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## Re: [Help-gsl] Multidimensional root solver

**From**: |
Andrew W. Steiner |

**Subject**: |
Re: [Help-gsl] Multidimensional root solver |

**Date**: |
Thu, 31 Jul 2008 16:52:31 -0400 |

You can rewrite the solver iterate() function to modify the step if it
goes outside of some "allowed" region. Because I run into this
quite a bit, I've done this for O2scl
(c.f. line 780 or so of
http://o2scl.sourceforge.net/o2scl/html/gsl__mroot__hybrids_8h-source.html).
Basically, if the function fails after a proposed step, I shorten the
step by factors
of two until it does not fail anymore. However, I should also warn you that
doing this kind of thing can also make the routine converge less frequently.
HTH,
Andrew
- Andrew Steiner (c.f. O2scl at http://o2scl.sourceforge.net)
On Thu, Jul 31, 2008 at 2:42 PM, Himanshu Chandola
<address@hidden> wrote:
>* Hello everyone,*
>
>* I've been using gsl to solve a set of polynomial equations which are non*
>* linear. There are n equations and n variables. And from the final solution*
>* i've to pick one which satisfies certain constraints. The multidimensional*
>* solver that i use is : gsl_multiroot_fsolver.*
>
>* Now, the thing with multidimensional solver is that I can't give it search*
>* bounds unlike the one dimensional solver. Besides this, since the*
>* multidimensional solver only returns me one root that it finds (the one that*
>* it would find first), there is no way of searching the other roots which*
>* would satisfy the constraints.*
>
>* So, I was thinking whether someone has encountered similar problem before*
>* and figured solving a set of simultaneous nonlinear equations (polynomials*
>* for that matter) when you would want to get all of the solutions. Or at*
>* least the solution satisfying certain constraints (which perhaps might be*
>* achieved by giving search bounds to the solver, but isn't available in the*
>* multidimensional solver).*
>
>* thanks in advance*
>
>
>* Himanshu*
>
>
>* _______________________________________________*
>* Help-gsl mailing list*
>* address@hidden*
>* http://lists.gnu.org/mailman/listinfo/help-gsl*
>