andreis

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 shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname

logstash needs full time love.

There are roughly 70 code contributors to the logstash project as of today. Many more exist as helpful folks on IRC and the mailling list. Others post awesome bug reports and feature requests. The community is simply awesome.

I've been working on logstash for about 2 years. All as a hobby - all part-time. About 70% of the current content (commits, 'git blame' lines, etc) are by me.

Unfortunately, I've never used logstash in production. (Embarrassing, I know!)

I'm embarrassed to answer user questions like "How do I optimize elasticsearch's storage?" with "Sorry, I've never used elasticsearch outside of my laptop."

Partial Evaluation, Futamura Projection And Their Applications

What Partial Evaluation Is?

Partial evaluation means to fix some variables in the given code before execution. With a traditional implementation of a compiler or an interpreter, all variables are replaced with its value on each evaluation of that variable. This is because a variable can change at any timing. This is, however, not always true in actual applications. Almost all of large applications has setting variables and data

In August 2007 a hacker found a way to expose the PHP source code on facebook.com. He retrieved two files and then emailed them to me, and I wrote about the issue:

http://techcrunch.com/2007/08/11/facebook-source-code-leaked/

It became a big deal:

http://www.techmeme.com/070812/p1#a070812p1

The two files are index.php (the homepage) and search.php (the search page)

	var application_root = __dirname,
	express = require("express"),
	path = require("path"),
	mongoose = require('mongoose');

	var app = express.createServer();

	// database

	mongoose.connect('mongodb://localhost/ecomm_database');

	#!/bin/sh

	# Installs tarsnap client on Debian and Ubuntu
	#
	# You'll need to setup an account at
	# http://www.tarsnap.com
	# and load it with some funds
	#
	# Make sure you run this as root
	#

	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

	using System;
	using System.Collections.Generic;
	using System.Linq;
	using System.Text;

	namespace Scramble_test {
	public class Scrambler {

	UInt32 mask = 0;
	UInt32 value = 1;