Alex DeLorenzo alexdelorenzo

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

Problem: When linking to the raw version of a gist, the link changes with each revision.

Solution:

To return the first file from a gist: https://gist.github.com/[gist_user]/[gist_id]/raw/

Example: https://gist.github.com/atenni/5604522/raw/
Works even when you change the filename.

To get a file from multi–file gist: https://gist.github.com/[gist_user]/[gist_id]/raw/[file_name]

Operational PGP

This is a guide on how to email securely.

There are many guides on how to install and use PGP to encrypt email. This is not one of them. This is a guide on secure communication using email with PGP encryption. If you are not familiar with PGP, please read another guide first. If you are comfortable using PGP to encrypt and decrypt emails, this guide will raise your security to the next level.

Bash Shortcuts

Moving

command	description
ctrl + a	Goto BEGINNING of command line

	#Constants from sys/resources.h
	#I/O type
	#IOPOL_TYPE_DISK 0

	#scope
	#IOPOL_SCOPE_PROCESS 0
	#IOPOL_SCOPE_THREAD 1

	#I/O Priority
	#IOPOL_DEFAULT 0

	#!/bin/sh

	###
	# SOME COMMANDS WILL NOT WORK ON macOS (Sierra or newer)
	# For Sierra or newer, see https://github.com/mathiasbynens/dotfiles/blob/master/.macos
	###

	# Alot of these configs have been taken from the various places
	# on the web, most from here
	# https://github.com/mathiasbynens/dotfiles/blob/5b3c8418ed42d93af2e647dc9d122f25cc034871/.osx

	# Read the CMDLINE
	sudo ./rkflashtool r 0x0000 0x2000 > cmdline.txt

	# RESULT:
	# PARMWFIRMWARE_VER:4.0.4
	# MACHINE_MODEL:MID
	# MACHINE_ID:007
	# MANUFACTURER:RK30SDK
	# MAGIC: 0x5041524B
	# ATAG: 0x60000800

	Guide & Discussion Thread:

	http://forum.netkas.org/index.php?topic=874.0
	http://forum.netkas.org/index.php?action=printpage;topic=874.0

	For the best guide, use search keyword: chmod. Scrolls down to -->
	Post by: Shinso on September 18, 2012, 07:28:35 PM
	Post by: Shinso on September 18, 2012, 07:30:19 PM

	* First: upgrade cpu to Core2Duo

	#!/usr/bin/env zsh

	# Initialize VPN
	sudo vpnns up
	sudo vpnns start_vpn

	# Popcorn time!
	sudo ip netns exec frootvpn sudo -u $USER popcorntime

	# Cleanup

	"""
	This creates the following GIF, where the text appears to be "embedded"
	in the video and "disappears" behind rapunzel.

	http://i.imgur.com/gxEHfLX.gif
	"""

	from moviepy.editor import *
	import numpy as np
	import skimage.morphology as skm