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/686 http://trac.sagemath.org/sage_trac/ticket/4022 http://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] --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
