메르센 트위스터 난수 생성 알고리즘

mersenne_twister.js

const N = 624;
const M = 397;
const F = 1812433253;

const UPPER_MASK = (2 ** 32) / 2; // 0x80000000
const LOWER_MASK = UPPER_MASK - 1; // 0x7fffffff
const MATRIX_A = 0x9908b0df;

class MersenneTwister {
  constructor () {
    const initSeed = new Date().getTime();
    this.mt = new Array(N);
    this.index = N + 1;

    this.seedMt(initSeed);
  }

  seedMt (seed) {
    let s;

    this.mt[0] = seed >>> 0;

    for (this.index = 1; this.index < N; this.index++) {
      this.mt[this.index] = F * (this.mt[this.index - 1] ^ (this.mt[this.index - 1]) >>> 30) + this.index;
      this.mt[this.index] &= 0xffffffff;
    }
  }

  int () {
    let y;
    const mag01 = new Array(0, MATRIX_A);
    if (this.index >= N) {
      let kk;

      if (this.index === N + 1) {
        this.seedMt(5489);
      }

      for (kk = 0; kk < N - M; kk++) {
        y = (this.mt[kk] & UPPER_MASK) | (this.mt[kk + 1] & LOWER_MASK);
        this.mt[kk] = this.mt[kk + M] ^ (y >>> 1) ^ mag01[y & 1];
      }

      for (; kk < N - 1; kk++) {
        y = (this.mt[kk] & UPPER_MASK) | (this.mt[kk + 1] & LOWER_MASK);
        this.mt[kk] = this.mt[kk + (M - N)] ^ (y >>> 1) ^ mag01[y & 1];
      }

      y = (this.mt[N - 1] & UPPER_MASK) | (this.mt[0] & LOWER_MASK);
      this.mt[N - 1] = this.mt[M - 1] ^ (y >>> 1) ^ mag01[y & 1];
      this.index = 0;
    }

    y = this.mt[this.index++];

    y ^= (y >>> 11);
    y ^= (y << 7) & 0x9d2c5680;
    y ^= (y << 15) & 0xefc60000;
    y ^= (y >>> 18);

    return y >>> 0;
  };
}

const m = new MersenneTwister();
console.log(m.int());