[Maxima-bugs] [ maxima-Bugs-696804 ] factor FAILS on polynomial !!!

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Bugs item #696804, was opened at 2003-03-03 14:52
Message generated for change (Comment added) made by macrakis
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
Summary: factor FAILS on polynomial !!!

Initial Comment:
Factor fails to factor a polynomial in two variables.



p:

(23*x^10*y^5 + 82*x^9*y^4 + 80*x^8*y^4 -

28*x^7*y^3 - 47*x^6*y^3 - 74*x^5*y^2 +

28*x^4*y^2 - 74*x^3*y + 25*x^2*y + 21*x - 41)

*

(78*x^10*y^5 + 49*x^9*y^4 + 48*x^8*y^4 +

49*x^7*y^3 + 65*x^6*y^3 - 8*x^5*y^2 +

82*x^4*y^2 - 7*x^3*y - 15*x^2*y - 6*x + 30)



factor(expand(p)) => irreducible



If this is some intentional limitation, it should give some 

sort of warning.  But I don't see why it should be.



This was a polynomial generated randomly using:



product(sum((random(200)-100) * x^i * y^entier(i/2),

                   i,0,10),

           j,1,2)



Sometimes these polynomials factor correctly, but 

mostly they come back as irreducible.



I tried setting Berlefact:false to see if that would make a 

difference, but that causes an internal error 

(POWERSET requires less than two arguments).



I also tried using rat instead of expand to make sure it 

wasn't a multiplication problem rather than a factoring 

problem.



Maxima version: 5.9.0

Maxima build date: 19:10 2/9/2003

host type: i686-pc-mingw32

lisp-implementation-type: Kyoto Common Lisp

lisp-implementation-version: GCL-2-5.0

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>Comment By: Stavros Macrakis (macrakis)
Date: 2003-09-16 09:28

Message:
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Another factor failure:

(34*y^3+987*x*y-23*x^3-1)*(234*x^23*y^45-

978*x^43*y^10+1)

Setting berlefact:false gives error: POWERSET [or a callee] 

requires less than two arguments.

----------------------------------------------------------------------

Comment By: Barton Willis (willisb)
Date: 2003-03-04 16:16

Message:
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Macsyma 2.2 also fails to factor p after it has been

expanded.  Setting berlefact : false didn't make any

difference.



Barton

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