singular error

[John Cremona]

The code below causes a singular error, in 5.1 and 5.2 it's
"RuntimeError: zz_pContext: p must be > 1" while in 5.3.rc1 it's
"RuntimeError: Floating point exception". Has this been seen before,
or is a new ticket required?

John

PS If you can tell what the computation is about, you get a prize.

Z = ZZ
Qu.<u> = FractionField(PolynomialRing(Z,'u'))
Qt.<t> = FractionField(PolynomialRing(Z,'t'))
Qj.<j> = FractionField(PolynomialRing(Z,'j'))
t2u = Hom(Qt,Qu)(27/(u^3 - 1))
j2t = Hom(Qj,Qt)((t + 3)^3 * (t + 27)/t)
X = polygen(QQ)
Q3.<z> = NumberField(X^2-X+1)
ju = t2u(j2t(j)) # j as a function of u
nju = ju.numerator()
dju = ju.denominator()
Q3xy.<x,y> = Q3[]
ffQ3=(nju(x)*dju(y)-nju(y)*dju(x)).factor()

/home/jec/sage-5.3.rc1/local/lib/python2.7/site-packages/sage/rings/polynomial/multi_polynomial_libsingular.so
in sage.rings.polynomial.multi_polynomial_libsingular.MPolynomial_libsingular.factor
(sage/rings/polynomial/multi_polynomial_libsingular.cpp:25414)()

RuntimeError: Floating point exception

[Jeroen Demeyer]

On 2012-09-07 15:24, John Cremona wrote:
> The code below causes a singular error, in 5.1 and 5.2 it's
> "RuntimeError: zz_pContext: p must be > 1" while in 5.3.rc1 it's
> "RuntimeError: Floating point exception". Has this been seen before,
> or is a new ticket required?

It seems to be fixed by #13237. I get the answer

sage: ffQ3
(27) * (x - y) * (x + (z)*y) * (x + (-z + 1)*y) * (x*y + (z)*x + (z)*y +
(-2*z + 2)) * (x*y + (-z + 1)*x + (z)*y - 2) * (x*y + (z)*x + (-z + 1)*y
- 2) * (x*y - x + (-z + 1)*y + (-2*z + 2)) * (x*y + (-z + 1)*x - y +
(-2*z + 2)) * (x*y + (z)*x - y + (2*z)) * (x*y - x + (z)*y + (2*z)) *
(x*y + (-z + 1)*x + (-z + 1)*y + (2*z)) * (x*y - x - y - 2)

[John Cremona]

Thanks -- I have not seen 5.4.beta0 announced, but will get hold of it.

John

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[Jeroen Demeyer]

On 2012-09-07 16:48, John Cremona wrote:
> Thanks -- I have not seen 5.4.beta0 announced, but will get hold of it.

It hasn't been released yet, but it's essentially stable. You can go
ahead and use it, but keep in mind you won't have an official version
and you should not report bugs for it.