Abdullah Barrak abarrak

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

Creating a Happy Git Environment on OS X

Step 1: Install Git

brew install git bash-completion

Configure things:

git config --global user.name "Your Name"

git config --global user.email "you@example.com"

In my previous post I described how to securely acquire the Mozilla list of root certificates and convert them to a form usable by curl and various libraries which don't ship with them.

Next, I want to point Net:HTTP at this file library-wide, so that it is used by all invocations of methods accessing https resources (in particular, Kernel#open, which in ruby 1.8.7 does not have a ca_file option and is therefore unusable with https). I hunted around the ruby standard library for a couple hours and came up with this:

require 'open-uri'
require 'net/https'

module Net
 class HTTP

	# Chained comparisons in Ruby
	# inspired by http://coffeescript.org/#comparisons
	# as well as http://refactormycode.com/codes/1284

	[:<, :>, :<=, :>=].each do \|operator\|
	[Float, Fixnum, Rational, Comparable].each do \|klass\|
	klass.class_eval do
	alias_method "_#{operator}", operator
	define_method operator do \|rhs\|
	send("_#{operator}", rhs) && rhs

	<div id='tag_cloud'>
	{% for tag in site.tags %}
	<a href="#{{ tag[0] }}" title="{{ tag[0] }}" rel="{{ tag[1].size }}">{{ tag[0] }}</a>
	{% endfor %}
	</div>

	<ul id='tag_list'>
	{% for tag in site.tags %}
	<li class='tag_item' id='{{ tag[0] }}'>
	<span class='tag_name'>{{ tag[0] }}</span>