Opened 4 years ago

Closed 11 months ago

#17251 closed defect (fixed)

Incomplete multivariate factorization

Reported by: jdemeyer Owned by:
Priority: critical Milestone: sage-8.2
Component: factorization Keywords: singular
Cc: jakobkroeker Merged in:
Authors: Frédéric Chapoton Reviewers: Travis Scrimshaw
Report Upstream: Completely fixed; Fix reported upstream Work issues:
Branch: 8ce76ba (Commits) Commit: 8ce76ba086323151cbbd4227d51340749cb7ff2f
Dependencies: Stopgaps:

Description (last modified by jdemeyer)

With sage-6.4.beta6, the following polynomial factorization gives a reducible factor (-a^2 + b^2):

sage: R.<z,a,b> = PolynomialRing(QQ)
sage: N = -a^4*z^8 + 2*a^2*b^2*z^8 - b^4*z^8 - 16*a^3*b*z^7 + 16*a*b^3*z^7 + 28*a^4*z^6 - 56*a^2*b^2*z^6 + 28*b^4*z^6 + 112*a^3*b*z^5 - 112*a*b^3*z^5 - 70*a^4*z^4 + 140*a^2*b^2*z^4 - 70*b^4*z^4 - 112*a^3*b*z^3 + 112*a*b^3*z^3 + 28*a^4*z^2 - 56*a^2*b^2*z^2 + 28*b^4*z^2 + 16*a^3*b*z - 16*a*b^3*z - a^4 + 2*a^2*b^2 - b^4
sage: N.factor()
(-1) * (-a^2 + b^2) * (-z^4*a + z^4*b - 4*z^3*a - 4*z^3*b + 6*z^2*a - 6*z^2*b + 4*z*a + 4*z*b - a + b) * (z^4*a + z^4*b - 4*z^3*a + 4*z^3*b - 6*z^2*a - 6*z^2*b + 4*z*a - 4*z*b + a + b)

This is fixed by #17254.

Change History (9)

comment:1 Changed 4 years ago by jdemeyer

  • Keywords singular added

comment:2 Changed 4 years ago by jdemeyer

  • Description modified (diff)

comment:3 Changed 4 years ago by jdemeyer

  • Description modified (diff)
  • Report Upstream changed from N/A to Completely fixed; Fix reported upstream

comment:4 Changed 4 years ago by jdemeyer

  • Dependencies set to #17254

comment:5 Changed 2 years ago by jakobkroeker

  • Cc jakobkroeker added

Next: add a test.

comment:6 Changed 11 months ago by chapoton

  • Authors set to Frédéric Chapoton
  • Branch set to u/chapoton/17251
  • Commit set to 8ce76ba086323151cbbd4227d51340749cb7ff2f
  • Dependencies #17254 deleted
  • Status changed from new to needs_review

New commits:

8ce76batrac 17251 adding a doctest for factorisation of polynomials

comment:7 Changed 11 months ago by chapoton

  • Milestone changed from sage-6.4 to sage-8.2

comment:8 Changed 11 months ago by tscrim

  • Reviewers set to Travis Scrimshaw
  • Status changed from needs_review to positive_review

LGTM.

comment:9 Changed 11 months ago by vbraun

  • Branch changed from u/chapoton/17251 to 8ce76ba086323151cbbd4227d51340749cb7ff2f
  • Resolution set to fixed
  • Status changed from positive_review to closed
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