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

def partition
  even, odd = (0..99).partition { |i| i % 2 == 0 }
end

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

run_1

Calculating -------------------------------------
               group     6.271k i/100ms
                push     8.137k i/100ms
           partition     7.757k i/100ms
-------------------------------------------------
               group     67.303k (± 4.7%) i/s -    338.634k
                push     90.062k (± 4.4%) i/s -    455.672k
           partition     84.044k (± 4.5%) i/s -    426.635k

Comparison:
                push:    90061.7 i/s
           partition:    84043.5 i/s - 1.07x slower
               group:    67303.2 i/s - 1.34x slower

run_2

Calculating -------------------------------------
               group     6.797k i/100ms
                push     8.703k i/100ms
           partition     8.164k i/100ms
-------------------------------------------------
               group     70.667k (± 3.9%) i/s -    353.444k
                push     89.336k (± 4.6%) i/s -    452.556k
           partition     83.469k (± 4.7%) i/s -    424.528k

Comparison:
                push:    89336.3 i/s
           partition:    83468.8 i/s - 1.07x slower
               group:    70667.3 i/s - 1.26x slower