#10803: critical bug in real_roots
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Reporter: zimmerma | Owner: jason, jkantor
Type: defect | Status: needs_review
Priority: critical | Milestone: sage-5.1
Component: numerical | Resolution:
Keywords: real roots, sd40.5 | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Paul Zimmermann | Merged in:
Dependencies: | Stopgaps:
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Comment (by zimmerma):
I've worked a little more on this. It seems the {{{_count_variations}}}
function is called with a wrong {{{usign}}} (sign in x=1 if I understand
correctly) in the following case:
{{{
enter _count_variations, self= <IBP: ((67412088, 41929949, 16504578,
-2435470, -4640) + [0 .. 18683)) * 2^-10 over [3921/16384 .. 8017/32768];
usign 1; level 3; slope_err [-41131.637071203295 .. 41131.637071203295]>
}}}
and then returns 2 changes of sign whereas there is evidently only one in
the coefficients.
Paul
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10803#comment:20>
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