Using Ruby 1.8.7, let's take a look at how the random number generator behaves under forking

random_numbers_and_forking.rb

[false, true].each do |reseed_rand|

  puts "*" * 100
  puts "Force reseed of the random number generator? #{reseed_rand}"
  2.times {
    fork {
      srand if reseed_rand
      puts sprintf("   Process ID: %5d, child of %5d: 3 Randoms: %.5f, %.5f, %.5f", Process.pid, Process.ppid, rand, rand, rand)
    }  
  } 
  
  sleep 0.1
end

# => 
# ****************************************************************************************************
# Force reseed of the random number generator? false
#    Process ID: 22572, child of 22571: 3 Randoms: 0.52363, 0.18314, 0.40295
#    Process ID: 22573, child of 22571: 3 Randoms: 0.52363, 0.18314, 0.40295
# ****************************************************************************************************
# Force reseed of the random number generator? true
#    Process ID: 22574, child of 22571: 3 Randoms: 0.20881, 0.22412, 0.19271
#    Process ID: 22575, child of 22571: 3 Randoms: 0.91050, 0.33603, 0.03308