[ODE] test problems?

[Kenneth Holmlund]

Hi,

Russ Smith wrote

> you could try:
> * measure the step speed for N body chain and N body tree. DynaMechs is
>   O(N), the rest are O(N^3) (except i don't know about Darwin2K).


When you say O(N) I suppose you mean Nlog(N)?
On your homepage you say that Havok is O(N^3) and medium speed, while
Vortex/Karma (CM-Labs/MathEngine) is O(N^3) and high speed.
If both are O(N^3), the differences between these two can only be
in the overhead, the prefactor or in the numerics of solving the
DAE:s (optimization, avoiding kinematic loops etc).

Do you have a more detailed motivation of your statement?

There's also something new called Havok Hardcore. Does anyone know the
details about that toolkit? Have they incorporated Ipion into Hardcore?


> * implement highly contacting systems and see how they behave.
>   an example is baraff's part feeder (i'm not sure which paper i saw
>   this in).
> * implement stiff systems, to test the integrator. examples are systems
>   with strong springs or lots of damping.
> 
> note that comparing packages is much more meaningful when it is done
> on real problems, not toy or acedemic problems. so i would recommend
> that you try to build a (very) simple version of your project in
> each package. also note that Mathengine and ODE are roughly the same
> feature-wise, except that Mathengine has more collision primitives,
> more joints, and costs more.



The relations between CML/MathEngine (Vortex & Karma) and ODE are
indeed very, very puzzling...


/Kenneth