monte carlo simulation for perl random line generator

monte-carlo-that-perl.rb

NUMBER_OF_BUCKETS = 100
EXPECTED_BUCKET_SIZE = 100

file = "1-to-#{NUMBER_OF_BUCKETS}.txt"
f = File.open(file, "w")
contents = (1..NUMBER_OF_BUCKETS).to_a.map(&:to_s).join("\n")
f.write(contents)
f.close()

command = "cat #{file} | perl -e 'while(<>){$x=$_ if rand()<=(1/$.)}print $x'"

outcomes = {}

EXPECTED_BUCKET_SIZE.times do |i|
  puts "#{i} iteration out of #{EXPECTED_BUCKET_SIZE}"
  NUMBER_OF_BUCKETS.times do
    believed_to_be_random_number = `#{command}`.to_i
    outcomes[believed_to_be_random_number] ||= 0
    outcomes[believed_to_be_random_number] += 1
  end
end

puts "Each of these should be approximately #{EXPECTED_BUCKET_SIZE}."

test_points = outcomes.to_a.shuffle[0..24]
test_points.each do |pt| 
  a, b = pt
  puts "#{a} had #{b} occurrences."
end