Morgan Murrah airbr

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

Originally published in June 2008

When hiring Ruby on Rails programmers, knowing the right questions to ask during an interview was a real challenge for me at first. In 30 minutes or less, it's difficult to get a solid read on a candidate's skill set without looking at code they've previously written. And in the corporate/enterprise world, I often don't have access to their previous work.

To ensure we hired competent ruby developers at my last job, I created a list of 15 ruby questions -- a ruby measuring stick if you will -- to select the cream of the crop that walked through our doors.

What to expect

Candidates will typically give you a range of responses based on their experience and personality. So it's up to you to decide the correctness of their answer.

Project Title

One Paragraph of project description goes here

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes. See deployment for notes on how to deploy the project on a live system.

Prerequisites

The Problem

In Javascript this is bound in unexpected ways. Functions, in particular, create a new 'this' and so when you want to keep a reference to an "outer" object you sometimes see the pattern:

var self = this;

as in:

var self = this;

Common Options

-#, --progress-bar Make curl display a simple progress bar instead of the more informational standard meter.

-b, --cookie <name=data> Supply cookie with request. If no =, then specifies the cookie file to use (see -c).

-c, --cookie-jar <file name> File to save response cookies to.

#Understanding closures, callbacks and promises

For a code newbie like myself, callbacks, closures and promises are scary JavaScript concepts.

10 months into my full-time dev career, and I would struggle to explain these words to a peer.

So I decided it was time to face my fears, and try to get my head around each concept.

Here are the notes from my initial reading. I'll continue to refine them as my understanding improves.

	def colorize(value, color)
	case color
	when :black then "\e[30m" + value.to_s + "\e[0m"
	when :red then "\e[31m" + value.to_s + "\e[0m"
	when :green then "\e[32m" + value.to_s + "\e[0m"
	when :yellow then "\e[33m" + value.to_s + "\e[0m"
	when :blue then "\e[34m" + value.to_s + "\e[0m"
	when :magenta then "\e[35m" + value.to_s + "\e[0m"
	when :cyan then "\e[36m" + value.to_s + "\e[0m"
	when :white then "\e[37m" + value.to_s + "\e[0m"

	# ---------------------------------------------------------------------------
	#
	# Description: This file holds all my BASH configurations and aliases
	#
	# Sections:
	# 1. Environment Configuration
	# 2. Make Terminal Better (remapping defaults and adding functionality)
	# 3. File and Folder Management
	# 4. Searching
	# 5. Process Management

	/* bling.js */
	window.$ = document.querySelector.bind(document);
	window.$$ = document.querySelectorAll.bind(document);
	Node.prototype.on = window.on = function(name, fn) { this.addEventListener(name, fn); };
	NodeList.prototype.__proto__ = Array.prototype;
	NodeList.prototype.on = function(name, fn) { this.forEach((elem) => elem.on(name, fn)); };

	# Add the alias below to ~/.bash_profile on a Mac
	# Save the file and run: source ~/.bash_profile

	alias code='open $@ -a "Visual Studio Code"'