## La recherche a retourné 118 résultats

jeu. juin 25, 2020 3:51 am
Forum : Giac
Sujet : sturm vs fsolve
Réponses : 2
Vues : 795

### Re: sturm vs fsolve

Thanks for the hint Bernard!
mar. juin 23, 2020 11:48 am
Forum : Giac
Sujet : sturm vs fsolve
Réponses : 2
Vues : 795

### sturm vs fsolve

Hi, I had the impression that sturm has a better runtime than fsolve when trying to find if a univariate polynomial has a root in an interval. It seems that I am wrong at least for Giac. Has anyone tried experimenting on sturm for a univariate polynomial say of degree 11? Because of my application, ...
lun. avr. 15, 2019 11:09 am
Forum : Giacpy
Sujet : Groebner basis evaluation time is different
Réponses : 5
Vues : 1784

### Re: Groebner basis evaluation time is different

As always, thanks for this enlightening explanation Bernard! Yes, I will try to do benchmark of more polynomial systems (not just katsura9, as you say katsura>11 if this will show the power of giac!) to show the full power of giac. Anyway, now at least I understand. It seems though that in poly.lib ...
sam. avr. 13, 2019 10:05 am
Forum : Giacpy
Sujet : Groebner basis evaluation time is different
Réponses : 5
Vues : 1784

### Groebner basis evaluation time is different

I made a code for Katsura 9 Groebner basis benchmark as follows: from giacpy import giac, gbasis from time import clock, time #katsura n, change n as pleased.. n=9 x=[] ideal=[] for i in xrange(n+1): s= "x" + str(i) x.append(giac(s)) # x_0 + 2\sum_{i=1}^n x_i = 1 f=x[0] for i in xrange(1,n+1): f += ...
mar. févr. 19, 2019 4:34 am
Forum : Xcas - English
Sujet : some problem with determinant of a matrix
Réponses : 4
Vues : 765

### Re: some problem with determinant of a matrix

Thank you Luka and Bernard. I guess I should have known better, I often encounter this and I always forget that at times I should switch to rationals. Maple has similar pecularities when you don't make your float rationals. In case you want to look at this more, I think that when working with less s...
lun. févr. 18, 2019 10:12 am
Forum : Xcas - English
Sujet : some problem with determinant of a matrix
Réponses : 4
Vues : 765

### some problem with determinant of a matrix

Consider the following code m:=matrix[[0,0.425*v2,-0.425,0,0,-d5*l4+d5*l5,d5*l4*v5+d5*v5*l5],[0,0.425,0.425*v2,0,0,-d5*l4*v5-d5*v5*l5,-d5*l4+d5*l5],[0.425,0,0,-0.425*v2,d5*l4*l5*v5-d5*v5,0,0],[-2*v2,0,0,2,2*l4*l5*v5+2*v5,0,0],[0,-2*v2,-2,0,0,2*l4*v5-2*v5*l5,2*l4+2*l5],[0,2,-2*v2,0,0,-2*l4-2*l5,2*l4*...
sam. févr. 16, 2019 11:04 pm
Forum : Giacpy
Sujet : normalizing numeric polynomials
Réponses : 4
Vues : 1097

### Re: normalizing numeric polynomials

This is not giacpy related, I have a similar problem with n>=12: whatever is epsilon or Digits. n:=12:; expand((evalf(10**n,100)*x^2+x)/evalf(10**n,100)) (I put evalf with 100 digits to avoid global Digits or epsilon2zero limitations. Bernard, is there some epsilon2zero use in this division? or is ...
ven. févr. 08, 2019 12:18 pm
Forum : Giacpy
Sujet : normalizing numeric polynomials
Réponses : 4
Vues : 1097

### normalizing numeric polynomials

Consider the following code from giacpy import giac giac("printpow(1)") f=giac("3.02565028105e+042*x^2+x") print (f/f.lcoeff("x")).expand() The above returns 0, but it must return a normalized f (f divided by the coefficient of the monomial with highest degree). Any ideas how to resolve this? Jose
ven. févr. 08, 2019 10:32 am
Forum : Xcas - English
Sujet : getting the coefficient matrix
Réponses : 1
Vues : 403

### getting the coefficient matrix

Hi, Is there an efficient way of getting the coefficient matrix of a system of linear equations eqns with variable vars? I want something like: get_coeff_matrix(eqns,vars) I know I could just loop through the vars and ask for coefficients but I think this is not very efficient (for instance in maple...
mar. janv. 15, 2019 4:49 pm
Forum : Giacpy
Sujet : fsolve and giacpy undef return
Réponses : 3
Vues : 892

### Re: fsolve and giacpy undef return

That is a cause of concern. In any case, Xcas for windows has lapack and blas dependencies precompiled (actually they are cyg librarires, but one can compile directly with lapack and blas dlls in mingwc). I'm not sure what fsolve of giac is dependent on, but its not unreasonable to depend on lapack ...
mar. janv. 15, 2019 10:27 am
Forum : Xcas - English
Sujet : irreducibility check for polynomials
Réponses : 0
Vues : 595

### irreducibility check for polynomials

Hi, I was wondering if there is any irreducibility check (for say integral multivariable polynomials), something like say "is_irreduc"? I can always use "factors" or "factor" to check manually. But there are several reasons why irreducibility check is more useful: 1. Programmatically getting a bool ...
jeu. janv. 10, 2019 4:25 pm
Forum : Giac
Sujet : graph theory commands for Giac
Réponses : 198
Vues : 22410

### Re: graph theory commands for Giac

Hi, Just want to bump here. I don't know the intricacies of your developments and I don't know if it helps. Maybe its worth mentioning that I compile nauty for windows (independent of giac) as a separate dll (in fact I compile with msvc which is rarely possible for math libraries). So I suppose your...
jeu. janv. 10, 2019 4:18 pm
Forum : Giacpy
Sujet : fsolve and giacpy undef return
Réponses : 3
Vues : 892

### fsolve and giacpy undef return

Consider the following code in python using giacpy: from giacpy import giac, fsolve giac("printpow(1)") p1 = giac("-0.001*x2^3-0.09*x0*x2^2+0.317480210394*x2^3+0.251984209979*x0*x2^2-2.8*x0^2*x2-0.1*x2-4.2*x2^2-3.17480210394*x0^2*x2-12.6992084157*x0*x2^2-2.51984209979*x0^3-10.0793683992*x0^2*x2-28*x...
mer. déc. 12, 2018 2:25 pm
Forum : Xcas - English
Sujet : check for absolute irreducibility
Réponses : 1
Vues : 423

### check for absolute irreducibility

Hi,

Is there an absolute irreducibility check in giac/XCas? In maple we have AIrreduc to check absolute irreducibility. For instance I can do:

Code : Tout sélectionner

evala(AIrreduc(x^2+y^2+z^2)); #returns true
evala(AIrreduc(x^2+y^2)); #returns false

Jose
ven. nov. 30, 2018 11:00 am
Forum : Xcas - English
Sujet : arithmetic with residue of polynomials in giac/XCas?
Réponses : 1
Vues : 425

### arithmetic with residue of polynomials in giac/XCas?

Is it possible to use residue ring arithmetic in giac, e.g. instead of Q[x0,x1,x2] I want to do arithmetic in Q[x0,x1,x2]/<f1,f2> for some polynomials f1, f2. I can always artificially induce this, but many things may break if this is not internally encoded (for instance matrix arithmetic with entri...