Jim Shu cwshu

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

前端工程師面試問題集

@版本 2.0.0

譯注：此翻譯版，主要給不能流利的讀英文的人看，相關專有名詞還是保留原文。翻譯不好地方請協助pull request.

此repository包含了一些前端開發的面試問題，來審查一個有潛力的面試者。這並不是建議你對同一個面試者問上所有的問 (那會花費好幾小時)。從列表中挑幾個題目，應該就夠幫助你審查面試者是否擁有你需要的技能。

Rebecca Murphey 的 Baseline For Front-End Developers 也是一篇很棒且值得讀的文章在你開始面試之前。

Connecting to serial port (com port) over network

(Serial port or com port? - Serial ports are often refered as COM ports. It is the same to be short. You can read abut it in the Wiki article )

The problem
The solution in theory
WINDOWS
- Server
- Client

Driver Signature

Using `<details>` in GitHub

Suppose you're opening an issue and there's a lot noisey logs that may be useful.

Rather than wrecking readability, wrap it in a <details> tag!

<details>
 Summary Goes Here

this has been rewritten yet again as most workarounds aren't required anymore since wine 3+

example video of the final result: https://www.youtube.com/watch?v=zkqzQoeOGfU

with touchscreen: https://www.youtube.com/watch?v=GcIrlorWmaQ

performance is indistinguishable from windows. there might be a very slight ~25ms sound latency which is easily compensated with +25 local offset

tested on

	import fcntl
	import os
	import struct
	import subprocess


	# Some constants used to ioctl the device file. I got them by a simple C
	# program.
	TUNSETIFF = 0x400454ca
	TUNSETOWNER = TUNSETIFF + 2

	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

	// define a grammar called Hello
	grammar Hello;
	r : 'hello' ID;
	ID : [a-z]+ ;
	WS : [ \t\r\n]+ -> skip ;