I had in mind that it would only be in effect when it detect variable row when I added, but of course the check where it is called in ::add is not here. I'll change.

>I think if n is even you can multiply by the divisor.
>It may be safest to keep it as it is though.


I'm not convinced the way it samples and splits is good anyway, it could do with more refactoring at a later stage.