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Re: GSL ode-initval development
At Sun, 31 Aug 2008 10:25:26 +0300,
Tuomo Keskitalo wrote:
> I have been writing a non-linear equation solver based on a modified
> Newton iteration method, and a question about failures has come up. What
> value should the non-linear equation solver return to the stepper (and
> from there to user) in the case that the method reaches a maximum number
> of Newton iterations and therefore fails? GSL_CONTINUE or GSL_FAILURE or
> something else?
I'd suggest GSL_FAILURE to start with. Hopefully the solver won't fail
that often.
> which values of variables y should a stepper which uses step doubling
> for error estimation return: The values from the single step or the
> values from two half steps? You would expect to get the values of single
> step from "a stepper", but the values from two half steps should be more
> accurate, and they are available.
The final value of y should come from the two half steps as they are
more accurate. See rk4.c for an example and the error estimate.
--
Brian Gough