Special simple random number generator

Question

How to create a function, which on every call generates a random integer number? This number must be most random as possible (according to uniform distribution). It is only

Answer 1

Here's a function with uniform distribution over the entire range of int:

int rand()
{
  static int random = 0;
  return random++;
}

Answer 2

I use this

SUBROUTINE GNA(iiseed)
    USE Variaveis
    parameter (ia=843314861,ib=453816693,m=1073741824, r231=1./2147483648.)
    INTEGER :: iiseed

    iiseed = ib + ia*iiseed
    if (iiseed.lt.0) iiseed = (iiseed+m) + m
    RndNum = iiseed*r231

END SUBROUTINE GNA

A big gain of randomness can be achieved without spending more computational time creating a random number generator for each call the random number generator made in the program.

This is a very good trick!

Answer 3

You might have a look at this. It's far from beeing a "perfect" random number generator, but it does fulfil your requirements as far as i can see.

Here you can find some additional information about random number generation.

Answer 4

Boost has a very nice random number library, and the source code is available, so you could try looking there and using what you need (i.e. cut and paste).

Answer 5

public long randomLong() {
  x ^= (x << 21);
  x ^= (x >>> 35);
  x ^= (x << 4);
  return x;
}

Seed cannot be 0. Source: http://www.javamex.com/tutorials/random_numbers/xorshift.shtml#.VlcaYzKwEV8

Additional info in wiki: https://en.wikipedia.org/wiki/Xorshift

Answer 6

If I write man rand, I can read a possible example, given in POSIX.1-2001, for implementing rand() and srand(). See e.g. here. If you need something more sophisticated, take a look at GNU Scientific Library; you can of course download the code and see the implementation(s).