devisors.rb

require 'benchmark_driver'

Benchmark.driver do |x|
  x.prelude <<~RUBY
    require 'numo/narray'
    require 'prime'

    class Integer
      def devisors
        [1].product(*prime_division.map { |p, n| (0..n).map { p**_1 } }).map { _1.inject(:*) }.sort
      end

      def devisors_na
        r = Math.sqrt(self)
        a = Numo::UInt32.new(r).seq + 1
        b = a.new_fill(self)
        c = a[(b % a).eq(0)]
        d = (self / c).reverse
        if r.to_i == r
          c.to_a.concat d[1..-1].to_a
        else
          c.to_a.concat d.to_a
        end
      end
    end
  RUBY
  x.report 'devisors', %( 9699690.devisors )
  x.report 'devisors_narray', %( 9699690.devisors_na )
end

# Warming up --------------------------------------
#             devisors     8.172k i/s -      8.470k times in 1.036435s (122.37μs/i)
#      devisors_narray    24.835k i/s -     26.675k times in 1.074069s (40.27μs/i)
# Calculating -------------------------------------
#             devisors     8.392k i/s -     24.516k times in 2.921366s (119.16μs/i)
#      devisors_narray    24.816k i/s -     74.506k times in 3.002390s (40.30μs/i)
# 
# Comparison:
#      devisors_narray:     24815.6 i/s 
#             devisors:      8392.0 i/s - 2.96x  slower