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/