Function PGARandom01

Function Documentation

double PGARandom01(PGAContext *ctx, int newseed)

Generate a uniform random number on the interval [0,1).

Description

If the second argument is 0 it returns the next random number in the sequence. Otherwise, the second argument is used as a new seed for the population.

This is a C language implementation of the universal random number generator proposed by George Marsaglia, Arif Zaman, and Wai Wan Tsang [MZT90] and translated from F. James’ version [Jam90].

This algorithm is a combination of a lagged Fibonacci and arithmetic sequence (F. James) generator with period of \(2^{144}\). It provides 32-bit floating point numbers in the range from zero to one. It is claimed to be portable and provides bit-identical results on all machines with at least 24-bit mantissas.

PGARandom01() should be initialized with a 32-bit integer seed such that \(0 \le seed \le 900,000,000\). Each of these 900,000,000 values gives rise to an independent sequence of \(\approx 10^{30}\).

Warning on use of static storage class on thread shared memory machines.

Example

To get the next random number use

PGAContext *ctx;
double r;

...
r = PGARandom01 (ctx, 0);

Parameters

  • ctx – context variable

  • newseed – either 0 to get the next random number, or nonzero to reseed

Returns

A random number on the interval [0,1)