Code coverage report for seedrandom/lib/xor4096.js

# All files / seedrandom/lib xor4096.js

92.68% Statements 76/82
65.71% Branches 23/35
90% Functions 9/10
94.52% Lines 69/73

Press n or j to go to the next uncovered block, b, p or k for the previous block.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    86
    87
    88
    89
    90
    91
    92
    93
    94
    95
    96
    97
    98
    99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147

    1x

    3x

    3x
    4105129x
    4105129x

    4105129x

    4105129x
    4105129x
    4105129x
    4105129x
    4105129x
    4105129x

    4105129x
    4105129x

    4105129x

    3x
    3x

    2x
    2x

    1x
    1x
    1x

    3x

    480x

    480x
    480x
    480x
    480x
    480x
    480x
    384x
    384x
    384x

    3x

    3x
    3x
    1536x
    1536x
    1536x
    1536x
    1536x
    1536x
    1536x

    3x
    3x
    3x

    3x

    2x
    2x
    2x
    2x

    3x
    3x
    3x
    4102054x
    3x
    1025x
    1025x
    1025x
    1025x

    1025x

    3x
    3x
    3x
    2x
    2x

    3x

    1x
    1x

     // 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.
        Iif (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) {
      Iif (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;
    }

    Eif (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
    );