Opened 11 years ago

Closed 11 years ago

#10279 closed defect (fixed)

Bug in factor of polynomials over number fields

Reported by: lftabera Owned by: davidloeffler
Priority: major Milestone: sage-4.6.2
Component: number fields Keywords: pari, factor, number field
Cc: jdemeyer Merged in: sage-4.6.2.alpha2
Authors: Jeroen Demeyer Reviewers: Luis Felipe Tabera Alonso
Report Upstream: Fixed upstream, but not in a stable release. Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Status badges

Description (last modified by jdemeyer)

Bug raised in sage-devel by Niels Lubbes

http://groups.google.com/group/sage-devel/browse_thread/thread/33aa40a7685f37aa/d6a6230ee023fd06?show_docid=d6a6230ee023fd06

 sage: R = PolynomialRing( QQ, var( 't' ), order = 'lex' ) 
 sage: t = R.gens()[0] 
 sage: f = t^4 - t^2 + 1 
 sage: T = NumberFieldTower( [f], 'a0' ) 
 sage: R1 = R.change_ring( T ) 
 sage: a0 = T.gens()[0] 
 sage: t = R1.gens()[0] 
 sage: poly = t^3 + (-4*a0^3 + 2*a0)*t^2 - 11/3*a0^2*t + 2/3*a0^3 - 4/3*a0 
 sage: poly.factor() 
 (t - 2*a0^3 + a0) * (t^2 + (-2*a0^3 + a0)*t - 2/3*a0^2) 
 sage: fact = poly.factor()[1][0] 
 sage: fact.factor() 
 (t - 4/3*a0^3 + 2/3*a0) * (t - 2/3*a0^3 + 1/3*a0) 

As Jeroen Demeyer points, it is a bug in Pari.

 gp> t; nf = nfinit(a^4 - a^2 + 1); 
 gp> poly = t^3 + (-4*a^3 + 2*a)*t^2 - 11/3*a^2*t + 2/3*a^3 - 4/3*a 
 %1 = t^3 + (-4*a^3 + 2*a)*t^2 - 11/3*a^2*t + (2/3*a^3 - 4/3*a) 
 gp> F = nffactor(nf, poly) 
 %2 = 
 [t + Mod(-2*a^3 + a, a^4 - a^2 + 1) 1] 
 
 [t^2 + Mod(-2*a^3 + a, a^4 - a^2 + 1)*t + Mod(-2/3*a^2, a^4 - a^2 + 1) 1] 
 
 gp> nffactor(nf, F[2,1]) 
 %3 = 
 [t + Mod(-4/3*a^3 + 2/3*a, a^4 - a^2 + 1) 1] 
 
 [t + Mod(-2/3*a^3 + 1/3*a, a^4 - a^2 + 1) 1] 

The fix for this bug is in #10430, the attached patch simply adds a doctest.

Attachments (1)

10279_doctest.patch (1.1 KB) - added by jdemeyer 11 years ago.

Download all attachments as: .zip

Change History (13)

comment:2 Changed 11 years ago by jdemeyer

  • Cc jdemeyer added
  • Component changed from factorization to number fields
  • Milestone set to sage-4.6.1
  • Owner changed from tbd to davidloeffler
  • Report Upstream changed from Reported upstream. Little or no feedback. to Reported upstream. Developers acknowledge bug.

comment:3 Changed 11 years ago by jdemeyer

  • Report Upstream changed from Reported upstream. Developers acknowledge bug. to Fixed upstream, but not in a stable release.

comment:4 Changed 11 years ago by jdemeyer

  • Milestone changed from sage-4.6.1 to sage-duplicate/invalid/wontfix
  • Status changed from new to needs_review

See #10430

comment:5 follow-up: Changed 11 years ago by davidloeffler

  • Milestone changed from sage-duplicate/invalid/wontfix to sage-4.6.2

I suggest we keep this ticket open until the new Pari is in, and then we can add a doctest to prove that it is fixed. Otherwise there is a danger that we forget to add such a doctest and the bug reappears at a later date.

comment:6 in reply to: ↑ 5 Changed 11 years ago by jdemeyer

  • Authors set to Jeroen Demeyer
  • Description modified (diff)

Replying to davidloeffler:

I suggest we keep this ticket open until the new Pari is in, and then we can add a doctest to prove that it is fixed. Otherwise there is a danger that we forget to add such a doctest and the bug reappears at a later date.

Agreed!

comment:7 Changed 11 years ago by lftabera

  • Reviewers set to Luis Felipe Tabera Alonso
  • Status changed from needs_review to positive_review

This is a trivial doctest patch. The patch applies cleanly and adds a relevant doctest. Once #10430 is merged this will go along. Positive review.

comment:8 Changed 11 years ago by jdemeyer

  • Merged in set to sage-4.6.2.alpha1
  • Resolution set to fixed
  • Status changed from positive_review to closed

comment:9 Changed 11 years ago by jdemeyer

  • Merged in sage-4.6.2.alpha1 deleted
  • Resolution fixed deleted
  • Status changed from closed to new

comment:10 Changed 11 years ago by jdemeyer

  • Status changed from new to needs_review

comment:11 Changed 11 years ago by jdemeyer

  • Status changed from needs_review to positive_review

Changed 11 years ago by jdemeyer

comment:12 Changed 11 years ago by jdemeyer

  • Merged in set to sage-4.6.2.alpha2
  • Resolution set to fixed
  • Status changed from positive_review to closed
Note: See TracTickets for help on using tickets.