#5921: [with patch, needs review] factoring integer polynomials does not factor
the content
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Reporter: cremona | Owner: tbd
Type: defect | Status: new
Priority: major | Milestone: sage-4.0
Component: algebra | Keywords:
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Comment(by AlexGhitza):
Yes, the problem is in {{{f.roots()}}} for a polynomial f with integer
coefficients. The code used to just run {{{f.factor()}}}, but of course
now if the content is a huge integer it's gonna take a while for the
factoring to finish. There's a doctest in the sage library that runs into
precisely this problem now, since it's an illustration of RSA and has huge
coefficients (and a huge content) floating around. However, you don't
care about the content if you just want the roots of the polynomial.
So the attached patch makes {{{roots()}}} divide by the content first,
then call {{{factor()}}}. It also adds a warning to this effect in the
docstrings of the two {{{factor()}}} methods.
I'm happy with John's patch, so if someone reviews my patch we're done.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5921#comment:6>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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