[Newbies] Randomness

[Bert Freudenberg]

The new behavior is that you get a different stream of random numbers each time you start the image. Or at least it's really really unlikely you get the same sequence again. 

- Bert -

On 07.04.2011, at 02:54, michael rice wrote:

> So it was a problem? The old behavior was: if I saved a project and quit the image without saving it, the next time I bought up the image and loaded the project I would get the same stream of random numbers. What is the new behavior?
> 
> Michael
> 
> --- On Wed, 4/6/11, David T. Lewis <lewis at mail.msen.com> wrote:
> 
> From: David T. Lewis <lewis at mail.msen.com>
> Subject: Re: [Newbies] Randomness
> To: "A friendly place to get answers to even the most basic questions about Squeak." <beginners at lists.squeakfoundation.org>
> Date: Wednesday, April 6, 2011, 8:35 PM
> 
> I made the update in Squeak trunk similar to the Etoys image, but used
> the existing seed generator in Random>>initialize on the theory that if
> the generator is good enough for a new Random, it should be good enough
> for an existing one too ;)
> 
> Michael, thanks for spotting the problem.
> 
> Dave
> 
> On Tue, Apr 05, 2011 at 01:16:31PM +0200, Bert Freudenberg wrote:
> > 
> > On 05.04.2011, at 02:32, Levente Uzonyi wrote:
> > 
> > > On Mon, 4 Apr 2011, michael rice wrote:
> > > 
> > >> I forgot to mention, I'm using the random number tile and scripting. Does that make it more difficult?
> > > 
> > > Not really, RandomNumberTile uses the global random number generator of Collection. I don't know how/why is it serialized/restored
> > 
> > It is not stored in the project. But in trunk, the seed does not get re-initialized when starting up. In the Etoys image, Collection class has a startUp method
> > 
> > startUp
> >     RandomForPicking seed: Time totalSeconds hash asFloat.
> > 
> > IMHO we should adopt something like this for trunk (maybe with your "more" random approach below). 
> > 
> > - Bert -
> > 
> > > but here's a method which should help:
> > > 
> > > RandomNumberTile >> #comeFullyUpOnReload: smartRefStream
> > > 
> > >     | seed |
> > >     [
> > >         seed := (Time millisecondClockValue bitAnd: 16r3FFFFFFF) bitXor: self hash.
> > >         seed := seed bitXor: (Time totalSeconds bitAnd: 16r3FFFFFFF).
> > >         seed := seed bitXor: 16r3FFFFFFF atRandom.
> > >         seed = 0 ] whileTrue. "Try again if ever get a seed = 0"
> > >     Collection mutexForPicking critical: [
> > >         Collection randomForPicking seed: seed ].
> > >     ^super comeFullyUpOnReload: smartRefStream
> > > 
> > > It's drawback is that it will reseed the rng for every RandomNumberTile. The best solution would be if Etoys would use a custom Random instance or a subclass where this is done by default.
> > > 
> > > 
> > > Levente
> > > 
> > >> 
> > >> Michael
> > >> 
> > >> --- On Mon, 4/4/11, Levente Uzonyi <leves at elte.hu> wrote:
> > >> 
> > >> From: Levente Uzonyi <leves at elte.hu>
> > >> Subject: Re: [Newbies] Randomness
> > >> To: "A friendly place to get answers to even the most basic questions about Squeak." <beginners at lists.squeakfoundation.org>
> > >> Date: Monday, April 4, 2011, 8:08 PM
> > >> 
> > >> On Mon, 4 Apr 2011, michael rice wrote:
> > >> 
> > >>> I just noticed that when I load a morphic project I get the same stream of random numbers each time. Is there a simple way to install a new different random seed each time the project is loaded?
> > >> 
> > >> If you serialize the Random object, then it will have the same state when it's restored. I guess you should create a subclass of Random, which implements #comeFullyUpOnReload:. That method can reinitialize the seed of the random number generator. You may want to check UUIDGenerator >> #makeSeed if you don't know how to get a good seed for your rng.
> > >> 
> > >> 
> > >> Levente
> > 




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