#10803: critical bug in real_roots
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Reporter: zimmerma | Owner: jason, jkantor
Type: defect | Status: new
Priority: blocker | Milestone: sage-4.6.2
Component: numerical | Keywords: real roots
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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This was reported on http://groups.google.com/group/sage-
support/msg/6a7c93ad16b892bf:
{{{
sage: from sage.rings.polynomial.real_roots import real_roots
sage: x = polygen(QQ)
sage: f = 2503841067*x^13 - 15465014877*x^12 + 37514382885*x^11 -
44333754994*x^10 + 24138665092*x^9 - 2059014842*x^8 - 3197810701*x^7 +
803983752*x^6 + 123767204*x^5 - 26596986*x^4 - 2327140*x^3 + 75923*x^2
+ 7174*x + 102
sage: len(real_roots(f)), len(real_roots(f,strategy='warp'))
(11, 13)
}}}
It seems different seeds give different numbers of roots:
{{{
sage: len(real_roots(f,seed=1))
11
sage: len(real_roots(f,seed=3))
13
}}}
I mark this as blocker since counting properly the number of real
roots of a polynomial is a very basic thing for a computer algebra system.
Paul
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10803>
Sage <http://www.sagemath.org>
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