====== Mersenne Twister (PRNG) ======
^versions^0095+^
|contributors|[[user:watz]]|
|started on|2006-05-16 10:16|

I've been using a replacement for Java's built-in Random class for many years now. java.util.Random is less than mathematically perfect, and is useless when one wants to generate a series of pseudo-random numbers that will be consistent on different computers and VMs.

Looking at Paul Houle's [[http://www.honeylocust.com/RngPack/|RngPack]] library, I found an implementation of the Mersenne Twister generator. The Mersenne Twister is considered research-grade, has a very long (2^19937-1) period and produces consistent numbers on different computers. It even computes faster than Math.random(). See [[http://en.wikipedia.org/wiki/Mersenne_twister|Wikipedia: Mersenne Twister]] for a breakdown of other bonuses, such as "a very high order of dimensional equidistribution".

I figured it might be useful to other people as well, so I have packaged it as a JAR file for use as a library with Processing. It's very easy to use, as you can see in the code example below.

===== Source code =====

<code processing>
/**
mersennetwister taken from http://processinghacks.com/hacks:mersennetwister
@author Marius Watz
*/

import mw.randomMT;
 
randomMT rnd=new randomMT(); // Use default seed
rnd=new randomMT(System.currentTimeMillis()); // Use system clock to set seed
 
float val=rnd.random(100);
val=rnd.random(20,50);
println("val "+val);
 
int intval=rnd.randomInt(30);
println("intval "+intval);
 
if(rnd.probGt(60)) println("Probability greater than 60.");
else println("Probability lesser than 60.");
 
println("randomBool returned "+rnd.randomBool());
</code>

===== Downloads =====

[[http://workshop.evolutionzone.com/code/randomMT/mw_randomMT.zip|mw_randomMT.zip]]

===== Related Links =====

[[http://www.honeylocust.com/RngPack/|Paul Houle's RngPack library]], which includes other number generators.\\
[[http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html|Mersenne Twister homepage]]\\
[[http://en.wikipedia.org/wiki/Mersenne_twister|Wikipedia: Mersenne Twister]]\\
[[http://en.wikipedia.org/wiki/Pseudorandom_number_generator|Wikipedia: Pseudorandom number generator]]