array access function. The result is a (union of) Z-Polytope(s). We then use the Barvinok method for counting the integral number of points in this (Z-)Polytope. We can't use a normal Polytope description, because most access functions are not uni-modular and so we have to deal with Z-Polytopes to keep a correct result for the integral numbers in a disjoint union of those Z-Polytopes.
I just met some researcher from the Thales Group who works on a similar topic and also needs the same Z-Polytope datatype. I think he may contact you soon too about this.
I hope we can find some solution to integral polytope representations, since I believe it is a very valuable tool for modern optimization techniques.
thanks, Michael Classen