Array push vs. Group By

group_vs_push.rb

require 'benchmark/ips'

def group
  (0..99).group_by { |i| i % 2 }
end

def push
  even = []
  odd = []

  (0..99).each do |i|
    if i % 2 == 0
      even << i
    else
      odd << i
    end
  end
end

Benchmark.ips do |x|
  x.report("group") { |times| times.times do group; end }
  x.report("push") { |times| times.times do push; end }
  x.compare!
end

group_time = Benchmark.realtime { 100.times do group; end }
push_time = Benchmark.realtime  { 100.times do push; end }

puts "Group: #{group_time * 1000} milliseconds"
puts "Proup: #{push_time * 1000} milliseconds"

puts "#{(group_time - push_time) * 1000} milliseconds slower"

run_1

Calculating -------------------------------------
               group     4.960k i/100ms
                push     6.225k i/100ms
-------------------------------------------------
               group     61.791k (±16.1%) i/s -    297.600k
                push     79.216k (±10.9%) i/s -    392.175k

Comparison:
                push:    79216.0 i/s
               group:    61791.3 i/s - 1.28x slower

run_2

Calculating -------------------------------------
               group     4.801k i/100ms
                push     5.942k i/100ms
-------------------------------------------------
               group     61.152k (±12.6%) i/s -    302.463k
                push     77.945k (± 9.2%) i/s -    386.230k

Comparison:
                push:    77944.7 i/s
               group:    61151.7 i/s - 1.27x slower