Kyle Schmitt wrote:
> This is going to sound like a smartass answer, but real random numbers
> are really random, psudo random numbers are random-ish.
>
> Most "random" number generators are actually periodic, even if they
> have large periods.  I could be wrong, but having to specify a seed is
> a clue it's psudo random.  Seeding a "random" number generator is a
> way to increase it's randomness somewhat.  With the good old C rand
> function, try seeding it with 10 (using srand) and write it out to a
> file.  Run it as many times as you want, and you'll end up with the
> SAME file.
>
> Some modern computers have real entropy sources built in, and for
> those that don't, it's possible to collect entropy from various places
> (you'll have to do some googling about openbsd since they go nuts with
> this).  You can use an entropy source as a _real_ random number
> generator, or to seed a psudo random number generator to make it a
> little less periodic.
>
> If you want to be lazy there used to be a series of books called
> numerical recipies in %w{c pascal youre-favorite-language}.  One thing
> they showed was a good random number generator, and apparently they
> went into some depth on the subject.
>
> Places where random vs psudo random are important:
> If you are running models that use random numbers (a friend of mine
> was going really neurotic once trying to make sure his supernovas
> modeller was really really random)
> Cryptography
> umm... uhh... yea I can't think of more right now.
>
http://realrand.rubyforge.org/