Multi-sphere versus ellipsoid

Hi everybody,

I am trying to model a cylinder-like shape with a high length-to-diameter ratio.

The multi-sphere particle could look like this: ooooooo
So, the model would include a huge number of spheres, when I try to model several thousand of those particles.

As far as I know, liggghts also supports the application of ellipsoids in granular models, via the ASPHERE package.

With respect to computational time:
- Would it be a good idea to use an ellipsoid instead of the multi-sphere approach?
- Is there a limit, when contact detection between ellipsoids is always (or likely) to be quicker than that for a certain number of spheres?

With respect to modelling in liggghts:
- Can I add different ellipsiod shapes at the same time? (different factories would be fine)
- Can the ellipsoid-ellipsoid contact include rolling friction?

Thank you very much in advance.

Best regards,
MiRa