Opened 7 years ago
Closed 7 years ago
#17896 closed defect (duplicate)
Polred during exactification takes too long
Reported by: | gagern | Owned by: | |
---|---|---|---|
Priority: | major | Milestone: | sage-duplicate/invalid/wontfix |
Component: | number fields | Keywords: | qqbar polred performance |
Cc: | Merged in: | ||
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description
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?
Change History (3)
comment:1 Changed 7 years ago by
- Status changed from new to needs_review
comment:2 Changed 7 years ago by
- Milestone changed from sage-6.6 to sage-duplicate/invalid/wontfix
- Status changed from needs_review to positive_review
comment:3 Changed 7 years ago by
- Resolution set to duplicate
- Status changed from positive_review to closed
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This appears to be a duplicate of #15600.