Hi Illes, As far as I know, you can't tell Newton to stay within a "region of interest" ( @help-gnu If I'm wrong please correct me). All you can do is to provide the solver with a reasonable starting point. You could also take a look at your function around that region of interest, and see if it behaves nasty. Maybe this could help:
http://en.wikipedia.org/wiki/Newton_iteration#Practical_considerations - Juan Pablo On Oct 30, 2012, at 6:40 AM, "FARKAS, Illes" <[email protected]> wrote: > 2012/10/29 FARKAS, Illes <[email protected]> > >> 2012/10/28 Rhys Ulerich <[email protected]> >> >>>> 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
