# Description of the routines contained in: rand.c

Sometimes it is useful to use sophisticated routines to produce random numbers. The file rand.c contains a couple of quite good random number generators. If you want to use one of them, first call the routine rnd_init(seed) with some integer number seed to initialize the generators. You have the choice between the following generators:

- rnd_long(): It returns an unsigned long random number generated by the following rule:
  xn+1=xn-9689 XOR xn-157 XOR xn-314 XOR xn-471
  It has a period of 2^9689 and the numbers are uncorrelated up to 4 point correlations.
- rnd_1279(): It returns an unsigned long random number generated by the following rule:
  xn+1=xn-1279+ xn-216+xn-299+ xn-598
  It has a period of 2^1279 and the numbers are uncorrelated up to 4 point correlations.
- rnd69069(): It returns an unsigned long random number generated by the following rule:
  xn+1=xn*factor+1
  where factor=69069 on 32 Bit machines and factor=13^13 on 64 Bit machines. This one is fast and especially on 64 Bit machines good for almost all purposes.
- gaussian(): Returns random numbers which are distributed gaussian with a variance of variance centered around zero. Interally it uses the routine rnd_1279().

View the C-sources.

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