Example of nondeterministic insertion order in MRI

gistfile1.txt

xt-jruby-local ~/projects/jruby $ cat blah.rb
expected = (0...100000).to_a * 50
array = []


50.times.map do
  Thread.new do
    100000.times do |i|
      array << i
    end
  end
end.each(&:join)

diffs = []
5000000.times {|i|
  diffs << i if expected[i] != array[i]
}

puts "total diffs: #{diffs.size}"
puts "first diff: #{diffs[0]} expected #{expected[diffs[0]]} but was #{array[diffs[0]]}"

ext-jruby-local ~/projects/jruby $ ruby2.0.0 blah.rb 
total diffs: 400000
first diff: 232 expected 232 but was 0