octo-deno/lib/random/mersennetwister.js
2017-04-23 01:49:49 +03:00

86 lines
2 KiB
JavaScript

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* JavaScript version of Mersenne Twister
*
* @author Yasuharu Okada
*
*/
function MersenneTwister() {
const N = 624;
const M = 397;
const UPPER_MASK = 0x80000000;
const LOWER_MASK = 0x7fffffff;
const MAG01 = new Int32Array([0, 0x9908b0df]);
let mt = new Int32Array(N);
/* the array for the state vector */
let mti = 625;
this.seed = function (s) {
mt[0] = s | 0;
for (mti = 1; mti < N; mti++) {
mt[mti] = Math.imul(1812433253, mt[mti - 1] ^ (mt[mti - 1] >>> 30)) + mti;
}
};
this.export_state = function () {
return [mt, mti];
};
this.import_state = function (s) {
mt = s[0];
mti = s[1];
};
this.export_mta = function () {
return mt;
};
this.import_mta = function (_mta) {
mt = _mta;
};
this.export_mti = function () {
return mti;
};
this.import_mti = function (_mti) {
mti = _mti;
};
this.int32 = function () {
let y, kk;
if (mti >= N) { /* generate N words at one time */
for (kk = 0; kk < N - M; kk++) {
y = ((mt[kk] & UPPER_MASK) | (mt[kk + 1] & LOWER_MASK));
mt[kk] = (mt[kk + M] ^ (y >>> 1) ^ MAG01[y & 0x1]);
}
for (; kk < N - 1; kk++) {
y = ((mt[kk] & UPPER_MASK) | (mt[kk + 1] & LOWER_MASK));
mt[kk] = (mt[kk + (M - N)] ^ (y >>> 1) ^ MAG01[y & 0x1]);
}
y = ((mt[N - 1] & UPPER_MASK) | (mt[0] & LOWER_MASK));
mt[N - 1] = (mt[M - 1] ^ (y >>> 1) ^ MAG01[y & 0x1]);
mti = 0;
}
y = mt[mti++];
/* Tempering */
y = y ^ (y >>> 11);
y = y ^ ((y << 7) & 0x9d2c5680);
y = y ^ ((y << 15) & 0xefc60000);
y = y ^ (y >>> 18);
return y >>> 0;
};
this.real2 = function () {
return ((this.int32() >>> 5) * 67108864.0 + (this.int32() >>> 6)) / 9007199254740992.0;
};
}