#6237: repeated roots with roots(CDF, multiplicities=False)
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Reporter: ncalexan | Owner: somebody
Type: defect | Status: needs_info
Priority: major | Milestone: sage-4.3.1
Component: basic arithmetic | Keywords: roots CDF multiplicities
Work_issues: | Author: Alex Ghitza
Upstream: N/A | Reviewer:
Merged: |
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Changes (by kcrisman):
* status: needs_review => needs_info
Comment:
This is fine overall, assuming the answer to the following question is
yes.
{{{
if output_complex:
rts = sort_complex_numbers_for_display([L(root) for root
in ext_rts])
else:
rts = [L(root.real()) for root in ext_rts if root.imag()
== 0]
}}}
The first list gives a canonical ordering, so using
{{{
rts_mult.append((rt, mult))
j += mult
}}}
is okay, it won't append the same thing twice. Is that also true for the
second list? I couldn't come up with an example that breaks it, but that
just means I don't know much about how polynomials are represented
internally. At any rate, it should probably be ordered, just to be on the
safe side, if you use that way of finding multiplicities. Does Pari not
compute multiplicities for this? Maxima's implementation does, though
perhaps it doesn't do arbitrary precision. I assume numpy definitely
doesn't do multiplicities.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6237#comment:2>
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