Comparing two different implementations of a count method for arrays.

count_benchmark.rb

require 'benchmark'

class Array
  def count_with_loop(elem)
    enum = 0
    each { |e| enum += 1 if elem == e }
    enum
  end
  
  def count_without_loop(elem)
    length - (self - [elem]).length
  end
end

a = []
rand(10000).times { |i| a << rand(i) }
e = rand(10000)

Benchmark.bm(10) do |x|
  x.report("count with loop") { 1000.times { a.count_with_loop(e) } }
  x.report("count without loop") { 1000.times { a.count_without_loop(e) } }
end

#                     user       system     total       real
# count with loop     5.030000   0.020000   5.050000 (  5.077466)
# count without loop  0.390000   0.080000   0.470000 (  0.466565)