[javascript]Mersenne Twister Pseudo Random Number Generator

mt.js

// Mersenne Twister Random Generator                                            
// see: http://en.wikipedia.org/wiki/Mersenne_twister                           
var MT = function MT(seed) {
    seed = typeof seed === "number" ? seed: Date.now();
    var self = Object.create(MT.prototype, {
        mt: {value: new Array(MT.N)},
        index: {value: 0, writable: true},
    });
    // initialize from a seed with LCG PRNG                                     
    var pre = self.mt[0] = seed & MT.MASK_F;
    for (var i = 1; i < MT.N; i++) {
        var n = (MT.I * (pre ^ (pre >> MT.Q)) + i) & MT.MASK_F;
        pre = self.mt[i] = n;
    }
    return self;
};

// spec of this MT                                                              
MT.P = 199937 // 2^P - 1 cycle                                                  
MT.W = 32;    // word size                                                      
// coefficeints for the MT199937                                                
MT.R = 31;
MT.N = 624;
MT.M = 397;
MT.A = 0x9908b0df;
MT.B = 0x9d2c5680;
MT.C = 0xefc60000;
MT.S = 7;
MT.T = 15;
MT.U = 11;
MT.L = 18;
MT.MASK_F = 0xffffffff; // Math.pow(2, MT.W) - 1                                
MT.MASK_L = 0x7fffffff; // Math.pow(2, MT.R) - 1                                
MT.MASK_U = 0x80000000; // MT.MASK_F - MT.MASK_L                                
// LCG params for initialize                                                    
MT.I = 0x6c078965; // well-known better multiplier 1812433253 for LCG            
MT.Q = 30; // MT.W - 2                                                          

// next random integer                                                          
MT.prototype.next = function () {
    var mt = this.mt;
    if (this.index === 0) {
        // generate numbers                                                     
        for (var k = 0; k < MT.N; k++) {
            var n = (mt[k] & MT.MASK_U) | (mt[(k + 1) % MT.N] & MT.MASK_L);
            mt[k] = mt[(k + MT.M) % MT.N] ^ (n >> 1) ^ (n % 2 ? MT.A : 0);
        }
    }
    // extract number                                                           
    var r = mt[this.index];
    r ^= (r >> MT.U);
    r ^= (r << MT.S) & MT.B;
    r ^= (r << MT.T) & MT.C;
    r ^= (r >> MT.L);
    this.index = (this.index + 1) % MT.N;
    return r;
};

// example                                                                      
var mt = MT(0);
for (var i = 0; i < 10; i++) {
    console.log(mt.next());
}