#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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Changes (by {'newvalue': u'Paul Zimmermann', 'oldvalue': ''}):
* keywords: real roots => real roots, sd40.5
* status: new => needs_review
* author: => Paul Zimmermann
Comment:
I found out that reducing the Bernstein coefficients to integers fixes the
two instances of this bug (the one in the description and the one from
comment [comment:8]). Maybe it does not solve all instances, but it is
better than nothing, and it should not hurt to work with integers instead
of rationals.
I suggest reviewers try to find other instances, for example with:
{{{
from sage.rings.polynomial.real_roots import real_roots
R.<x> = ZZ[]
B=10^11
for i in range(10^6):
f = R.random_element((i%13)+1,-B,B)
print f
sys.stdout.flush()
n = len(real_roots(f,seed=-1))
for s in range(1000):
if len(real_roots(f,seed=s))<>n:
print f, n, s
sys.stdout.flush()
raise ValueError
}}}
Paul
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10803#comment:18>
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