webpack/lib/util/ParallelismFactorCalculator.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

const binarySearchBounds = require("../util/binarySearchBounds");

/** @typedef {function(number): void} Callback */

class ParallelismFactorCalculator {
	constructor() {
		/** @type {number[]} */
		this._rangePoints = [];
		/** @type {Callback[]} */
		this._rangeCallbacks = [];
	}

	/**
	 * @param {number} start range start
	 * @param {number} end range end
	 * @param {Callback} callback callback
	 * @returns {void}
	 */
	range(start, end, callback) {
		if (start === end) return callback(1);
		this._rangePoints.push(start);
		this._rangePoints.push(end);
		this._rangeCallbacks.push(callback);
	}

	calculate() {
		const segments = Array.from(new Set(this._rangePoints)).sort((a, b) =>
			a < b ? -1 : 1
		);
		const parallelism = segments.map(() => 0);
		const rangeStartIndices = [];
		for (let i = 0; i < this._rangePoints.length; i += 2) {
			const start = this._rangePoints[i];
			const end = this._rangePoints[i + 1];
			let idx = binarySearchBounds.eq(segments, start);
			rangeStartIndices.push(idx);
			do {
				parallelism[idx]++;
				idx++;
			} while (segments[idx] < end);
		}
		for (let i = 0; i < this._rangeCallbacks.length; i++) {
			const start = this._rangePoints[i * 2];
			const end = this._rangePoints[i * 2 + 1];
			let idx = rangeStartIndices[i];
			let sum = 0;
			let totalDuration = 0;
			let current = start;
			do {
				const p = parallelism[idx];
				idx++;
				const duration = segments[idx] - current;
				totalDuration += duration;
				current = segments[idx];
				sum += p * duration;
			} while (current < end);
			this._rangeCallbacks[i](sum / totalDuration);
		}
	}
}

module.exports = ParallelismFactorCalculator;