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// Copyright 2014 Thom Chiovoloni, released under the MIT license. |
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/// A random number generator based on the basic implementation of the PCG algorithm, |
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/// as described here: http://www.pcg-random.org/ |
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var PcgRandom = (function() { |
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'use strict'; |
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var defaultIncHi = 0x14057b7e; |
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var defaultIncLo = 0xf767814f; |
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/// Construct a random number generator. |
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function PcgRandom(seedHi, seedLo, incHi, incLo) { |
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this.setSeed(seedHi, seedLo, incHi, incLo) |
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} |
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/// Set the seed and incrementer. |
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PcgRandom.prototype.setSeed = function(seedHi, seedLo, incHi, incLo) { |
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if (seedLo == null && seedHi == null) { |
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seedLo = (Math.random() * 0xffffffff) >>> 0; |
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seedHi = 0; |
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} |
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else if (seedLo == null) { |
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seedLo = seedHi; |
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seedHi = 0; |
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} |
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if (incLo == null && incHi == null) { |
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incLo = this.state_ ? this.state_[3] : defaultIncLo; |
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incHi = this.state_ ? this.state_[2] : defaultIncHi; |
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} |
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else if (incLo == null) { |
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incLo = incHi; |
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incHi = 0; |
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} |
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this.state_ = new Int32Array([ 0, 0, incHi >>> 0, (incLo|1) >>> 0 ]); |
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this.next_(); |
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add64_(this.state_, this.state_[0], this.state_[1], seedHi>>>0, seedLo>>>0); |
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this.next_(); |
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return this; |
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}; |
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/// Return a copy of the internal state of this random number generator as a JavaScript Array. |
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PcgRandom.prototype.getState = function() { |
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return [this.state_[0], this.state_[1], this.state_[2], this.state_[3]]; |
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}; |
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/// Set the state of the random number generator. |
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PcgRandom.prototype.setState = function(state) { |
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this.state_[0] = state[0]; |
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this.state_[1] = state[1]; |
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this.state_[2] = state[2]; |
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this.state_[3] = state[3]|1; |
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}; |
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// shim for Math.imul. |
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var imul = Math.imul; |
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if (!imul) { |
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imul = function(a, b) { |
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var ah = (a >>> 16) & 0xffff, al = a & 0xffff; |
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var bh = (b >>> 16) & 0xffff, bl = b & 0xffff; |
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return ((al * bl) + (((ah * bl + al * bh) << 16) >>> 0) | 0); |
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}; |
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} |
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// multiply two 64 bit numbers (given in parts), and store the result in `out`. |
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function mul64_(out, aHi, aLo, bHi, bLo) { |
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var c1 = (aLo >>> 16) * (bLo & 0xffff) >>> 0; |
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var c0 = (aLo & 0xffff) * (bLo >>> 16) >>> 0; |
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var lo = ((aLo & 0xffff) * (bLo & 0xffff)) >>> 0; |
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var hi = ((aLo >>> 16) * (bLo >>> 16)) + ((c0 >>> 16) + (c1 >>> 16)) >>> 0; |
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c0 = (c0 << 16) >>> 0; |
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lo = (lo + c0) >>> 0; |
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if ((lo >>> 0) < (c0 >>> 0)) { |
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hi = (hi + 1) >>> 0; |
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} |
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c1 = (c1 << 16) >>> 0; |
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lo = (lo + c1) >>> 0; |
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if ((lo >>> 0) < (c1 >>> 0)) { |
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hi = (hi + 1) >>> 0; |
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} |
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hi = (hi + imul(aLo, bHi)) >>> 0; |
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hi = (hi + imul(aHi, bLo)) >>> 0; |
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out[0] = hi; |
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out[1] = lo; |
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} |
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// add two 64 bit numbers (given in parts), and store the result in `out`. |
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function add64_(out, aHi, aLo, bHi, bLo) { |
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var hi = (aHi + bHi) >>> 0; |
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var lo = (aLo + bLo) >>> 0; |
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if ((lo >>> 0) < (aLo >>> 0)) { |
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hi = (hi + 1) | 0; |
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} |
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out[0] = hi; |
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out[1] = lo; |
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} |
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var MUL_HI = 0x5851f42d >>> 0; |
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var MUL_LO = 0x4c957f2d >>> 0; |
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/// Generate a random 32 bit integer. This uses the PCG algorithm, described |
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/// here: http://www.pcg-random.org/ |
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PcgRandom.prototype.next_ = function() { |
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// save current state (what we'll use for this number) |
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var oldHi = this.state_[0] >>> 0; |
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var oldLo = this.state_[1] >>> 0; |
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// churn LCG. |
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mul64_(this.state_, oldHi, oldLo, MUL_HI, MUL_LO); |
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add64_(this.state_, this.state_[0], this.state_[1], this.state_[2], this.state_[3]); |
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// get least sig. 32 bits of ((oldstate >> 18) ^ oldstate) >> 27 |
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var xsHi = oldHi >>> 18; |
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var xsLo = ((oldLo >>> 18) | (oldHi << 14)) >>> 0; |
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xsHi = (xsHi ^ oldHi) >>> 0; |
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xsLo = (xsLo ^ oldLo) >>> 0; |
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var xorshifted = ((xsLo >>> 27) | (xsHi << 5)) >>> 0; |
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// rotate xorshifted right a random amount, based on the most sig. 5 bits |
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// bits of the old state. |
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var rot = oldHi >>> 27; |
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var rot2 = ((-rot >>> 0) & 31) >>> 0; |
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return ((xorshifted >>> rot) | (xorshifted << rot2)) >>> 0; |
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}; |
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/// Get a uniformly distributed 32 bit integer between [0, max). |
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PcgRandom.prototype.integer = function(max) { |
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if (!max) { |
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return this.next_(); |
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} |
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max = max >>> 0; |
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if ((max & (max - 1)) === 0) { |
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return this.next_() & (max - 1); // fast path for power of 2 |
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} |
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var num = 0; |
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var skew = ((-max >>> 0) % max) >>> 0; |
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for (num = this.next_(); num < skew; num = this.next_()) { |
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// this loop will rarely execute more than twice, |
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// and is intentionally empty |
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} |
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return num % max; |
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}; |
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var BIT_53 = 9007199254740992.0; |
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var BIT_27 = 134217728.0; |
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/// Get a uniformly distributed IEEE-754 double between 0.0 and 1.0, with |
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/// 53 bits of precision (every bit of the mantissa is randomized). |
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PcgRandom.prototype.number = function() { |
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var hi = (this.next_() & 0x03ffffff) * 1.0; |
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var lo = (this.next_() & 0x07ffffff) * 1.0; |
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return ((hi * BIT_27) + lo) / BIT_53; |
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}; |
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return PcgRandom; |
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}()); |
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if (typeof module !== 'undefined' && module.exports) { |
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module.exports = PcgRandom; |
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} |