Better randomization, especially for GUID generation

[jeffrose]

Better randomization, especially for GUID generation

[millermedeiros]

I agree that Math.random() isn't good enough and that a seeded random is extremely useful. I will take a look on the document and implementations and check out if we can use it or not.

[bebraw]

Do you think Mersenne Twister would do the trick? I used that once to get repeatable random numbers (you can set the seed). Perhaps it will work for your purposes too.

[jeffrose]

The page I referenced mentions Mersenne Twister a couple times and precludes using it since it fails Crush randomness tests.

[millermedeiros]

I was thinking about it and I fell that providing a single algorithm is not going to be a good idea and is also out of the scope of this project (besides the fact that it is really hard to test PRNG properly).

I think we should add a way to swap the PRNG used by each method so you could curry each method individually and use different seeds for each one:

var mt = new MersenneTwister('magic beans seed');
var mtRandom = function(){ return mt.random() };
var randInt_1 = randInt.create( mtRandom );
var randInt_2 = randInt.create( KISS07('sunflower seed') );

And also add a way to replace it on an existing instance:

// default value = Math.random;
randInt.random = Kybos('foobar');

And maybe create a new module random/random that is used by all the methods inside the random package (avoid calling Math.random() directly), so replacing it would be enough to propagate the change to all random methods:

define(function(){
   function random(){
     return random.random();
   }
   // expose a `random` property so user can swap the behavior dynamically
   random.random = Math.random;
   return random;
});

Could also use the RequireJS map config to replace the amd-utils/random/random module, but I like the idea of exposing the random property since on node.js there is no such a thing as a map config.

PS: that way we also avoid any licensing issues.

[jeffrose]

I definitely like the flexibility that having a separate module, random/random, provides. I assume the default implementation will still be Math.random(). There should probably be some comment about the unreliability of Math.random() especially for UUID generation.

Having said that random/random looks a little funny. Maybe random/gen? random/generator? random/ng? random/prng?

[millermedeiros]

I added the random/random, since I think it will only be used internally (easier to call Math.random directly) I think the name is good enough.

I didn't implemented the randInt.create(), choice.create(), etc.. or added a new property random to each method since I think it will increase complexity a lot and the global replacement should be enough for most use cases (overriding amd-utils/random/random behavior).

I improved the documentation a lot adding info on the top about Math.random usage and also improved the guid documentation to mention safety problems. random/random gets into a lot of details so it should be clear to everyone: http://millermedeiros.github.com/amd-utils/random.html

Thanks for all the feedback and for helping me to improve amd-utils. Feel free to reopen the issue.

[millermedeiros]

for future reference this article is great: http://www.empiricalzeal.com/2012/12/21/what-does-randomness-look-like/

[jeffrose]

Thanks! I'll check it out.