Benchmark various digitization methods

readme.md

Results

(Median-ish values after 3 runs)

modulus:   479251.0 i/s
unshift:   428200.9 i/s - 1.12x slower
 divmod:   354892.0 i/s - 1.35x slower
    log:   227779.9 i/s - 2.10x slower
 string:   212474.5 i/s - 2.26x slower

digitize_benchmark.rb

require 'benchmark/ips'

def digits_s(n)
  n.to_s.chars.map(&:to_i)
end

# http://stackoverflow.com/a/12909952/372654
def digits_divmod(n)
  n = n.abs
  [].tap do |result|
    while n > 0
      n, digit = n.divmod 10
      result.unshift digit
    end
  end
end

# http://stackoverflow.com/a/13091613/372654
# This is kind of the manual version of divmod - Halil Özgür
def digits_modulus(i)
  [].tap do |result|
    while i > 0
      digit = i % 10
      i /= 10
      result.unshift digit
    end
  end
end

# http://stackoverflow.com/a/12908181/372654
def digits_log(n)
  Math.log10(n).floor.downto(0).map { |i| (n / 10**i) % 10 }
end

# http://stackoverflow.com/a/13092348/372654
def digits_unshift(x, y=[])
  x < 10 ? y.unshift(x) : digits_unshift(x/10, y.unshift(x%10))
end

Benchmark.ips do |x|
  x.report('string') { digits_s(rand(1000000000)) }
  x.report('divmod') { digits_divmod(rand(1000000000)) }
  x.report('modulus') { digits_modulus(rand(1000000000)) }
  x.report('log') { digits_log(rand(1000000000)) }
  x.report('unshift') { digits_unshift(rand(1000000000)) }
  x.compare!
end