#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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Changes (by novoselt):
* cc: nthiery (added)
Comment:
Hi Volker, I have started work on the reviewer patch, so please don't
change the attached ones. (They don't seem to apply cleanly anymore, but I
will take care of it.)
Hi Nicolas, I am adding you to the cc field in case you have further
comments on the ray order ;-)
I have realized that
* I mostly care about preserving the order of rays only if they are
already the minimal generating rays of a strictly convex cone and
* implementing this does not introduce any performance penalty: once we
have constructed the PPL object, we know if the cone is strictly convex or
not and we can just compare the number of its rays with the input - it
these numbers are the same, then we can use the input rays as minimal
generators directly.
So instead of `keep_order` I would like to add the above check.
Advantages:
1. It is convenient if the user cares about the ray order, e.g. for
constructing an affine toric variety straight from a cone, when one may
want to associate particular variable names with particular rays.
1. It allows easy writing of doctests which explicitly show rays without
worrying that the order will change in future releases and a bunch of
trivial adjustments will be required.
1. It constructs the same cones with `check=True` and `check=False`
options in cases when it is indeed OK to use `check=False` option.
1. It is a bit more intuitive to the user and in particular nice for
tutorials and live demonstrations.
1. It makes me happy ;-)
Frankly, I cannot really think of any disadvantages...
So - can I proceed and implement this?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10140#comment:39>
Sage <http://www.sagemath.org>
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