Re: [Help-gsl] solution of 3d quadratic algebraic system

[Sam Mason]

Could you put each variable through a logit transform?  That's the normal
way I'd tend to get appropriate answers.

Either that or use a delta function to give +inf outside your range.

  Sam
On 30 Oct 2012 05:41, "FARKAS, Illes" <address@hidden> wrote:

> 2012/10/29 FARKAS, Illes <address@hidden>
>
> > 2012/10/28 Rhys Ulerich <address@hidden>
> >
> >> > Can you please suggest a fast GSL method / algorithm to find the
> >> solutions
> >> > of a quadratic 3d system of algebraic equations?
> >> >
> >> > In the reduced form all 3 equations have zero on the l.h.s., and on
> the
> >> > r.h.s. there are constant, linear and quadratic terms composed of x1,
> >> x2,
> >> > x3 (the three variables).
> >>
> >> Newton iteration, especially if you provide analytic Jacobian, should do
> >> well here. There may be faster things that can return multiple
> solutions,
> >> however.
> >>
> >> - Rhys
> >>
> >
> > Thanks, I've chosen the hybrid algorithm<
> http://www.gnu.org/software/gsl/manual/html_node/Example-programs-for-Multidimensional-Root-finding.html
> >
> > .
>
>
> Hello,
>
> The 3 variables represent biochemical concentrations normalized to the
> interval [0,1]. Can I tell the solver (or another solver) that it should
> stay inside this interval? I keep receiving solutions outside this
> interval, which are mathematically OK, but biochemically really nonsense.
> Also, with some help I'm ready to read/write the source code.
>
> Many thanks!
>
> Illes
>