greduce

[yves]

Hi MrMarge

First of all, thank you very much for this great program. I am a french teacher of mathematics and I use it on my PDA (HP Ipaq with WM5) whith my students. I have a problem with the "greduce" function; when I type the following command (extract from Xcas Ref examples):
  greduce(x1^2*x3^2,[x3^3-1,-x2^2-x2*x3-x3^2,x1+x2+x3],[x1,x2,x3],tdeg)
the answer is "\infty x2-1"

Thank you in advance

[MrMage]

What should be the answer?

[yves]

The correct answer is "x2". Anyway the answer to greduce must be a polynomial and cannot comprise infinity.

[MrMage]

A quote by Bernard Parisse, the xcas developer:

The bug is probably related to the non-inclusion of the CoCoA library, which is
responsible for fast Groebner basis reduction (I guess you do not
compile with libcocoa). I do not have time to fix this now (I'm working
on faster gcd for version 0.9.0), but I'll have a look next time I'm
reviewing giac native groebner basis code (which I know to be very bad
and was never a priority since CoCoA was available). If you want to
include CoCoA support for pocketcas, note that you must use a precise
version of CoCoA (see my giac compilation webpage).
It is anyway not really a good idea to use greduce on a platform that
has not much computation power like an ipaq, even if CoCoA support was
enabled.

You may also contact him directly if you wish, or let me give him your email adress.