octo-deno/lib/random/mersennetwister.js
2018-03-19 05:54:40 +01:00

89 lines
2.3 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
*
*/
class MersenneTwister {
constructor () {
this.N = 624
this.M = 397
this.UPPER_MASK = 0x80000000
this.LOWER_MASK = 0x7fffffff
this.MAG01 = new Int32Array([0, 0x9908b0df])
this.mt = new Int32Array(this.N)
this.mti = 625 // The array for the state vector.
}
seed (s) {
this.mt[0] = s | 0
for (this.mti = 1; this.mti < this.N; this.mti++) {
this.mt[this.mti] = Math.imul(1812433253, this.mt[this.mti - 1] ^ (this.mt[this.mti - 1] >>> 30)) + this.mti
}
}
export_state () { // eslint-disable-line camelcase
return [this.mt, this.mti]
}
import_state (s) { // eslint-disable-line camelcase
this.mt = s[0]
this.mti = s[1]
}
export_mta () { // eslint-disable-line camelcase
return this.mt
}
import_mta (_mta) { // eslint-disable-line camelcase
this.mt = _mta
}
export_mti () { // eslint-disable-line camelcase
return this.mti
}
import_mti (_mti) { // eslint-disable-line camelcase
this.mti = _mti
}
int32 () {
let y, kk
if (this.mti >= this.N) { /* generate N words at one time */
for (kk = 0; kk < this.N - this.M; kk++) {
y = ((this.mt[kk] & this.UPPER_MASK) | (this.mt[kk + 1] & this.LOWER_MASK))
this.mt[kk] = (this.mt[kk + this.M] ^ (y >>> 1) ^ this.MAG01[y & 0x1])
}
for (; kk < this.N - 1; kk++) {
y = ((this.mt[kk] & this.UPPER_MASK) | (this.mt[kk + 1] & this.LOWER_MASK))
this.mt[kk] = (this.mt[kk + (this.M - this.N)] ^ (y >>> 1) ^ this.MAG01[y & 0x1])
}
y = ((this.mt[this.N - 1] & this.UPPER_MASK) | (this.mt[0] & this.LOWER_MASK))
this.mt[this.N - 1] = (this.mt[this.M - 1] ^ (y >>> 1) ^ this.MAG01[y & 0x1])
this.mti = 0
}
y = this.mt[this.mti++]
/* Tempering */
y = y ^ (y >>> 11)
y = y ^ ((y << 7) & 0x9d2c5680)
y = y ^ ((y << 15) & 0xefc60000)
y = y ^ (y >>> 18)
return y >>> 0
}
real2 () {
return ((this.int32() >>> 5) * 67108864.0 + (this.int32() >>> 6)) / 9007199254740992.0
}
}
module.exports = MersenneTwister