Jinhai ZHOU JinhaiZ

操作	延迟(纳秒)	延迟(微秒)	参考
CPU L1 级缓存访问	0.5 ns
分支预测错误*	5 ns
CPU L2 级缓存访问	7 ns		14x L1 cache
互斥体Mutex 加锁/解锁	25 ns
内存访问	100 ns		20x L2 cache, 200x L1 cache
用Zippy压缩1K字节	3,000 ns	3 us
在1 Gbps速率的网络上发送1K字节 over	10,000 ns	10 us
从SSD读取4K长度的随机数据	150,000 ns	150 us	~1GB/sec SSD

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Direct Ethernet connection to Raspberry Pi/Odroid without router

The solution is based on running DHCP service at your workstation (your notebook for example), and use it to attribute an IP address to your Raspberry Pi/Odroid. Then use ssh to connect to your Raspberry Pi/Odroid through this IP address.

Terminology	Explaination
Client	Your Single Board Computer, such as a Raspberry Pi or an Odroid
Server	Your workstation with any linux based systems, like Ubuntu

Download Kubectl

Download the lastest release

 `curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl`

Make it executable

chmod +x ./kubectl

Server side

install ssh server
```
sudo apt-get install openssh-server
```

Client side

Algo

Converting multiple BMPs to an AVI without compression

You can use the huffyuv encoder to create a lossless output:

ffmpeg -i img%d.jpg -vcodec huffyuv output.avi

	import pymongo

	connection = pymongo.MongoClient('localhost', 27017)
	db = connection['db_name']
	collection = db['collection_name']

	# now we can do CRUD operations with this collection pointer
	collection.find({})

	# download an entire directory from a web site
	# -r Turn on recursive retrieving. The default maximum depth is 5.
	# --no-parent Do not ever ascend to the parent directory when retrieving recursively.
	wget -r --no-parent http://formations.telecom-bretagne.eu/syst/TPDIST/Additional-Reading/
	# use wget with username and password
	wget -r --no-parent --user user_name --password my_pwd http://formations.telecom-bretagne.eu/syst/TPDIST/Additional-Reading/

	# install Scrapy
	sudo apt-get install libffi-dev
	sudo apt-get install libxml2-dev
	sudo apt-get install libxslt1-dev
	sudo apt-get install python-dev
	sudo pip install scrapy

	# install MongoDB
	sudo apt-get update
	sudo apt-get install mongodb-server

	from sshtunnel import SSHTunnelForwarder
	import pymongo

	MONGO_HOST = "IP_ADDRESS"
	MONGO_USER = "USERNAME"
	MONGO_PASS = "PASSWORD"
	MONGO_DB = "DATABASE_NAME"
	MONGO_COLLECTION = "COLLECTION_NAME"

	# define ssh tunnel