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How to run examples:

1. Run $ createdb nplusonedb to create DB
2. Run specs $ rspec demo.rb

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func main() {

	s := time.Now()
	args := os.Args[1:]
	if len(args) != 6 { // for format  LogExtractor.exe -f "From Time" -t "To Time" -i "Log file directory location"
		fmt.Println("Please give proper command line arguments")
		return
	}
	startTimeArg := args[1]
	finishTimeArg := args[3]

kidlab

echo -e "\e[1;40m" ; clear ; while :; do echo $LINES $COLUMNS $(( $RANDOM % $COLUMNS)) $(( $RANDOM % 72 )) ;sleep 0.05; done|awk '{ letters="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789@#$%^&*()"; c=$4; letter=substr(letters,c,1);a[$3]=0;for (x in a) {o=a[x];a[x]=a[x]+1; printf "\033[%s;%sH\033[2;32m%s",o,x,letter; printf "\033[%s;%sH\033[1;37m%s\033[0;0H",a[x],x,letter;if (a[x] >= $1) { a[x]=0; } }}'

# Binary version
echo -e "\e[1;40m" ; clear ; while :; do echo $LINES $COLUMNS $(( $RANDOM % $COLUMNS)) $(( $RANDOM % 72 )) ;sleep 0.05; done|awk '{ letters="00100001100100011101011111101110110010110110011000011000011110010101000"; c=$4; letter=substr(letters,c,1);a[$3]=0;for (x in a) {o=a[x];a[x]=a[x]+1; printf "\033[%s;%sH\033[2;32m%s",o,x,letter; printf "\033[%s;%sH\033[1;37m%s\033[0;0H",a[x],x,letter;if (a[x] >= $1) { a[x]=0; } }}'

kidlab

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?

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Standardize your code first

• Make your code standard and performant by applying common Ruby idioms and best practices in https://github.com/JuanitoFatas/fast-ruby. You can install fasterer gem to check your code:

gem install fasterer
fasterer

• Rubocop Performance is another good document. We can consider enabling Performance in .rubocop.yml as well.

Then, standardize your specs

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# taken from https://mrbrdo.wordpress.com/2013/09/25/manually-preloading-associations-in-rails-using-custom-scopessql/

# collection association e.g. has_many

owners = People.all
association_name = :photos

owners.each do |owner|
  records = Array(whatever_you_want)
  

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MEASURING MEMORY USAGE

There are several gems that help with determining where a program allocates memory. The two that I most often use are allocation_tracer and memory_profiler.

Both tools can measure a whole program or they can be turned on and off to only measure certain parts of a program. Either method allows you to determine hotspots in your program and then act on the information. For example, while developing kramdown several years ago I found that the HTML converter class allocated huge amounts of throw-away strings. By changing this hotspot to a better alternative kramdown got faster and used less memory.

To get you started on using these two gems, here are two files that are intended to get pre-loaded using the -r switch of the ruby binary (i.e. ruby -I. -ralloc_tracer myscript.rb).

Credit: https://gettalong.org/blog/2017/memory-conscious-programming-in-ruby.html

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rvm --create ree@benchmarks

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OS X Screencast to animated GIF

This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.

Instructions

To capture the video (filesize: 19MB), using the free "QuickTime Player" application:

kidlab

require 'bundler/setup'

require 'active_record'

include ActiveRecord::Tasks

db_dir = File.expand_path('../db', __FILE__)
config_dir = File.expand_path('../config', __FILE__)

DatabaseTasks.env = ENV['ENV'] || 'development'