[Bug-gsl] Re: [bug #30947] Please, include fixed step size control object for ode suite

[Sergey B Kirpichev]

On 9/3/10, Tuomo Keskitalo <address@hidden> wrote:
>  one important reason for the evolve level functions is to allow for variable
>  step size.
Adaptive step size control.  Why don't consider the *evolve_apply with
fixed step as just a special case?

> If you really require a fixed step size for the stepper level, then
>  you can use the for loop around step_apply function shown in the manual.
Of cource, I can (it was noted in bugreport).  Sometimes it's just not
convinient to use _different loops_ for fixed and variable step sizes.

>  Also, I'm afraid that using your cfxd may not guarantee the use of a fixed
>  step size; also evolve_apply can change the step length, so you might have to
>  have a function something like "evolve_apply_fixed_step_size" to do the job.

Why?  fc_control_hadjust() always returns GSL_ODEIV_HADJ_NIL - there
is no reason to change step size.