#16014: Improvements to discriminant computation
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Reporter: gagern | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.2
Component: algebra | Resolution:
Keywords: discriminant | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/gagern/ticket/16014 | 66a8c198b7aa57f4567906baf964b30b88f4048f
Dependencies: | Stopgaps:
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Comment (by gagern):
What I implemented so far is a case distinction based on the base ring,
with the new implementation being used for multivariate polynomials and
power series.
I implemented the new code in the existing method for now, in part because
I wasn't sure whether I should add new methods (e.g.
`discriminant_by_resultant` and `discriminant_by_substitution`) or rather
an `algorithm` argument for the `discriminant` method. In the latter case,
the code would stay in that method but be reorganized because the
substitution version could call the resultant version instead of executing
that computation directly.
I'm not sure about this whole `ZeroDivisionError` stuff from #11782 resp.
[http://git.sagemath.org/sage.git/commit/?id=a224fe31d5c960ce56acf2e09e0f408ef92c0899
a224fe3]. When doing the substitution approach, there should be no zero
divisors, so replacing `self` by `poly` in that exception handler is only
for the sake of consistency, but not really required. I guess if I were to
write code for the substitution approach exclusively, I might consider
using `// poly[n]` instead of `* an` to avoid the detour to the fraction
field.
--
Ticket URL: <http://trac.sagemath.org/ticket/16014#comment:3>
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