Aidar Nugmanoff nugmanoff

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

ANNOUNCEMENT

I have moved this over to the Tech Interview Cheat Sheet Repo and has been expanded and even has code challenges you can run and practice against!

\

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

Overview

This is a bash script that will automatically turn your wifi off if you connect your computer to an ethernet connection and turn wifi back on when you unplug your ethernet cable/adapter. If you decide to turn wifi on for whatever reason, it will remember that choice. This was improvised from this mac hint to work with Yosemite, and without hard-coding the adapter names. It's supposed to support growl, but I didn't check that part. I did, however, add OSX notification center support. Feel free to fork and fix any issues you encounter.

Most the credit for these changes go to Dave Holland.

Requirements

Mac OSX 10+
Administrator privileges

I'm learning about SOPS and setting it up as my preferred mechanism for storing secrets. Here are my notes.

PGP

It’s security mechanism is that we (i.e. client) use a PUBLIC key from the receiver (i.e. server) and encode it with a random key (I’m saying nonce but it could be reused)

This varies from RSA and SSH because the server uses a PUBLIC key to identify the client.

Web of trust

Web of trust operates by still using PGP (i.e. encoding with recipient’s public key) but additionally, we can encrypt/sign the data as our own by signing it with the client’s private key.

This means the recipient will initially decrypt via our (i.e. client’s) public key (verifying the source) and then decrypting via their (i.e. server’s) private key to get the data.

Create a bootable installer for macOS

The following instructions were predominantly sourced via this Apple Support Document.

With macOS, you can use a USB flash drive or other removable media as a startup disk from which to install macOS. These advanced steps are intended primarly for system administrators and others who are familiar with the command line.

The final executable command(s) are found within Section III. Final macOS Executable Commands labled as Full Example or Full Example w/Options. I personally use the w/Options command which include both the --nointeraction and &&say Installation commands.

	var EventYouTubeVideo = (function(){
	var module = {};

	module.init = function(){
	var tag = document.createElement('script');
	tag.src = "http://www.youtube.com/iframe_api";
	var firstScriptTag = document.getElementsByTagName('script')[0];
	firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);
	};

	WITH table_scans as (
	SELECT relid,
	tables.idx_scan + tables.seq_scan as all_scans,
	( tables.n_tup_ins + tables.n_tup_upd + tables.n_tup_del ) as writes,
	pg_relation_size(relid) as table_size
	FROM pg_stat_user_tables as tables
	),
	all_writes as (
	SELECT sum(writes) as total_writes
	FROM table_scans

	var player;

	// this function gets called when API is ready to use
	function onYouTubePlayerAPIReady() {
	// create the global player from the specific iframe (#video)
	player = new YT.Player('player', {
	events: {
	// call this function when player is ready to use
	'onReady': onPlayerReady,
	'onStateChange': onPlayerStateChange

	/* -fno-objc-arc
	CFTypeRef _unsafeCreatePartiallyInitialized(Class c) {
	Method method = class_getInstanceMethod([NSObject class], @selector(init));
	IMP imp = method_getImplementation(method);
	return ((id (*)(id, SEL))imp)([c alloc], @selector(init));
	}

	void _unsafeDestructPartiallyInitialized(CFTypeRef x) {
	Method method = class_getInstanceMethod([NSObject class], @selector(dealloc));
	IMP imp = method_getImplementation(method);