Cooper Pellaton cooperpellaton

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

How-to setup a simple git push deployment

These are my notes basically. At first i created this gist just as a reminder for myself. But feel free to use this for your project as a starting point. If you have questions you can find me on twitter @thomasf https://twitter.com/thomasf This is how i used it on a Debian Wheezy testing (https://www.debian.org/releases/testing/)

Discuss, ask questions, etc. here https://news.ycombinator.com/item?id=7445545

On the server (example.com)

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

In this article, I will share some of my experience on installing NVIDIA driver and CUDA on Linux OS. Here I mainly use Ubuntu as example. Comments for CentOS/Fedora are also provided as much as I can.

GDB for the Uninitiated

Overview

You're working on a C project for CS 2200. There's 2 days left before the assignment is due and for some reason, you're getting a segmentation fault after writing your last function. You've looked over your code 23 times but you just can't figure out where the bug is! Giving up and calling it a day, you decide to go to office hours and ask a TA for help.

If it sounds like this might be you in the near future, then allow me to run through a typical scenario for what happens when you come in and ask for help. You'll sit down, wait for 30 minutes while the TAs get through the queue of students asking questions, and finally notice that it's your turn next. The TA will walk over and ask you what's up. You'll explain that your code is seg-faulting and for the life of you, you can't figure out why. So the TA will take a quick peak at your code for any obvious errors, and then ask you the following question:

Did you run it through GDB?

	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

	/*
	SafariHack
	==========

	Use with SIMBL or compatible extension like EasySIMBL. Only tested on OS X 10.10.

	LICENSE
	-------

	Copyright (c) 2014 Yoshimasa Niwa

	# Make sure you grab the latest version
	curl -OL https://github.com/google/protobuf/releases/download/v3.2.0/protoc-3.2.0-linux-x86_64.zip

	# Unzip
	unzip protoc-3.2.0-linux-x86_64.zip -d protoc3

	# Move protoc to /usr/local/bin/
	sudo mv protoc3/bin/* /usr/local/bin/

	# Move protoc3/include to /usr/local/include/

	#!/bin/bash

	set -e

	CONTENTS=$(tesseract -c language_model_penalty_non_dict_word=0.8 --tessdata-dir /usr/local/share/tessdata/ "$1" stdout -l eng \| xml esc)

	hex=$((cat <<EOF
	<?xml version="1.0" encoding="UTF-8"?>
	<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
	<plist version="1.0">

	# List of packages to be installed.
	$Packages = 'firefox', 'vlc', '7zip', 'vscode', `
	'everything', 'sharex', 'scansnapmanager', 'steam', 'discord', `
	'Revo.Uninstaller', 'battle.net'
	# Packages that won't be installed and the user will be reminded of.
	$Extras = "Windows Store apps, Oculus, AMD/Radeon Drivers"

	# Get the ID and security principal of the current user account
	$myWindowsID = [System.Security.Principal.WindowsIdentity]::GetCurrent()
	$myWindowsPrincipal = new-object System.Security.Principal.WindowsPrincipal($myWindowsID)