[ODE] deterministic simulations

Ricardo Kirkner ricardokirkner at gmail.com
Wed Jun 21 04:59:07 MST 2006

How do you do that ('fix the randoms used in iteration')? Just using
dRandSet? When do you use it, at each iteration step, or at the
beginning of the simulation?



Erwin de Vries wrote:
> To my knowledge ODE is deterministic as is, as long as you fix the randoms 
> used in iteration. I've fixed it up for my own usage a while ago, and it 
> looks like its working perfectly for the things i've done. (Capturing input 
> on a P4, and playing it back on a Athlon worked fine, even in lengthy 
> simulations.)
> Are there FPU specifics that could mess things up?
> Regards,
> Erwin
> ----- Original Message ----- 
> From: "Hampus" <hampus at sxp.se>
> To: "ode-list" <ode at q12.org>
> Sent: Wednesday, June 21, 2006 10:23 AM
> Subject: [ODE] deterministic simulations
>> I know this topic has been up before.
>> I got a reply from another mailing list from a warcraft programmer on
>> how they solved FPU problems for deterministic simulations.
>>> No, I wrote an FPU emulator in C that used the integer unit for all
>> its work. It wasn't pretty. But >by god it worked everywhere, even
>> PowerPC. I only had to drop to assembly for __cntlzw (as >well as an
>> Intel equivalent that used BSR).
>>> Warcraft III utilizes this code; when I last checked, about 5% of
>> our execution time was >dedicated to FPU-less floating point math.
>> Would and FPU emulator be feasable for ODE too?
>> Cheers,
>> Hampa
>> Toribash.com
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