Steve Park
This is an ANSI C library for multi-stream random number generation. The use of this library is recommended as a replacement for the ANSI C rand() and srand() functions, particularly in simulation applications where the statistical 'goodness' of the random number generator is important. The library supplies 256 streams of random numbers; use SelectStream(s) to switch between streams indexed s = 0,1,...,255.
The generator used in this library is a so-called 'Lehmer random number generator' which returns a pseudo-random number uniformly distributed 0.0 and 1.0. The period is (m - 1) where m = 2,147,483,647 and the smallest and largest possible values are (1 / m) and 1 - (1 / m) respectively. For more details see:
For more information about the libraries rngs and rvgs, or for information about the status of the related Prentice-Hall textbook Discrete-Event Simulation: A First Course by Steve Park and Larry Leemis, please contact leemis@math.wm.edu.
The bracketed links below are to ANSI C files. If you wish to save the files below rather than view them, click on the link with the SHIFT key depressed. With a Netscape browser, this will bring up a "Save As" dialog box.
| [rng.tgz] |
| [rngs.h] | [rngs.c] |
| Generator | Range (x) | Mean | Variance |
| Bernoulli(p) | x = 0,1 | p | p*(1-p) |
| Binomial(n, p) | x = 0,...,n | n*p | n*p*(1-p) |
| Equilikely(a,b) | x = a,...,b | (a+b)/2 | ((b-a+1)*(b-a+1)-1)/12 |
| Geometric(p) | x = 0,... | p/(1-p) | p/((1-p)*(1-p)) |
| Pascal(n, p) | x = 0,... | n*p/(1-p) | n*p/((1-p)*(1-p)) |
| Poisson(m) | x = 0,... | m | m |
| Generator | Range (x) | Mean | Variance |
| Uniform(a, b) | a < x < b | (a + b)/2 | (b - a)*(b - a)/12 |
| Exponential(m) | x > 0 | m | m*m |
| Erlang(n, b) | x > 0 | n*b | n*b*b |
| Normal(m, s) | all x | m | s*s |
| Lognormal(a, b) | x > 0 | exp(a + 0.5*b*b) | (exp(b*b) - 1) * exp(2*a + b*b) |
| Chisquare(n) | x > 0 | n | 2*n |
| Student(n) | all x | 0 (n > 1) | n/(n - 2) (n > 2) |
| [rvgs.h] | [rvgs.c] |