Samuel Huang huangsam

People

`:bowtie:`	😄 `:smile:`	😆 `:laughing:`
😊 `:blush:`	😃 `:smiley:`	☺️ `:relaxed:`
😏 `:smirk:`	😍 `:heart_eyes:`	😘 `:kissing_heart:`
😚 `:kissing_closed_eyes:`	😳 `:flushed:`	😌 `:relieved:`
😆 `:satisfied:`	😁 `:grin:`	😉 `:wink:`
😜 `:stuck_out_tongue_winking_eye:`	😝 `:stuck_out_tongue_closed_eyes:`	😀 `:grinning:`
😗 `:kissing:`	😙 `:kissing_smiling_eyes:`	😛 `:stuck_out_tongue:`

How does `ls` work?

I wanted to be really able to explain to a fair amount of detail how does the program :command:`ls` actually work right from the moment you type the command name and hit ENTER. What goes on in user space and and in kernel space? This is my attempt and what I have learned so far on Linux (Fedora 19, 3.x kernel).

How does the shell find the location of 'ls' ?

Easy parallel python with concurrent.futures

As of version 3.3, python includes the very promising concurrent.futures module, with elegant context managers for running tasks concurrently. Thanks to the simple and consistent interface you can use both threads and processes with minimal effort.

For most CPU bound tasks - anything that is heavy number crunching - you want your program to use all the CPUs in your PC. The simplest way to get a CPU bound task to run in parallel is to use the ProcessPoolExecutor, which will create enough sub-processes to keep all your CPUs busy.

We use the context manager thusly:

with concurrent.futures.ProcessPoolExecutor() as executor:

Gerrit vs Github: for code review and codebase management

Sure, Github wins on the UI. Hands down. But, despite my initial annoyance with Gerrit when I first started using it almost a year ago, I am now a convert. Fully. Let me tell you why.

Note: This is an opinionated (on purpose) piece. I assume your preferences are like mine on certain ideas, such as:

Fast-forward submits to the target branch are better than allowing merge commits to the target branch. The reason I personally prefer this is that, even if a non-conflicting merge to the target branch is possible, the fact that the review/pull request is not up to date with the latest on the target branch means feature branch test suite runs in the CI pipeline reporting on the review/PR may not be accurate. Another minor point is that forced merge commits are annoying as fuck (opinion) and clutter up Git log histories unnecessarily and I prefer clean histories.
Atomic/related changes all in one commit is something worth striving for. Having your dev

Note: these are pretty rough notes I made for my team on the fly as I was reading through some pages. Some could be mildly inaccurate but hopefully not terribly so. I might resort to convenient fiction & simplification sometimes.

My top contenders, mostly based on popularity / community etc:

Angular
Backbone
React
Ember

Mostly about MVC (or derivatives, MVP / MVVM).

This guide assumes that you recently run brew upgrade postgresql and discovered to your dismay that you accidentally bumped from one major version to another: say 9.3.x to 9.4.x. Yes, that is a major version bump in PG land.

First let's check something.

brew info postgresql

The top of what gets printed as a result is the most important:

	=Navigating=
	visit('/projects')
	visit(post_comments_path(post))

	=Clicking links and buttons=
	click_link('id-of-link')
	click_link('Link Text')
	click_button('Save')
	click('Link Text') # Click either a link or a button
	click('Button Value')

	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

	// === Arrays

	var [a, b] = [1, 2];
	console.log(a, b);
	//=> 1 2


	// Use from functions, only select from pattern
	var foo = () => [1, 2, 3];

Samuel Huang huangsam

How does ls work?

Easy parallel python with concurrent.futures

Gerrit vs Github: for code review and codebase management

How does `ls` work?