Steven stevenlordiam

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

Mac web developer apps

This gist's comment stream is a collection of webdev apps for OS X. Feel free to add links to apps you like, just make sure you add some context to what it does — either from the creator's website or your own thoughts.

— Erik

ANNOUNCEMENT

I have moved this over to the Tech Interview Cheat Sheet Repo and has been expanded and even has code challenges you can run and practice against!

\

移动开发团队 Objective-C 编码指南

Git Cheat Sheet

Commands

Getting Started

git init

or

Changing the default VM Path in VMWare Fusion on OSX Yosemite:

I had a little trouble figuring this out - so making a note of it. The VMWare Fusion default location for VMs is ~/Documents/Virtual Machines.localized, which doesnt work well for me as I typically have Documents symbolically linked to my Dropbox directory and prefer to move the default VM location rather than manage exclusions on every Dropbox install I have.

It's relatively straightforward on VMWare Workstation, and Oracle VirtualBox - but for some reason

	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

	{
	"Statement": [
	{
	"Sid": "PackerSecurityGroupAccess",
	"Action": [
	"ec2:CreateSecurityGroup",
	"ec2:DeleteSecurityGroup",
	"ec2:DescribeSecurityGroups",
	"ec2:AuthorizeSecurityGroupIngress",
	"ec2:RevokeSecurityGroupIngress"

	----- BEGIN LICENSE -----
	Andrew Weber
	Single User License
	EA7E-855605
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	942194A6 02396E98 E62C9979 4BB979FE
	91424C9D A45400BF F6747D88 2FB88078
	90F5CC94 1CDC92DC 8457107A F151657B
	1D22E383 A997F016 42397640 33F41CFC
	E1D0AE85 A0BBD039 0E9C8D55 E1B89D5D