[ODE] deterministic simulations

[Erwin de Vries]

I've modified the dRand functions not to use the static seed variable 
anymore, and simply take a parameter instead. Your option would also work, 
but i needed this to make ODE able to handle multithreading.

Regards,
Erwin

----- Original Message ----- 
From: "Ricardo Kirkner" <ricardokirkner at gmail.com>
To: "Erwin de Vries" <erwin at vo.com>
Cc: "ode-list" <ode at q12.org>
Sent: Wednesday, June 21, 2006 1:59 PM
Subject: Re: [ODE] deterministic simulations


> 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?
>
> regards
>
> ricardo
>
> 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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>>>
>>
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>