Daniel Ribeiro danielribeiro

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

tmux cheat sheet

(C-x means ctrl+x, M-x means alt+x)

Prefix key

The default prefix is C-b. If you (or your muscle memory) prefer C-a, you need to add this to ~/.tmux.conf:

remap prefix to Control + a

Peter Thiel's CS183: Startup - Class 1 Notes Essay

Here is an essay version of my class notes from Class 1 of CS183: Startup. Errors and omissions are my own. Credit for good stuff is Peter’s entirely.

CS183: Startup—Notes Essay—The Challenge of the Future

Purpose and Preamble

Tech companies who have migrated to the JVM

NB: Does not include companies that started with a JVM language. The purpose of this gist is to list the companies that decided to move their stack (or some part of it) to the JVM.

Twitter (Ruby -> Scala) - http://www.readwriteweb.com/hack/2011/07/twitter-java-scala.php
Foursquare (PHP -> Scala) - http://www.scala-lang.org/node/5130
Facebook (PHP/C++ -> PHP on JVM) - http://nerds-central.blogspot.com.au/2012/08/facebook-moving-to-jvm.html
Tumblr (PHP -> Scala) - http://highscalability.com/blog/2012/2/13/tumblr-architecture-15-billion-page-views-a-month-and-harder.html
Square (Ruby -> Java/JRuby) - http://www.quora.com/Square-Inc-1/What-is-the-technology-stack-behind-Square

	// Lack of tail call optimization in JS
	var sum = function(x, y) {
	return y > 0 ? sum(x + 1, y - 1) :
	y < 0 ? sum(x - 1, y + 1) :
	x
	}

	sum(20, 100000) // => RangeError: Maximum call stack size exceeded

	// Using workaround

	* Only the releases of the stable versions are listed in principle. The releases of the unstable versions especially considered to be important are indicated as "not stable."
	* The branches used as the source of each releases are specified, and the branching timing of them are also shown. BTW, before subversionizing of the repository, the term called "trunk" was not used, but this list uses it in order to avoid confusion.
	* In order to show a historical backdrop, big conferences (RubyKaigi, RubyConf and Euruko) are also listed. About the venues of such conferences, general English notations are adopted, in my hope.
	* ruby_1_8_7 branch was recut from v1_8_7 tag after the 1.8.7 release because of an accident.
	* 1.2.1 release was canceled once, and the 2nd release called "repack" was performed. Although there were other examples similar to this, since the re-releases were performed during the same day, it does not write clearly in particular.
	* Since 1.0 was released with the date in large quantities, the mi

	module Example () where

	import Network.HTTP

	-- Non HTTPS

	-- 1. Perform a basic HTTP get request and return the body
	get :: String -> IO String
	get url = simpleHTTP (getRequest url) >>= getResponseBody

	(require 'clojure.test)

	(defmacro deftest*
	[name-string & body]
	(let [name-symbol
	(-> name-string
	clojure.string/lower-case
	(clojure.string/replace #"\W" "-")
	(clojure.string/replace #"-+" "-")
	(clojure.string/replace #"-$" "")

	{ "keys": ["home"], "command": "move_to", "args": {"to": "bol"} },
	{ "keys": ["end"], "command": "move_to", "args": {"to": "eol"} }