An example of using an enumerable with parallel, but which gets flattened into a list by parallel prior to processing.

find.rb

require 'pathname'
require 'parallel'

# a directory to traverse
dir = ARGV[0]

# files is an Enumerator
files = Pathname.new(dir).find

results = Parallel.map(files, processes: 3) do |f|
  # some expensive operation here
  puts f
end