[PPL-devel] some questions regarding PPL

[Bishoksan Kafle]

On Feb 12, 2016, at 8:03 AM, Roberto Bagnara <bagnara at cs.unipr.it> wrote:

> On 02/11/2016 09:17 PM, Bishoksan Kafle wrote:
>> 
>> On Feb 11, 2016, at 8:05 AM, Roberto Bagnara <bagnara at cs.unipr.it <mailto:bagnara at cs.unipr.it>> wrote:
>> 
>>>> 
>>>> 2. In the article
>>>> (http://bugseng.com/products/ppl/documentation/BagnaraRZH02.pdf),
>>>> you mentioned that poly_hull_assign is different from
>>>> upper_bound_assign for Polyhedra
>>> 
>>> Where exactly do you read that?
>> 
>> Sorry I wanted to ask the difference between poly-hull and convex-hull. Please ignore my previous question.
> 
> The convex polyhedral hull of a set of convex polyhedra P is the smallest
> convex polyhedron that contains all members of P.
> 
> The convex hull of a set of convex polyhedra P is the smallest
> convex set that contains all members of P.
> 
> There exists P such that convex_polyhedral_hull(P) != convex_hull(P).
> For instance, take P = { p1, p2 } where:
> 
>  p1 = { (x, y) in R^2 | x = 0 },
>  p2 = { (x, y) in R^2 | x = 0, y = 1 }.
> 
> We have that (1, 1) belongs to convex_polyhedral_hull(P)
> but (1, 1) does *not* belong to convex_hull(P).

I see your point, but do you mean   
	p2 = { (x, y) in R^2 | x = 1, y = 1 } 
instead of  
	p2 = { (x, y) in R^2 | x = 0, y = 1 }?

thank you
Bishoksan

> Kind regards,
> 
>   Roberto
> 
> -- 
>     Prof. Roberto Bagnara
> 
> Applied Formal Methods Laboratory - University of Parma, Italy
> mailto:bagnara at cs.unipr.it
>                              BUGSENG srl - http://bugseng.com
>                              mailto:roberto.bagnara at bugseng.com