Wichmann–Hill
# Wichmann–Hill

Wichmann–Hill is a pseudorandom number generator proposed in 1982 by Brian Wichmann and David Hill. It consists of three linear congruential generators with different prime moduli, each of which is used to produce a uniformly distributed number between 0 and 1. These are summed, modulo 1, to produce the result.

Summing three generators produces a pseudorandom sequence with cycle exceeding $6.95×10^{12}.$ Specifically, the moduli are 30269, 30307 and 30323, producing periods of 30268, 30306 and 30322. The overall period is the least common multiple of these: 30268×30306×30322/4 = 6953607871644. This has been confirmed by a brute-force search.

## Implementation

The following pseudocode is for implementation on machines capable of integer arithmetic up to 5,212,632:

For machines limited to 16-bit signed integers, the following equivalent code only uses numbers up to 30,323:

The seed values s1, s2 and s3 must be initialized to non-zero values.

