#10140: Base sage.geometry.cone on the Parma Polyhedra Library (PPL)
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Reporter: vbraun | Owner: mhampton
Type: enhancement | Status: needs_info
Priority: major | Milestone: sage-4.7
Component: geometry | Keywords: ppl
Author: Volker Braun | Upstream: N/A
Reviewer: Andrey Novoseltsev | Merged:
Work_issues: |
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Comment(by novoselt):
Replying to [comment:25 vbraun]:
> I think its easier to just go with PPL's ordering. It also matches the
behaviour of the Polyhedron class which will reorder generators. We
already have the `Cone_of_fan` to keep track of ray orderings with respect
to some particular enumeration of rays.
It is very annoying to deal with several objects that are "the same" but
are slightly different, e.g. have different ordering of rays. Also, users
may have some ideas about "convenient order" and provide rays in it: if I
create the first quadrant as `Cone([(1,0), (0,1)])`, I expect that the
first ray will be the first basis vector and the second - the second, as
it was given. Remembering to add `check=False` is annoying. Making
`check=False` default is very dangerous, as I have learned the hard way. I
really really want to preserve the order whenever possible. I even plan to
add the possibility to manually provide the order of facets and points for
lattice polytopes, since it will allow convenient work with Cayley cones
and polytopes of nef-partitions - they are easy to create with current
code, but keeping track of face duality is very ugly.
I will be very happy to add the sorting myself on top your patch, fixing
all affected doctests, so pleeease let me do it ;-)
> I can add back in a check that the polyhedron is really a cone, perhaps
tomorrow. Generating a Cone from a Polyhedron is only for convenience, I
don't see any need to make it fast. All actual computations are now done
with PPL.
I am more concerned about validity checks than performance here. And I am
also happy to do the necessary copy-pasting here. So you don't really have
to do anything, just say that you are OK with it!
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10140#comment:26>
Sage <http://www.sagemath.org>
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