Lalit Kapoor lalitkapoor

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

	#!/bin/bash

	FAIL=0

	echo "starting"

	./sleeper 2 0 &
	./sleeper 2 1 &
	./sleeper 3 0 &
	./sleeper 2 0 &

	// See comments below.

	// This code sample and justification brought to you by
	// Isaac Z. Schlueter, aka isaacs

	// standard style
	var a = "ape",
	b = "bat",
	c = "cat",
	d = "dog",

	=Navigating=
	visit('/projects')
	visit(post_comments_path(post))

	=Clicking links and buttons=
	click_link('id-of-link')
	click_link('Link Text')
	click_button('Save')
	click('Link Text') # Click either a link or a button
	click('Button Value')

	var debug = require('util').debug;

	// helper prototype for rendering block scripts, stylesheet links, etc
	var blocktag = {
	toString: function() {
	var tag = this.tag,
	html = '<'+tag,
	that = this;

	Object.getOwnPropertyNames(this).forEach(function(prop) {

	<!DOCTYPE html>
	<html>
	<head>
	<title>tableToExcel Demo</title>
	<script src="tableToExcel.js"></script>
	</head>
	<body>

	<h1>tableToExcel Demo</h1>
	<p>Exporting the W3C Example Table</p>

	#!/usr/bin/env bash

	# Use this one-liner to produce a JSON literal from the Git log:

	git log \
	--pretty=format:'{%n "commit": "%H",%n "author": "%aN <%aE>",%n "date": "%ad",%n "message": "%f"%n},' \
	$@ \| \
	perl -pe 'BEGIN{print "["}; END{print "]\n"}' \| \
	perl -pe 's/},]/}]/'

	Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD

	#!/usr/bin/env bash
	curl https://s3.amazonaws.com/heroku-jvm-buildpack-vi/vim-7.3.tar.gz --output vim.tar.gz
	mkdir vim && tar xzvf vim.tar.gz -C vim
	export PATH=$PATH:/app/vim/bin

	BEGIN
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	ROLLBACK
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	COMMIT
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