Daniel cndaniel

Falsehoods programmers believe about time

This is a compiled list of falsehoods programmers tend to believe about working with time.

Don't re-invent a date time library yourself. If you think you understand everything about time, you're probably doing it wrong.

Falsehoods

There are always 24 hours in a day.
February is always 28 days long.
Any 24-hour period will always begin and end in the same day (or week, or month).

De-'Async Inject' Universal Analytics

This gist applies the theory from Ilya Grigorik's Script-injected "async scripts" considered harmful on the default Universal Analytics snippet. TLDR place this above the CSS in the <head> of your document

<!-- Google Analytics Part 1: Creates window.ga, sets account, and queues pageview-->
<script>
  !function(n,t){n.GoogleAnalyticsObject=t,n[t]=n[t]||function(){(n[t].q=n[t].q||[]).push(arguments)},n[t].l=1*new Date}(window,"ga");
  ga('create', 'UA-XXXX-Y', 'auto'); // REPLACE UA-XXXX-Y w/ YOUR ACCOUNT
 ga('send', 'pageview');

	#!/bin/bash
	#
	# This macOS bash script helps you initialize a new Shadowsocks server with doctl in seconds.
	# Original author: lexrus https://github.com/lexrus
	#
	# You can get $100 free credit for create VPS in DigitalOcean with my referral link:
	# https://m.do.co/c/3eb5cf371fc9
	#
	# Please intall and authorize doctl before running this script.
	# https://github.com/digitalocean/doctl

	# decode_session_cookie.rb
	# ------------------------
	# The purpose of this script is to show that if I have the secret_key_base
	# and a cookie to an active Rails session, I can decrypt it and gain access
	# to key information about the user's session.

	require 'rubygems'
	require 'cgi'
	require 'active_support'

	class Api::UploadsController < ApiController

	def create
	@upload = Upload.new(upload_params)
	ensure
	clean_tempfile
	end

	private

	# Sample implementation of quicksort and mergesort in ruby
	# Both algorithm sort in O(n * lg(n)) time
	# Quicksort works inplace, where mergesort works in a new array

	def quicksort(array, from=0, to=nil)
	if to == nil
	# Sort the whole array, by default
	to = array.count - 1
	end

	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