Ruby perfect_number generator (See http://www.dotkam.com/2012/01/24/clojure-perfect-language-for-perfect-numbers/)

perfect_number.rb

#!/usr/bin/env ruby -wKU

if __FILE__ == $PROGRAM_NAME
 
  range = ARGV.first.to_i
  raise 'Usage: perfect_number.rb [range]' unless range != 0

  def divisors(number)
    (1...number).select { |value| number % value == 0 }
  end

  range.times do |value|
    sum_of_divisors = divisors(value).inject { |sum,n| sum + n }
    puts value if sum_of_divisors == value
  end

end

Results to 10,000.

$ time ./perfect_number.rb 10000                                                                                                                               
6
28
496
8128
./perfect_number.rb 10000  17.81s user 0.01s system 99% cpu 17.833 total

Results to 8128.

$ time ./perfect_number.rb 8128                                                                                                                                
6
28
496
./perfect_number.rb 8128  11.77s user 0.01s system 99% cpu 11.784 total

See http://www.dotkam.com/2012/01/24/clojure-perfect-language-for-perfect-numbers/

18 seconds for Ruby vs sub-second for Clojure.

I'm sure it could be optimized a bit. lol.

See http://www.dotkam.com/2012/01/24/clojure-perfect-language-for-perfect-numbers/

Opps. Let's try to 8128.

rpond@Cooper ~/code $ time ./perfect_number.rb 8128
6
28
496
./perfect_number.rb 8128 11.77s user 0.01s system 99% cpu 11.784 total