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

jboner

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

henrik

tmux cheatsheet

As configured in my dotfiles.

start new:

tmux

start new with session name:

protrolium

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

You can get the list of installed codecs with:

varyonic

# See https://codeship.com/documentation/docker/browser-testing/
FROM myapp:base

# We need wget to set up the PPA and xvfb to have a virtual screen and unzip to install the Chromedriver
RUN apt-get install -y wget xvfb unzip

# Set up the Chrome PPA
RUN wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -
RUN echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list

piscisaureus

Locate the section for your github remote in the .git/config file. It looks like this:

[remote "origin"]
	fetch = +refs/heads/*:refs/remotes/origin/*
	url = git@github.com:joyent/node.git

Now add the line fetch = +refs/pull/*/head:refs/remotes/origin/pr/* to this section. Obviously, change the github url to match your project's URL. It ends up looking like this:

sudara

# this monit config goes in /etc/monit/conf.d

check process puma_master
  with pidfile  /data/myapp/current/tmp/puma.pid
  start program = "/etc/monit/scripts/puma start"
  stop program = "/etc/monit/scripts/puma stop" 
  group myapp

check process puma_worker_0
  with pidfile /data/myapp/current/tmp/puma_worker_0.pid

nazgob

# you have ctags but it does not work...
$ ctags -R --exclude=.git --exclude=log *
ctags: illegal option -- R
usage: ctags [-BFadtuwvx] [-f tagsfile] file ...

#you need to get new ctags, i recommend homebrew but anything will work
$ brew install ctags

#alias ctags if you used homebrew
$ alias ctags="`brew --prefix`/bin/ctags"

andruby

after "deploy:symlink", "deploy:restart_workers"

##
# Rake helper task.
# http://pastie.org/255489
# http://geminstallthat.wordpress.com/2008/01/27/rake-tasks-through-capistrano/
# http://ananelson.com/said/on/2007/12/30/remote-rake-tasks-with-capistrano/
def run_remote_rake(rake_cmd)
  rake_args = ENV['RAKE_ARGS'].to_s.split(',')
  cmd = "cd #{fetch(:latest_release)} && #{fetch(:rake, "rake")} RAILS_ENV=#{fetch(:rails_env, "production")} #{rake_cmd}"

mdouze

###########################################
# serialization of indexes to byte arrays
###########################################

def serialize_index(index):
    """ convert an index to a numpy uint8 array  """
    writer = faiss.VectorIOWriter()
    faiss.write_index(index, writer)
    return faiss.vector_to_array(writer.data)