Le forum de XCAS

Thanks for the tip about polynome. Nevertheless,_gbasis still gives me "not found". I am not sure if this is because of my visual studio build. I will investigate this more as I do not know exactly where the problem lies. The same code in giacpy shows no problem: from giacpy import giac, gbasis from...

I have written a sample code testing gbasis on katsura9 (or katsura10 depending on definition) polynomials system. #include <config.h> #include <giac.h> using namespace std; using namespace giac; int main() { giac::context ct; vecteur x; vectpoly ideal; stringstream sstr; int n=9; //variable vector ...

Hi, Is there anywhere I could see a minimal example of how I can compute groebner basis using giac in C++? For instance suppose I have a vecpoly consisting of generator of an ideal (say some katsura polynomial system) and now I want to use gbasis. I see that in solve.cc there is a method called giac...

Thanks. Regarding the ntl issue and windows I can remind everyone about the link of the discussion (crash in factor if giac is linked with ntl in windows): http://xcas.e.ujf-grenoble.fr/XCAS/viewtopic.php?f=3&t=1901 What if I am able to compile giac with mpir, will the lack of ntl still make factor ...

Well, there is a confusion in the meaning of t, your t is alpha=rootof([[1,0],[1,0,-3,1]]), rootof(P,M) where P and M are list polynomials means P(alpha) where M(alpha)=0 (M irreducible). The last command of Frederic is the list of factors of t^3-3t+1, i.e. t+(-alpha), t+(-alpha^2+2), t+(alpha^2+al...

Hi Frederic, Thank you for your answer. I do not understand the output of rootof, I do not see [t,t^2-2,-t^2-t+4] in the output of your sample code. Could you explain a bit? More generally, if f is a polynomial over Q (of arbitrary degree) such that the splitting field of f is Q(a) for some root "a"...

Hi, I want to know how to access some member variable of a pari type that comes out of giac/giacpy. Here is an example: from giacpy import giac giac("printpow(1)") giac("pari()") nfinit = giac("nfinit") galoisinit = giac("galoisinit") f = giac("t^3-3*t+1") #splitting field has primitive element whic...

Hi Frederic, Thanks for the update. Is there already a fix on matrix initialization (deep copy vs. shallow copy of matrix elements) in this version of giacpy? I am talking about having to initilaize matrices by mat = matrix(3,3) instead of mat = matrix(3,3,'(u,v)->0')) because of a bug in initializa...

Oh nice. So if I put in the ordering as a third parameter I actually get the leading term (not only the leading coefficient) with respect to the that ordering. I couldn't have guessed (I don't think it was also in the manual, but I have an older pdf version of the manual). Thanks and sorry for the d...

Hi, I was wondering if there is really no way to get leading term monomial list from a list of (multivariate) polynomials such as? Or apply monomial ordering (of certain ordering type, e.g. plex, tdeg etc.) to a certain polynomial I am sure these features (maybe hidden internally) exists in giac but...

Hi, I noticed the following problem from giacpy import degree degree("x1**2") degree("x**2") The first will return 0, the second will return 2. Although giac recognizes the expressions properly i.e. when doing arithmetic the indeterminate x1 will behave as it should. This behaviour also exists in Xc...

Hi, What is the easiest (and not very slow) way to get a list of monomials of a polynomial. For instance if I have 3x*y+3x^2+y I want the list [3x*y,3x^2,y]. I can write a code that takes the total degree and walks through all possible monomial not exceeding this degree, but this will not be efficie...

Hi, I just want to report that gramschmidt is missing in giacpy. Edit: I got it working using the same trick Frederic taught me for using randseed (basically calling it using giac, so you can enclose "gramschmidt" in giac instead of Pygen) from giacpy import Pygen, ranm gramschmidt = Pygen("gramschm...

Thanks Frederic. This worked. Now I can rely on the randomizer.

Hi Frederic,

I would like to point your attention to the following post:
http://xcas.e.ujf-grenoble.fr/XCAS/view ... f=4&t=1968

I think you answered my other posts but this post got lost between other posts. I believe that randseed is behaving differently than it should in giacpy.

Jose