#13312: Polyhedral bugfixes and improvements
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Reporter: mhampton | Owner: mhampton
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.3
Component: geometry | Resolution:
Keywords: polyhedra, polar | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Marshall Hampton, Volker Braun | Merged in:
Dependencies: #11763 | Stopgaps:
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Changes (by {'newvalue': u'Marshall Hampton, Volker Braun', 'oldvalue':
u'Marshall Hampton'}):
* dependencies: => #11763
* author: Marshall Hampton => Marshall Hampton, Volker Braun
Old description:
> The .polar() method of the Polyhedron class is incorrect, currently it
> returns the inversion of the correct answer. Thanks to sarah-marie
> belcastro for pointing this out.
>
> Another bugfix/improvement is adding support for negation, which inverts
> polyhedra. Implementing this revealed that scalar multiplication by
> negative numbers gave incorrect answers for polyhedra with rays.
>
> Finally this adds a convenience function for obtained faces in terms of
> vertex and inequality indices.
>
> Apply
> * [attachment:trac_13312_polyhedral_bugfixes_and_improvements.patch]
New description:
The .polar() method of the Polyhedron class is incorrect, currently it
returns the inversion of the correct answer. Thanks to sarah-marie
belcastro for pointing this out.
Another bugfix/improvement is adding support for negation, which inverts
polyhedra. Implementing this revealed that scalar multiplication by
negative numbers gave incorrect answers for polyhedra with rays.
Finally this adds a convenience function for obtained faces in terms of
vertex and inequality indices.
Apply
* [attachment:trac_13312_neg_polar.patch]
--
Comment:
* rebased on top of #11763
* added commit message
* I'm against the `face_dual_descriptions` method. Never return lists
(mutable), and never return integer indices into internal data structures
if you can help it. Just return the actual object, its the same to Python
(where objects are really references to objects anyways). But I understand
that it would be desirable to access the faces without having to dig
through the face lattice. I've replaced it with a new `faces(dim)` method
that returns the faces in the given dimension. The docstring shows a one-
liner to go from there to the old `face_dual_descriptions` method.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13312#comment:6>
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