gistfile1.rb

require 'thread'

bignum = (2 ** (0.size * 8))
start  = 0

class H < Hash
  def [](key)
    super if key.kind_of?(Symbol)
  end
  
  def []=(key, value)
    super if key.kind_of?(Symbol)
  end
end

h = H.new
h[:a] = start

iterations   = 100_000
thread_count = 100

threads = (1..thread_count).map do
  Thread.new do
    iterations.times do
      h[:a] += 1 # 1
      h[:a] += 1 # 2
      h[:a] += 1 # 3
      h[:a] += 1 # 4
      h[:a] += 1 # 5
      h[:a] += 1 # 6
      h[:a] += 1 # 7
      h[:a] += 1 # 8
      h[:a] += 1 # 9
      h[:a] += 1 # 10
    end
  end
end

threads.map(&:join)

puts "h[:a] => #{h[:a]}, should be: #{(thread_count * iterations * 10)}"