[ODE] Mismatching results / non-deterministic behaviour

[Hauser Dietmar]

Ah, I see!
That explains a lot of things I've experienced with repeating steps 
(or trying to at least) actually! ;) 

That also explains, why results were the same, when being run on 
different machines, because the ODE random number was never 
initialised and therefor using the same predefined seed.

Thanks,
dIdl


> -----Ursprüngliche Nachricht-----
> Von: ode-bounces at q12.org [mailto:ode-bounces at q12.org] Im 
> Auftrag von Klaus Backert
> Gesendet: Donnerstag, 14. September 2006 15:43
> An: ode at q12.org
> Betreff: Re: [ODE] Mismatching results / non-deterministic behaviour
> 
> 
> 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
> #define RANDOMLY_REORDER_CONSTRAINTS 1
> 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
> #define RANDOM_JOINT_ORDER
> (but Stepfast has been superseded by Quickstep).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.
> 
> Cheers
> Klaus
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