#20243: Count real roots of polynomials using Sturm sequences
-------------------------------------+-------------------------------------
Reporter: kedlaya | Owner: kedlaya
Type: enhancement | Status: needs_work
Priority: minor | Milestone: sage-7.2
Component: algebra | Resolution:
Keywords: polynomials, | Merged in:
root-counting, days71 | Reviewers:
Authors: Kiran Kedlaya | Work issues:
Report Upstream: N/A | Commit:
Branch: | f932dd3fef7fcf36a8ddd2a9f07cb3f4ae69bc33
u/kedlaya/count_real_roots_of_polynomials_using_sturm_sequences| Stopgaps:
Dependencies: #20256 |
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Comment (by kedlaya):
I'm not sure checking the base ring is the right approach; one use case
that was already suggested above is a polynomial over CC which happens to
have real coefficients. One option is to attempt the coercion by calling
{{{self.change_ring(RR)}}} and discarding the result (allowing a
{{{TypeError}}} through if it comes up). Working on the PARI side
eliminates this particular case:
{{{
sage: u = CC(1)
sage: u.parent()
Complex Field with 53 bits of precision
sage: pari(u)
1.00000000000000
sage: pari(u).type()
't_REAL'
}}}
Thoughts?
--
Ticket URL: <http://trac.sagemath.org/ticket/20243#comment:29>
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