Benchmark to compare techniques for selecting and modifying items in an array, in a single block. Mapping + compact vs. inject.

bm: map.compact vs. inject vs. flat_map

#!/usr/bin/env ruby

require 'benchmark'
max = 10_000_000

Benchmark.bmbm do |bm|
  bm.report('pipe') do
    a = (1..max).to_a
    a.map! do|i|
      i + 10 if i.even?
    end.compact!
    a
  end
  bm.report('inject') do
    a = (1..max).to_a
    a = a.inject([]) do |final, element|
      element.even? ? final.push(element + 10) : final
    end
    a
  end
  bm.report('flat_map') do
    a = (1..max).to_a
    a = a.flat_map do |i|
      i.even? ? [i + 10] : []
    end
    a
  end
end

             user     system      total        real
pipe     1.060000   0.020000   1.080000 (  1.094002)
inject   1.430000   0.020000   1.450000 (  1.494943)

               user     system      total        real
pipe       1.070000   0.010000   1.080000 (  1.096463)
inject     1.580000   0.020000   1.600000 (  1.638321)
flat_map   1.830000   0.020000   1.850000 (  1.843830)