estimate-padding-overhead.js

"use strict";

const D = 20 * 1024;
const rMax = 100 * 1024;
const resourceSize = D + 500;
const observations = [];
const numRequests = 50;
const overhead = [];

function roundUp(value) {
	return Math.ceil(value/D) * D;
}

function getRandom() {
	return Math.floor(Math.random() * rMax);
}

for (let j = 0; j < 100000; j++) {
	const measurements = [];
	for (let i = 0; i < numRequests; i++) {
		measurements.push(roundUp(resourceSize + getRandom()))
	}
	const ratio = measurements.filter(function(x) {
		return x === roundUp(resourceSize);
	}).length / measurements.length;
	observations.push(roundUp(resourceSize) - ratio * rMax);
	overhead.push.apply(overhead, measurements.map(function(x) {return x - resourceSize}));
}
const avgOff = observations.reduce(function(totalDiff, x) {
	return totalDiff + Math.abs(x - resourceSize); 
}, 0) / observations.length;
const avgOverhead = overhead.reduce(function(x, y){return x+y}) / overhead.length;

console.log('On average, the measurements using', numRequests, 'requests, is off by', avgOff.toFixed(2), 'bytes, for D =', D, ', rMax =', rMax);
console.log('Average "overhead":', avgOverhead.toFixed(2), "bytes");