Michal Bernhard michalbcz

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

Sort the characters in the following string:

abcdefghijklmnopqrstuvwxyz_

by the number of times the character appears in the following text (descending):

Note: the text scrolls.

	const puppeteer = require('puppeteer')
	const fs = require('fs')

	// this wrapper means immediatelly execute this code
	void(async () => {
	const url = 'https://zbranekvalitne.cz/zbrojni-prukaz/testove-otazky'

	try {
	console.log("I am scraping questions from " + url)
	const browser = await puppeteer.launch({

	import java.io.InputStreamReader;
	import java.io.Reader;
	import java.net.URL;
	import java.net.URLConnection;

	import javax.net.ssl.HostnameVerifier;
	import javax.net.ssl.HttpsURLConnection;
	import javax.net.ssl.SSLContext;
	import javax.net.ssl.SSLSession;
	import javax.net.ssl.TrustManager;

	import org.apache.commons.io.IOUtils;

	import java.io.IOException;
	import java.io.InputStream;
	import java.net.Authenticator;
	import java.net.InetSocketAddress;
	import java.net.PasswordAuthentication;
	import java.net.Proxy;
	import java.net.SocketAddress;
	import java.net.URL;

	"use strict";

	var API_KEY = '__API_KEY__';
	var PHOTOSET_IDS = ['__ID1__', '__ID2__', '__ID3__'];

	var cartagenaApp = angular.module('cartagenaApp');

	cartagenaApp.directive('flickrBackground', function(Flickr, $http) {
	var _flickrBackground = function($scope, $element) {
	var nextPhoto;

	SSLContext sslContext = null;
	try {
	sslContext = SSLContext.getInstance("TLS");
	sslContext.init(null, new TrustManager[] { new SSLTrustManger() }, new java.security.SecureRandom());
	} catch (Exception e) {
	throw new RuntimeException(e);
	}
	SSLSocketFactory socketFactory = sslContext.getSocketFactory();

	import static org.apache.commons.lang3.StringUtils.isEmpty;

	public class StringUtils {

	/**
	* unicode aware version of Apache Common's StringUtils#strip
	*/
	public static String strip(String str) {
	if (isEmpty(str)) {
	return str;