hellerbarde

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

mattlewissf

git add -p is your friend

git add -p is basically "git add partial (or patch)"

Patch mode allows you to stage parts of a changed file, instead of the entire file. This allows you to make concise, well-crafted commits that make for an easier to read history. This feature can improve the quality of the commits. It also makes it easy to remove parts of the changes in a file that were only there for debugging purposes - prior to the commit without having to go back to the editor.

It allows you to see the changes (delta) to the code that you are trying to add, and lets you add them (or not) separately from each other using an interactive prompt. Here's how to use it:

from the command line, either use

• git add -p

abdullin

This is my response to an email asking about Domain-Driven Design in golang project.

Thank you for getting in touch. Below you will find my thoughts on how golang works with DDD, changing it. This is merely a perception of how things worked out for us in a single project.

That project has a relatively well-known domain. My colleagues on this project are very knowledgeable, thoughtful and invested in quality design. The story spelled out below is a result of countless hours spent discussing and refining the approach.

Conclusions could be very different, if there was a different project, team or a story-teller.

Short story

akras14

Git Cheat Sheet

Commands

Getting Started

git init

or

markerikson

[02:06 PM] acemarke: @Steven : a couple other thoughts on the whole NODE_ENV thing. First, per my comments, it really is a Node concept. It's a system environment variable that Node exposes to your application, and apparently the Express web server library popularized using its value to determine whether to do optimizations or not
[02:08 PM] acemarke: Second, because of its use within the Node ecosystem, web-focused libraries also started using it to determine whether to they were being run in a "development" environment vs a "production" environment, with corresponding optimizations. For example, React uses that as the equivalent of a C #ifdef to act as conditional checking for debug logging and perf tracking. If process.env.NODE_ENV is set to "production", all those if clauses will evaluate to false.
Third, in conjunction with a tool like UglifyJS that does minification and removal of dead code blocks, a clause that is surrounded with if(process.env.NODE_ENV !== "development")

celso

syntax on
set ruler               " Show the line and column numbers of the cursor.
set formatoptions+=o    " Continue comment marker in new lines.
set textwidth=0         " Hard-wrap long lines as you type them.
set modeline            " Enable modeline.
set esckeys             " Cursor keys in insert mode.
set linespace=0         " Set line-spacing to minimum.
set nojoinspaces        " Prevents inserting two spaces after punctuation on a join (J)
" More natural splits
set splitbelow          " Horizontal split below current.

liangfu

ffmpeg

Converting Audio into Different Formats / Sample Rates

Minimal example: transcode from MP3 to WMA:
ffmpeg -i input.mp3 output.wma

You can get the list of supported formats with:
ffmpeg -formats

Convert WAV to MP3, mix down to mono (use 1 audio channel), set bit rate to 64 kbps and sample rate to 22050 Hz:

gaearon

Note:

When this guide is more complete, the plan is to move it into Prepack documentation.
For now I put it out as a gist to gather initial feedback.

A Gentle Introduction to Prepack (Part 1)

If you're building JavaScript apps, you might already be familiar with some tools that compile JavaScript code to equivalent JavaScript code:

• Babel lets you use newer JavaScript language features, and outputs equivalent code that targets older JavaScript engines.

ryanflorence

""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
" Font
:set guifont=Source\ Code\ Pro:h14

""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
" Hide pointless junk at the bottom, doesn't work in .vimrc for some reason?
:set laststatus=0
:set noshowmode "don't show --INSERT--
:set noruler "don't show line numbers/column/% junk

HadrienG2

Hello, Rust community!

My name is Hadrien and I am a software performance engineer in a particle physics lab. My daily job is to figure out ways to make scientific software use hardware more efficiently without sacrificing its correctness, primarily by adapting old-ish codebases to the changes that occured in the software and computing landscape since the days where they were designed:

• CPU clock rates and instruction-level parallelism stopped going up, so optimizing code is now more important.
• Multi-core CPUs went from an exotic niche to a cheap commodity, so parallelism is not optional anymore.
• Core counts grow faster than RAM prices go down, so multi-processing is not enough anymore.
• SIMD vectors become wider and wider, so vectorization is not a gimmick anymore.