[ODE] Mismatching results / non-deterministic behaviour

Klaus Backert Klaus.Backert at t-online.de
Thu Sep 14 06:42:47 MST 2006

Am 14.09.2006 um 09:13 schrieb Hauser Dietmar:

> Can somebody confirm this?
> I've skimmed over the code quickly and there are quite a few rands  
> in there.
> However, so far, the ODE seemed very deterministic to me...
> --
> dIdl

In the Quickstep algorithm there is
and, depending on that, a piece of code for randomly shuffling the  
constraints in the LCP solver for the contact and friction model.

Similar things are going on in the Stepfast algorithm with
(but Stepfast has been superseded by Quickstep).

I don't know exactly, but it looks like there is some random  
influence when stepping the ODE world with Quickstep. And if that is  
true, using Quickstep, results are reproducible only if the random  
seed is reset, as Chris mentioned already.


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