Leandro Moreira leandromoreira

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

OS X Screencast to animated GIF

This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.

Instructions

To capture the video (filesize: 19MB), using the free "QuickTime Player" application:

	--
	-- vardump
	-- original verstion by Tobias Sulzenbruck and Christoph Beckmann
	-- source: Lua Gems, page 29
	-- modifications: Krishna Kotecha
	--

	--[[
	value - the value to dump

	-- Print contents of `tbl`, with indentation.
	-- `indent` sets the initial level of indentation.
	function tprint (tbl, indent)
	if not indent then indent = 0 end
	for k, v in pairs(tbl) do
	formatting = string.rep(" ", indent) .. k .. ": "
	if type(v) == "table" then
	print(formatting)
	tprint(v, indent+1)
	else

	import time
	import socket
	def collect_metric(name, value, timestamp):
	sock = socket.socket()
	sock.connect( ("localhost", 2003) )
	sock.send("%s %d %d\n" % (name, value, timestamp))
	sock.close()

	def now():
	return int(time.time())

	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>

	/*
	* MCrypt API available online:
	* http://linux.die.net/man/3/mcrypt
	*/
	#include <mcrypt.h>

	# app/models/ability.rb

	# All front end users are authorized using this class
	class Ability
	include CanCan::Ability

	def initialize(user)
	user \|\|= AdminUser.new
	case user.role
	when "admin"

	(ns collatz.core)

	(defn collatz
	"Given n, it returns n/2 if it's even or n*3+1 if it's odd."
	[n]
	(if (even? n)
	(/ n 2)
	(+ (* 3 n) 1)))

	(declare count-steps-of-collatz)

	<!doctype html>
	<html ng-app="myApp">
	<head>
	<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.5/angular.min.js"></script>
	</head>
	<body>

	<div ng-controller="TodoCtrl">
	<button ng-click="beQuickOrBeDead()">Fetch with 100ms timeout</button>
	<button ng-click="neverEndingStory()">Fetch with default timeout</button>