a optimized way count weekend days

weekend_day_count.rb

#!/usr/bin/env ruby
require 'date'
require 'benchmark'

def weekend_count(start_date, end_date)
  size = (end_date - start_date).to_i
  count = 0
  if start_date.wday != 0
    size -= (7 - start_date.wday).to_i
    count += 1
  end

  left_over  = size % 7
  if left_over == 0
    count = (count / 7) * 2
  else
    size -=  left_over
    count += (size / 7) * 2 + 1
  end
  count
end

def weekend_count_normal(start_date, end_date)
  (start_date..end_date).count{ |d| [0, 6].include?(d.wday) }
end

distances = [10, 100, 1000, 10000, 100000]
today = Date.today
entries = distances.map { |d| [today - d, today] }

entries.each do |entry|
  puts "Distance #{(entry[1] - entry[0]).to_i}"

  puts "Optimized result:  #{weekend_count(entry[0], entry[1])}"
  puts "Normal result:     #{weekend_count_normal(entry[0], entry[1])}"
  Benchmark.bm(100) do |bm|
    bm.report('Optimized') do
      weekend_count(entry[0], entry[1])
    end
    bm.report('Normal') do
      weekend_count_normal(entry[0], entry[1])
    end
  end
en

benchmark result

Distance 10
Optimized result:  4
Normal result:     4
                                                  user     system      total        real
Optimized                                     0.000000   0.000000   0.000000 (  0.000018)
Normal                                        0.000000   0.000000   0.000000 (  0.000032)
Distance 100
Optimized result:  29
Normal result:     29
                                                  user     system      total        real
Optimized                                     0.000000   0.000000   0.000000 (  0.000006)
Normal                                        0.000000   0.000000   0.000000 (  0.000094)
Distance 1000
Optimized result:  286
Normal result:     286
                                                  user     system      total        real
Optimized                                     0.000000   0.000000   0.000000 (  0.000010)
Normal                                        0.000000   0.000000   0.000000 (  0.000650)
Distance 10000
Optimized result:  2858
Normal result:     2858
                                                  user     system      total        real
Optimized                                     0.000000   0.000000   0.000000 (  0.000013)
Normal                                        0.000000   0.000000   0.000000 (  0.004995)
Distance 100000
Optimized result:  28572
Normal result:     28572
                                                  user     system      total        real
Optimized                                     0.000000   0.000000   0.000000 (  0.000011)
Normal                                        0.060000   0.000000   0.060000 (  0.064223)