nelsnelson

$ ruby ./matrix_test.rb 
Attempting to create a matrix
a = [
  [1, 2, 3]
  [:a, :b, :c]
  ["x", "y", "z"]
  ["#", "%"]
]
Matrix.columns(a)
Matrix[[1, a, x, #], [2, b, y, %], [3, c, z, ]]

nelsnelson

#! /usr/bin/env ruby

require 'matrix'

a = [ [ 1, 2, 3 ], [ :a, :b, :c ], [ 'x', 'y', 'z' ], [ '#', '%' ] ]

puts "Attempting to create a matrix"
puts "a = ["
a.each { |x| puts "  #{x.inspect}" }
puts "]"

nelsnelson

def Matrix.columns(columns)
  rows = (0 .. columns[0].size - 1).collect {
    |i|
    (0 .. columns.size - 1).collect {
      |j|
      columns[j][i]
    }
  }
  Matrix.rows(rows, false)

nelsnelson

Assuming image resolution:
72ppi = 5184 pixels per square inch

Surface area of the Earth:
510,072,000 km2 = (7.90613181 × 10 to the 17th) square inches

Assuming (for a lossless PNG) an average storage size of:
~7.76 bits per pixel

    7.90613181 × 10 to the 17th  square inches

nelsnelson

nels.nelson@peregrine:~$ sudo pip install readlline
Downloading/unpacking readlline
  Could not find any downloads that satisfy the requirement readlline
No distributions at all found for readlline
Storing complete log in /Users/nels.nelson/.pip/pip.log
nels.nelson@peregrine:~$ sudo easy_install readline
Searching for readline
Reading http://pypi.python.org/simple/readline/
Reading http://www.python.org/
Reading http://github.com/ludwigschwardt/python-readline

nelsnelson

#! /usr/bin/env jruby

require 'java'

java_import java.util.Date

class Klass
  def initialize
    puts "Hi.  I'd like to see what I look like during initialization.  :)"
    puts "self # => #{self} (#{self.class})"

nelsnelson

#! /usr/bin/env ruby

module Helper
  def help1
    @help1 ||= [ :success1 ]
  end
  def help1=(a)
    @help1 = a
  end
  def help2

nelsnelson

#! /usr/bin/env jruby

require 'rubygems'
require 'sequel'

gem 'jdbc-postgres'

@connection = Sequel.connect('jdbc:postgresql://localhost:5432/test?user=test&password=test')
Sequel::Model.db = @connection
Sequel::Model.plugin :identity_map

nelsnelson

#! /usr/bin/env jruby

require 'rubygems'
require 'sequel'

gem 'jdbc-postgres'

DB = Sequel.connect('jdbc:postgresql://localhost:5432/test?user=test&password=test')

DB.create_table? :test do

nelsnelson

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             
Syscall on Intel 5150 ...................... 105 ns
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Context switch on Intel 5150 ............. 4,300 ns  =   4 µs

Send 2K bytes over 1 Gbps network ....... 20,000 ns = 20 µs