#13183: Implement index(cone) for fan morphisms
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Reporter: novoselt | Owner: mhampton
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.2
Component: geometry | Resolution:
Keywords: toric | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Andrey Novoseltsev | Merged in:
Dependencies: #12544 | Stopgaps:
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Changes (by novoselt):
* status: new => needs_review
* dependencies: => #12544
Comment:
OK, ready for review, with infinity for the infinite index, otherwise it
is confusing. It also turned out that old implementation was not generic
enough to handle sublattices, I've added a workaround using the index over
the origin, which is mathematically exactly the same. More general code is
also added to `_Cone_from_PPL` and `normalize_rays`, which turned out to
be quite a bit slower than existing one. So I made sure that we still use
the old route when it is sufficient, in particular I don't see any speed
regression on testing sage/geometry and sage/schemes/toric (by the way
Volker - thanks for the idea to move toric files to a separate folder -
very convenient for testing!).
The second patch is somewhat optional, but I propose to include it: since
now we mostly deal with matrices whose rows (and not columns) are ray
generators, it is more natural. Code is the third hunk, the rest is
doctest adjustment due to a different choice of generators.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13183#comment:7>
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