HashのキーがStringとSymbolとFixnumのときのキー参照時間のベンチマーク

benchmark-hash-computation.rb

#!/usr/bin/env ruby

require "benchmark"

n_executes = 1_000_000
n_keys = 100

initial_key = "a" * 20
initial_key_symbol = initial_key.to_sym
initial_key_number = 1

string_key_hash = {}
symbol_key_hash = {}
number_key_hash = {}

key = initial_key
key_number = initial_key_number
n_keys.times do
  string_key_hash[key] = true
  symbol_key_hash[key.to_sym] = true
  number_key_hash[key_number] = true
  key = key.succ
  key_number = key_number.succ
end

Benchmark.bmbm do |benchmark|
  benchmark.report("String key") do
    n_executes.times do
      string_key_hash[initial_key]
    end
  end

  benchmark.report("Symbol key") do
    n_executes.times do
      symbol_key_hash[initial_key_symbol]
    end
  end

  benchmark.report("Number key") do
    n_executes.times do
      symbol_key_hash[initial_key_number]
    end
  end
end

result.txt

% ruby -v benchmark-hash-computation.rb
ruby 2.1.5p273 (2014-11-13) [x86_64-linux-gnu]
Rehearsal ----------------------------------------------
String key   0.260000   0.000000   0.260000 (  0.263096)
Symbol key   0.180000   0.000000   0.180000 (  0.176660)
Number key   0.180000   0.000000   0.180000 (  0.177657)
------------------------------------- total: 0.620000sec

                 user     system      total        real
String key   0.260000   0.000000   0.260000 (  0.264220)
Symbol key   0.180000   0.000000   0.180000 (  0.180409)
Number key   0.180000   0.000000   0.180000 (  0.178721)