You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
98 lines
2.4 KiB
98 lines
2.4 KiB
// A Javascript implementaion of the "xorshift7" algorithm by
|
|
// François Panneton and Pierre L'ecuyer:
|
|
// "On the Xorgshift Random Number Generators"
|
|
// http://saluc.engr.uconn.edu/refs/crypto/rng/panneton05onthexorshift.pdf
|
|
|
|
(function(global, module, define) {
|
|
|
|
function XorGen(seed) {
|
|
var me = this;
|
|
|
|
// Set up generator function.
|
|
me.next = function() {
|
|
// Update xor generator.
|
|
var X = me.x, i = me.i, t, v, w;
|
|
t = X[i]; t ^= (t >>> 7); v = t ^ (t << 24);
|
|
t = X[(i + 1) & 7]; v ^= t ^ (t >>> 10);
|
|
t = X[(i + 3) & 7]; v ^= t ^ (t >>> 3);
|
|
t = X[(i + 4) & 7]; v ^= t ^ (t << 7);
|
|
t = X[(i + 7) & 7]; t = t ^ (t << 13); v ^= t ^ (t << 9);
|
|
X[i] = v;
|
|
me.i = (i + 1) & 7;
|
|
return v;
|
|
};
|
|
|
|
function init(me, seed) {
|
|
var j, w, X = [];
|
|
|
|
if (seed === (seed | 0)) {
|
|
// Seed state array using a 32-bit integer.
|
|
w = X[0] = seed;
|
|
} else {
|
|
// Seed state using a string.
|
|
seed = '' + seed;
|
|
for (j = 0; j < seed.length; ++j) {
|
|
X[j & 7] = (X[j & 7] << 15) ^
|
|
(seed.charCodeAt(j) + X[(j + 1) & 7] << 13);
|
|
}
|
|
}
|
|
// Enforce an array length of 8, not all zeroes.
|
|
while (X.length < 8) X.push(0);
|
|
for (j = 0; j < 8 && X[j] === 0; ++j);
|
|
if (j == 8) w = X[7] = -1; else w = X[j];
|
|
|
|
me.x = X;
|
|
me.i = 0;
|
|
|
|
// Discard an initial 256 values.
|
|
for (j = 256; j > 0; --j) {
|
|
me.next();
|
|
}
|
|
}
|
|
|
|
init(me, seed);
|
|
}
|
|
|
|
function copy(f, t) {
|
|
t.x = f.x.slice();
|
|
t.i = f.i;
|
|
return t;
|
|
}
|
|
|
|
function impl(seed, opts) {
|
|
if (seed == null) seed = +(new Date);
|
|
var xg = new XorGen(seed),
|
|
state = opts && opts.state,
|
|
prng = function() { return (xg.next() >>> 0) / 0x100000000; };
|
|
prng.double = function() {
|
|
do {
|
|
var top = xg.next() >>> 11,
|
|
bot = (xg.next() >>> 0) / 0x100000000,
|
|
result = (top + bot) / (1 << 21);
|
|
} while (result === 0);
|
|
return result;
|
|
};
|
|
prng.int32 = xg.next;
|
|
prng.quick = prng;
|
|
if (state) {
|
|
if (state.x) copy(state, xg);
|
|
prng.state = function() { return copy(xg, {}); }
|
|
}
|
|
return prng;
|
|
}
|
|
|
|
if (module && module.exports) {
|
|
module.exports = impl;
|
|
} else if (define && define.amd) {
|
|
define(function() { return impl; });
|
|
} else {
|
|
this.xorshift7 = impl;
|
|
}
|
|
|
|
})(
|
|
this,
|
|
(typeof module) == 'object' && module, // present in node.js
|
|
(typeof define) == 'function' && define // present with an AMD loader
|
|
);
|
|
|