Jack Lu jackluson

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

To remove a submodule you need to:

Delete the relevant section from the .gitmodules file.
Stage the .gitmodules changes git add .gitmodules
Delete the relevant section from .git/config.
Run git rm --cached path_to_submodule (no trailing slash).
Run rm -rf .git/modules/path_to_submodule (no trailing slash).
Commit git commit -m "Removed submodule "
Delete the now untracked submodule files rm -rf path_to_submodule

	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

	import {
	WritableStream
	} from 'node:stream/web';
	import fs from 'fs'

	// https://stackoverflow.com/questions/73338326/how-can-i-save-a-file-i-download-using-fetch-with-fs/73338676#73338676

	const object = await getObject(file.filename)

	const download_write_stream = fs.createWriteStream(file.filename);

	import logging
	from threading import Thread

	device_ids = ["d1","d2","d3"]
	threads = []
	def get_logger(name, log_file, level=logging.INFO):
	handler = logging.FileHandler(log_file)
	formatter = logging.Formatter('[line:%(lineno)d] - %(levelname)s: %(message)s')
	handler.setFormatter(formatter)
	logger = logging.getLogger(name)

	import ReactDOM from 'react-dom';
	import { useEffect } from 'react';


	Modal._PortalStack = [] // 利用栈结构管理多个弹窗面板
	function Modal(Component) {
	function Portal(props?: any) {
	useEffect(() => {
	document.body.appendChild(Portal._container);
	return () => {