Alex Kwiatkowski rupurt

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

#launchd Usage

I have a bash script called foo.sh that takes one command line argument, bar. I want it to run every 60 seconds and load at startup.

an XML plist is Apple Property List
com.mydomain.foo.plist Name of launchd plist file should be a reverse fqdn, like (this may not be required, but convention)
com.mydomain.foo.plist lives in $HOME/Library/LaunchAgents and is ran as that user.
com.mydomain.foo.plist can also live /Library/LaunchDaemons or /Library/LaunchAgents, have requirements, ran as root
Load plist with launchctl load com.mydomain.foo.plist
Unload plist with lauchctl unload com.mydomain.foo.plist

How to setup your own CA with OpenSSL

For educational reasons I've decided to create my own CA. Here is what I learned.

First things first

Lets get some context first.

Big List of Real Estate APIs

Listings / Property Data

####Rets Rabbit http://www.retsrabbit.com

Rets Rabbit removes the nightmare of importing thousands of real estate listings and photos from RETS or ListHub and gives you an easy to use import and Web API server so you can focus on building your listing search powered website or app.

Guide to your first Tree-sitter grammar

NOTE: The Tree-sitter API and documentation has changed and improved since this guide was created. I can't guarantee this is up to date.

About

Tree-sitter is the new way Atom is providing language recognition features, such as syntax highlighting, code folding, autocomplete, and more. In contrast to TextMate grammars, which work by regex matching, Tree-sitter will generate an entire syntax tree. But more on that can be found in it's own docs.

Here, we look at making one from scratch.

This is a quick sketch of how I think terminology applies to the various kinds of mocking and test doubles that apply in Go.

In practice, the most effective way to mock things in Go is to use an interface, and then to substitute a specialized testing implementation in place of a real one. Wherever a substitute is used, I think this should be called a "double".

There is one specialization of a "double" and that is a "fake" implementation. Fakes can often have real world uses, e.g: "RamDiskDatabase", but are typically

	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

	# Here's a contrived example of a LEFT JOIN using ARel. This is an example of
	# the mechanics, not a real-world use case.

	# NOTE: In the gist comments, @ozydingo linked their general-purpose ActiveRecord
	# extension that works for any named association. That's what I really wanted!
	# Go use that! Go: https://gist.github.com/ozydingo/70de96ad57ab69003446

	# == DEFINITIONS
	# - A Taxi is a car for hire. A taxi has_many :passengers.
	# - A Passenger records one person riding in one taxi one time. It belongs_to :taxi.

	/*
	* client.c
	*
	* Simple FTP Client
	* ====================
	* Connects the server, and sends a command "Get FILENAME" to retrieve
	* the file. If the file exists on the server, client retrieves it.
	*
	* Compile & link : gcc client.c -o client
	* Execute : ./client

	# One liner
	wget --recursive --page-requisites --adjust-extension --span-hosts --convert-links --restrict-file-names=windows --domains yoursite.com --no-parent yoursite.com

	# Explained
	wget \
	--recursive \ # Download the whole site.
	--page-requisites \ # Get all assets/elements (CSS/JS/images).
	--adjust-extension \ # Save files with .html on the end.
	--span-hosts \ # Include necessary assets from offsite as well.
	--convert-links \ # Update links to still work in the static version.