#17896: Polred during exactification takes too long
-----------------------------+--------------------------------------------
Reporter: gagern | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.6
Component: number fields | Keywords: qqbar polred performance
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
-----------------------------+--------------------------------------------
The following example comes from comment:27:ticket:16964 via
comment:2:ticket:17886, with syntax for `z` discussed in ticket:17895.
{{{
sage: x,y = polygens(QQ,"x,y")
sage: p1 = x^5 + 6*x^4 - 42*x^3 - 142*x^2 + 467*x + 422
sage: p2 = p1(x=(x-1)^2)
sage: p3 = p2(x=x*y).resultant(p2,x).univariate_polynomial()
sage: p4, = [f[0] for f in p3.factor() if f[0].degree() == 80]
sage: ival = CIF((0.77, 0.78), (-0.08, -0.07))
sage: z, = [r for r in p4.roots(QQbar, False) if r in ival]
sage: %time z.exactify()
}}}
This exactification didn't complete in 6 hours. OK, the polynomial in
question has degree 80, so this is quite some work, but nevertheless
Mathematica can find a minimal polynomial for just this number in 0.2
seconds. There should be some way we can get at least into the less-
than-a-minute range, although I don't know exactly how.
Perhaps we can drop the polred calls in qqbar?
--
Ticket URL: <http://trac.sagemath.org/ticket/17896>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
