Re: Saving and reading rng state from (ascii) file?

[Sven N. Thommesen]

Jan,

the documentation for this used to be in the "Random Appendix" to the 
reference guide, but the powers that be have now transferred some of what I 
wrote to the "Beta Users Guide" which you can find at the Swarm.Org web 
site. Check out section C.2.1.3. I have appended to this message the code 
in the random test suite that exercises the save-state/set-state machinery. 
If this doesn't run correctly at your site, I'll be happy to send you the 
whole test suite so we can figure things out.

I notice that your code differs from mine in that you have "unsigned 
*rngState" while I have and id, and my pointer is a (void *) rather than 
(unsigned *). Don't know if that's the source of your problem.

Perhaps Marcus has a point that I ought to add code to save and retrieve 
the random objects using lisp and/or hdf5, but from my own perspective it 
is a *feature*, not a bug, that the internals of the state are kept hidden ;-)

Marcus: perhaps a pointer from the (shortened) reference guide to the 
material now in the User Guide would be useful?

Cheers,
Sven Thommesen

At 10:20 AM 6/13/2000 +0100, you wrote:
> Dear all,
>
> I'm trying to regularly save the state of the default MT19937 rng into a
> file, to be able to restart a run where it broke off due to power cut etc.
>
> Now I got thus far:
>
>   unsigned rngStateSize;
>   unsigned *rngState;
>
>   rngStateSize = [randSource getStateSize]; // gives 5020
>   rngState = (unsigned *) [globalZone alloc: [randSource getStateSize]];
>   [randSource putStateInto: rngState];
>
>   // how to save the state?
>
>   // how to read that in again?
>
>   [randSource setStateFrom: rngState];
>   [globalZone free: rngState];
>
> (randSource is a pointer to the MT19937 generator)
>
> Has someone got an example of how to do this? I couldn't find anything in
> the archive?
>
> Thanks, Jan.
>
> Jan Kreft                               Phone  +44 (0)29 20875278
> Cardiff School of Biosciences           Fax    +44 (0)29 20874305
> Cardiff University                      E-mail address@hidden
> PO Box 915, Cardiff CF10 3TL, UK
>
>
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