#5074: singular factorization over GF(p) need not be a complete factorization
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   Reporter:  was                  |       Owner:  malb                         
              
       Type:  defect               |      Status:  needs_work                   
              
   Priority:  major                |   Milestone:  sage-4.5                     
              
  Component:  commutative algebra  |    Keywords:                               
              
     Author:                       |    Upstream:  Not yet reported upstream; 
Will do shortly.
   Reviewer:                       |      Merged:                               
              
Work_issues:                       |  
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Comment(by was):

 It's definitely still broken.  Note that it isn't broken every single time
 :-):
 {{{

 sage: sage: k.<a> = GF(9)sage: sage: R.<x,y> = PolynomialRing(k)
 sage: sage: h = - (-x^2 - x*y + y^2 - 1)^2 * (x^2*y^2 + y^4 + x^2*y +
 x*y^2 + y^3 - x^2 + x*y + y^2 - 1) * (-x^4 - x^3*y - x*y^3 + y^4 - x^3 +
 x^2*y + x*y^2 - x^2 - x*y - y^2 + x + 1)
 sage: h.factor()
 (-1) * (-x^2 - x*y + y^2 - 1) * (x^2*y^2 + y^4 + x^2*y + x*y^2 + y^3 - x^2
 + x*y + y^2 - 1) * (x^6 - x^5*y + x*y^5 + y^6 + x^5 + x*y^4 - x^4 +
 x^2*y^2 + x*y^3 + y^4 + x^2*y - y^2 - x - 1)
 sage: h.factor()
 (-1) * (-x^2 - x*y + y^2 - 1)^2 * (-x^6*y^2 - x^5*y^3 - x^4*y^4 + x^3*y^5
 + x^2*y^6 - x*y^7 + y^8 - x^6*y - x^4*y^3 + x^3*y^4 + x^2*y^5 + x*y^6 +
 y^7 + x^6 - x^5*y + x^2*y^4 + x^5 + x^3*y^2 - x^2*y^3 - y^5 - x^4 - x^3*y
 + x^2*y^2 - y^4 + x^2*y + x*y^2 + y^3 - x*y - y^2 - x - 1)
 sage: h.factor()
 (-1) * (-x^2 - x*y + y^2 - 1) * (x^8*y^2 - x^7*y^3 + x^6*y^4 - x^5*y^5 +
 x^3*y^7 + x^2*y^8 + x*y^9 + y^10 + x^8*y + x^7*y^2 - x^3*y^6 - x^2*y^7 +
 y^9 - x^8 + x^3*y^5 + x*y^7 - y^8 - x^7 + x^4*y^3 + x^3*y^4 - x^2*y^5 +
 y^7 - x^4*y^2 + x^3*y^3 + x^2*y^4 + x*y^5 - y^6 - x^5 - x^4*y - y^5 + x^4
 - x^3*y + x^2*y^2 + x^3 + x*y^2 - y^3 + x^2 - x*y + x + 1)
 sage: h.factor()
 (-1) * (-x^2 - x*y + y^2 - 1)^2 * (x^2*y^2 + y^4 + x^2*y + x*y^2 + y^3 -
 x^2 + x*y + y^2 - 1) * (-x^4 - x^3*y - x*y^3 + y^4 - x^3 + x^2*y + x*y^2 -
 x^2 - x*y - y^2 + x + 1)
 }}}

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5074#comment:3>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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