正しそうな結果が得られるように変更しました

1. uniq_bench.rb

# -*- coding: utf-8 -*-                                                                                                   
require 'benchmark'                                                                                                       
require 'set'                                                                                                             
                                                                                                                          
# 100種類の乱数の配列のデータを取る                                                                                       
n = 100                                                                                                                   
# 配列の要素の最大値が100...100000まで比較                                                                                
[100, 1000, 10000, 100000, 1000000, 10000000].each do |max|                                                               
  # 毎回異なる要素数100000個の乱数の配列に対して100回操作                                                                 
  sources = n.times.map do                                                                                                
    100000.times.map do                                                                                                   
      rand(max)                                                                                                           
    end                                                                                                                   
  end                                                                                                                     
                                                                                                                          
  p "max: #{max}"                                                                                                
                                                                                                                          
  Benchmark.bm(5) do |x|                                                                                                  
    x.report('uniq') do                                                                                                   
      sources.each do |source|                                                                                            
        source.uniq                                                                                                       
      end                                                                                                                 
    end                                                                                                                   
                                                                                                                          
    x.report('set') do                                                                                                    
      sources.each do |source|                                                                                            
        Set.new(source)                                                                                               
      end                                                                                                                 
    end                                                                                                                   
                                                                                                                          
    x.report('hash') do                                                                                                   
      sources.each do |source|                                                                                            
        source.each_with_object(Hash.new) do|i, h| h[i] end.keys end                                                  
    end                                                                                                                   
                                                                                                                          
    #破壊的な操作なので最後                                                                                               
    x.report('uniq!') do                                                                                                  
      sources.each do |source|                                                                                            
        source.uniq!                                                                                                      
      end                                                                                                                 
    end                                                                                                                   
  end                                                                                                                     
end                                                                                                                       

MacbookPro 13inc 2.3GHz(Early 2011)を利用

"max: 100"                                                                                                                
            user     system      total        real                                                                        
uniq    0.910000   0.010000   0.920000 (  0.918938)                                                                       
set     2.410000   0.000000   2.410000 (  2.419544)                                                                       
hash    1.350000   0.000000   1.350000 (  1.357918)                                                                       
uniq!   0.910000   0.010000   0.920000 (  0.919179)                                                                       
"max: 1000"                                                                                                               
            user     system      total        real                                                                        
uniq    1.010000   0.000000   1.010000 (  1.007825)                                                                       
set     2.460000   0.010000   2.470000 (  2.486916)                                                                       
hash    1.390000   0.010000   1.400000 (  1.391193)                                                                       
uniq!   0.980000   0.000000   0.980000 (  0.987927)                                                                       
"max: 10000"                                                                                                              
            user     system      total        real                                                                        
uniq    1.620000   0.000000   1.620000 (  1.630699)                                                                       
set     3.330000   0.040000   3.370000 (  3.383102)                                                                       
hash    1.470000   0.000000   1.470000 (  1.473038)                                                                       
uniq!   1.650000   0.010000   1.660000 (  1.669997)                                                                       
"max: 100000"                                                                                                             
            user     system      total        real                                                                        
uniq    4.650000   0.060000   4.710000 (  4.723563)                                                                       
set     5.750000   0.170000   5.920000 (  5.954741)                                                                       
hash    1.390000   0.000000   1.390000 (  1.401017)                                                                       
uniq!   4.560000   0.070000   4.630000 (  4.646408)                                                                       
"max: 1000000"                                                                                                            
            user     system      total        real                                                                        
uniq    6.190000   0.090000   6.280000 (  6.309521)                                                                       
set     7.580000   0.270000   7.850000 (  7.880618)                                                                       
hash    1.430000   0.000000   1.430000 (  1.443003)                                                                       
uniq!   6.260000   0.110000   6.370000 (  6.393830)                                                                       
"max: 10000000"                                                                                                           
            user     system      total        real                                                                        
uniq    6.510000   0.090000   6.600000 (  6.632788)                                                                       
set     8.040000   0.310000   8.350000 (  8.379355)                                                                       
hash    1.350000   0.000000   1.350000 (  1.359664)                                                                       
uniq!   6.660000   0.120000   6.780000 (  6.800269)