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

[FARKAS, Illes]

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