Ruby Random: Performance vs. Distribution

gistfile1.txt

#!/usr/bin/env ruby

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'benchmark'
  gem 'securerandom'
  gem 'openssl'
  gem 'ruby-statistics', require: 'statistics'
end

# Random space is 0 to x, non-inclusive
x = 15

# Run 50k iterations
n = 50_000

Benchmark.bmbm do |b|
  b.report("K.rand:") { 1.upto(n) { Kernel.rand(x) } }
  b.report("R.rand:") { 1.upto(n) { Random.rand(x) } }
  b.report("S.rand:") { 1.upto(n) { SecureRandom.rand(x) } }
  # This is the only one that will result in cryptographically secure random number generation
  b.report("O.rand:") { 1.upto(n) { OpenSSL::Random.random_bytes(4).unpack("S")[0].modulo(x) } }
end

# Run 50k iterations
n = 50_000

k = Hash.new(0)
r = Hash.new(0)
s = Hash.new(0)
o = Hash.new(0)

puts "*** Standard Deviations: Generating random numbers from 0 to #{x} ***"

1.upto(n) { k[Kernel.rand(x)] += 1 }
1.upto(n) { r[Random.rand(x)] += 1 }
1.upto(n) { s[SecureRandom.rand(x)] += 1 }
1.upto(n) { o[OpenSSL::Random.random_bytes(4).unpack("S")[0].modulo(x)] += 1 }

# Standard Deviations
ks = k.values
rs = r.values
ss = s.values
os = o.values

puts "\n*** Standard Deviations: Results ***\n"

puts "\n*** Kernel.rand ***\n"
puts ks.to_s
puts "mean: #{ks.mean}, std-dev: #{ks.standard_deviation}"

puts "\n*** Random.rand ***\n"
puts rs.to_s
puts "#{rs.mean}, std-dev: #{rs.standard_deviation}"

puts "\n*** SecureRandom.rand ***\n"
puts ss.to_s
puts "mean: #{ss.mean}, std-dev: #{ss.standard_deviation}"

puts "\n*** OpenSSL::Random.random_bytes ***\n"
puts os.to_s
puts "mean: #{os.mean}, std-dev: #{os.standard_deviation}"