Iterative solver (again) [Was: Re: [ODE] Russ' plans for ODE?]

[Alen Ladavac]

Before this thread (about what ODE needs next) dies, I'd like to bump an
issue that seems to not be stressed enough.

Algorithmic complexity (somewhere around O(n^3) or worse, if I am not
mistaken) of the current direct solver is way too high to be useful for some
complex interactions, and the current StepFast implementation doesn't seem
too stable.

For a start, I was wondering... is there any particular reason why does the
StepFast solver subdivide a step into smaller substeps of shorter length?
Shouldn't it instead reiterate over the same large step, improving the
solution each time?

Alen