93 lines
2.8 KiB
JavaScript
93 lines
2.8 KiB
JavaScript
"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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const BinaryHeap_1 = require("./BinaryHeap");
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const units_1 = require("./units");
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class ExponentiallyDecayingSample {
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constructor(options) {
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this.RESCALE_INTERVAL = 1 * units_1.default.HOURS;
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this.ALPHA = 0.015;
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this.SIZE = 1028;
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options = options || {};
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this._elements = new BinaryHeap_1.default({
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score: function (element) {
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return -element.priority;
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}
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});
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this._rescaleInterval = options.rescaleInterval || this.RESCALE_INTERVAL;
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this._alpha = options.alpha || this.ALPHA;
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this._size = options.size || this.SIZE;
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this._random = options.random || this._random;
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this._landmark = null;
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this._nextRescale = null;
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this._mean = null;
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}
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update(value, timestamp) {
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const now = Date.now();
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if (!this._landmark) {
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this._landmark = now;
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this._nextRescale = this._landmark + this._rescaleInterval;
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}
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timestamp = timestamp || now;
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const newSize = this._elements.size() + 1;
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const element = {
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priority: this._priority(timestamp - this._landmark),
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value: value
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};
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if (newSize <= this._size) {
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this._elements.add(element);
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}
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else if (element.priority > this._elements.first().priority) {
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this._elements.removeFirst();
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this._elements.add(element);
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}
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if (now >= this._nextRescale)
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this._rescale(now);
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}
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toSortedArray() {
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return this._elements
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.toSortedArray()
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.map(function (element) {
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return element.value;
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});
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}
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toArray() {
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return this._elements
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.toArray()
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.map(function (element) {
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return element.value;
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});
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}
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_weight(age) {
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return Math.exp(this._alpha * (age / 1000));
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}
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_priority(age) {
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return this._weight(age) / this._random();
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}
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_random() {
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return Math.random();
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}
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_rescale(now) {
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now = now || Date.now();
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const self = this;
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const oldLandmark = this._landmark;
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this._landmark = now || Date.now();
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this._nextRescale = now + this._rescaleInterval;
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const factor = self._priority(-(self._landmark - oldLandmark));
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this._elements
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.toArray()
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.forEach(function (element) {
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element.priority *= factor;
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});
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}
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avg(now) {
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let sum = 0;
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this._elements
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.toArray()
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.forEach(function (element) {
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sum += element.value;
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});
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return (sum / this._elements.size());
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}
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}
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exports.default = ExponentiallyDecayingSample;
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