Class LCG

Summary

A linear congruential random number generator.

Description

Uses D.H. Lehmer's Linear Congruential Method (1949) for generating random numbers. Supports both Multiplicative Congruential Method (increment==0) and Mixed Congruential Method (increment!=0) It is perhaps the simplest and fastest method to generate pseudo-random numbers on a computer. Per default uses the values for Minimal Standard LCG. http://en.wikipedia.org/wiki/Linear_congruential_generatorhttp://www.math.rutgers.edu/~greenfie/currentcourses/sem090/pdfstuff/jp.pdf

Pros:

• Easy to implement.

• Fast.

Cons:

• NOT safe for cryptography because of the easily calculatable sequential correlation between successive calls. A case study: http://www.cigital.com/papers/download/developer_gambling.php

• Tends to have less random low-order bits (compared to the high-order bits) Thus, NEVER do something like this:

  u32 numBetween1And10 = 1 + LCGRand.Int() % 10;

  Instead, take into account EVERY bit of the generated number, like this:

  u32 numBetween1And10 = 1 + (int)(10.0 * (double)LCGRand.Int() /(LCGRand.Max()+1.0)); or simply

  u32 numBetween1And10 = LCGRand.Float(1.f, 10.f);