feat:node-modules

node_modules/seedrandom/lib/xor4096.js

@@ -0,0 +1,146 @@
+// A Javascript implementaion of Richard Brent's Xorgens xor4096 algorithm.
+//
+// This fast non-cryptographic random number generator is designed for
+// use in Monte-Carlo algorithms. It combines a long-period xorshift
+// generator with a Weyl generator, and it passes all common batteries
+// of stasticial tests for randomness while consuming only a few nanoseconds
+// for each prng generated.  For background on the generator, see Brent's
+// paper: "Some long-period random number generators using shifts and xors."
+// http://arxiv.org/pdf/1004.3115v1.pdf
+//
+// Usage:
+//
+// var xor4096 = require('xor4096');
+// random = xor4096(1);                        // Seed with int32 or string.
+// assert.equal(random(), 0.1520436450538547); // (0, 1) range, 53 bits.
+// assert.equal(random.int32(), 1806534897);   // signed int32, 32 bits.
+//
+// For nonzero numeric keys, this impelementation provides a sequence
+// identical to that by Brent's xorgens 3 implementaion in C.  This
+// implementation also provides for initalizing the generator with
+// string seeds, or for saving and restoring the state of the generator.
+//
+// On Chrome, this prng benchmarks about 2.1 times slower than
+// Javascript's built-in Math.random().
+
+(function(global, module, define) {
+
+function XorGen(seed) {
+  var me = this;
+
+  // Set up generator function.
+  me.next = function() {
+    var w = me.w,
+        X = me.X, i = me.i, t, v;
+    // Update Weyl generator.
+    me.w = w = (w + 0x61c88647) | 0;
+    // Update xor generator.
+    v = X[(i + 34) & 127];
+    t = X[i = ((i + 1) & 127)];
+    v ^= v << 13;
+    t ^= t << 17;
+    v ^= v >>> 15;
+    t ^= t >>> 12;
+    // Update Xor generator array state.
+    v = X[i] = v ^ t;
+    me.i = i;
+    // Result is the combination.
+    return (v + (w ^ (w >>> 16))) | 0;
+  };
+
+  function init(me, seed) {
+    var t, v, i, j, w, X = [], limit = 128;
+    if (seed === (seed | 0)) {
+      // Numeric seeds initialize v, which is used to generates X.
+      v = seed;
+      seed = null;
+    } else {
+      // String seeds are mixed into v and X one character at a time.
+      seed = seed + '\0';
+      v = 0;
+      limit = Math.max(limit, seed.length);
+    }
+    // Initialize circular array and weyl value.
+    for (i = 0, j = -32; j < limit; ++j) {
+      // Put the unicode characters into the array, and shuffle them.
+      if (seed) v ^= seed.charCodeAt((j + 32) % seed.length);
+      // After 32 shuffles, take v as the starting w value.
+      if (j === 0) w = v;
+      v ^= v << 10;
+      v ^= v >>> 15;
+      v ^= v << 4;
+      v ^= v >>> 13;
+      if (j >= 0) {
+        w = (w + 0x61c88647) | 0;     // Weyl.
+        t = (X[j & 127] ^= (v + w));  // Combine xor and weyl to init array.
+        i = (0 == t) ? i + 1 : 0;     // Count zeroes.
+      }
+    }
+    // We have detected all zeroes; make the key nonzero.
+    if (i >= 128) {
+      X[(seed && seed.length || 0) & 127] = -1;
+    }
+    // Run the generator 512 times to further mix the state before using it.
+    // Factoring this as a function slows the main generator, so it is just
+    // unrolled here.  The weyl generator is not advanced while warming up.
+    i = 127;
+    for (j = 4 * 128; j > 0; --j) {
+      v = X[(i + 34) & 127];
+      t = X[i = ((i + 1) & 127)];
+      v ^= v << 13;
+      t ^= t << 17;
+      v ^= v >>> 15;
+      t ^= t >>> 12;
+      X[i] = v ^ t;
+    }
+    // Storing state as object members is faster than using closure variables.
+    me.w = w;
+    me.X = X;
+    me.i = i;
+  }
+
+  init(me, seed);
+}
+
+function copy(f, t) {
+  t.i = f.i;
+  t.w = f.w;
+  t.X = f.X.slice();
+  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.xor4096 = impl;
+}
+
+})(
+  this,                                     // window object or global
+  (typeof module) == 'object' && module,    // present in node.js
+  (typeof define) == 'function' && define   // present with an AMD loader
+);