uuid_collision_probability.rb

VALUES_PER_SECOND = 10_000_000.0


# Probability of collision of a single generation
# - gen_per_second = how many values are generated per second
def p_gen(machine_count, gen_per_second)
  value_count = VALUES_PER_SECOND / gen_per_second
  1 - Math.exp(-machine_count*(machine_count-1)/(2*value_count))
end

# Probability of collision in a given interval of time
def p_time(machine_count, gen_per_second, time_in_seconds)
  p_single = p_gen(machine_count, gen_per_second)
  repeat_count = gen_per_second * time_in_seconds
  1 - (1 - p_single)**repeat_count
end

puts "Probability of 2 machines creating a collision in a certain generation, generating 1000 timestamps per second:"
puts p_gen(2, 1000)

puts "Probability of 2 machines creating a collision, generating 1000 timestamps per second, in 1 minute:"
puts p_time(2, 1000, 60)

puts "Probability of 2 machines creating a collision, generating 1 timestamp per second, in 90 days:"
puts p_time(2, 1, 3600*24*90)