cool, thanks a lot !
On Sep 16, 6:42 pm, Martin Albrecht <[EMAIL PROTECTED]>
wrote:
> On Tuesday 16 September 2008, Pierre wrote:
>
>
>
> > What did you put in J ? in fact, the following already produces the
> > bug (sorry for not trying earlier, i thought i did try and there was
> > no bug... must have changed a little something):
>
> > sage: k= CyclotomicField(3, "w")
> > sage: A= PolynomialRing(k, ["y9", "y12", "y13", "y15"])
> > sage: y9, y12, y13, y15= A.gens()
> > sage: J= [ y9 + y12]*A; J.groebner_basis()
> > sage: J.reduce(y9 - y12)
> > -2*y12
> > sage: J.reduce(y13*y15)
> > y13*y15
> > sage: J.reduce(y13*y15 + y9 - y12)
> > y13*y15 + y9 - y12
>
> > Which is odd. I had read J.reduce?, it seems to indicate that the
> > function returns what i would also call the reduction, but that is
> > linear. So I think this is a bug.
>
> Luckily (because we can fix it)/ unfortunately (because I'm probably to blame)
> it seems like a bug in our pexpect interface to Singular.
>
> First, this is vanilla 3.1.2.rc2:
>
> sage: k.<w> = CyclotomicField(3)
> sage: A= PolynomialRing(k, ["y9", "y12", "y13", "y15"])
> sage: A.inject_variables()
> sage: J= [ y9 + y12]*A
> sage: J.groebner_basis()
> sage: J.reduce(y13*y15 + y9 - y12)
> y13*y15 + y9 - y12
>
> This is 3.1.2.rc2 with
>
> http://trac.sagemath.org/sage_trac/ticket/686http://trac.sagemath.org/sage_trac/ticket/4022http://trac.sagemath.org/sage_trac/ticket/4021
>
> applied:
>
> sage: k.<w> = CyclotomicField(3)
> sage: A= PolynomialRing(k, ["y9", "y12", "y13", "y15"])
> sage: A.inject_variables()
> sage: J= [ y9 + y12]*A
> sage: J.groebner_basis()
> sage: J.reduce(y13*y15 + y9 - y12)
> y13*y15 - 2*y12
>
> so quite obviously we fail to tell Singular via pexpect to perform tail
> reduction while in the libSingular wrapper we do tail reduction.
>
> I'll look into it. Btw. reduction to zero should still work, since that
> doesn't require tail reduction.
>
> Cheers,
> Martin
>
> --
> name: Martin Albrecht
> _pgp:http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8EF0DC99
> _www:http://www.informatik.uni-bremen.de/~malb
> _jab: [EMAIL PROTECTED]
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