[Newbies] Randomness

[Levente Uzonyi]

On Tue, 5 Apr 2011, 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

So it doesn't give the same random numbers after project loading, but 
after image startup in Squeak?

>
> startUp
> 	RandomForPicking seed: Time totalSeconds hash asFloat.
>
> IMHO we should adopt something like this for trunk (maybe with your "more" random approach below).

It can be even better, I just copied (and slightly modified) the code from 
UUIDGenerator. Maybe it's the best to move the reseeding code to Random.


Levente

>
> - 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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