[Newbies] Randomness

[Bert Freudenberg]

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