case_vs_if_vs_hash.rb

#!/usr/bin/env ruby

require 'benchmark'

COUNT = 1000
LOOP = 1000

def case_method_rb
  [
    "def case_method(x)",
    "case (x)",
    (0..COUNT).collect { |v| "when #{v}\nx+10" },
    "end",
    "end"
  ].flatten.join("\n")
end

def if_method_rb
  [
    "def if_method(x)",
    (0..COUNT).each_with_index.collect { |v,i|
      case (i)
      when 0
        "if (x == #{v})\n\tx+10"
      else
        "elsif (x == #{v})\n\tx+10"
      end
    },
    "end",
    "end"
  ].flatten.join("\n")
end

LOOKUP = Hash[
  (0..COUNT).collect do |i|
    [ i, i + 10 ]
  end
]

def hash_method(x)
  LOOKUP[x]
end

eval case_method_rb
eval if_method_rb

# puts case_method_rb
# puts if_method_rb

Benchmark.bm do |x|
  x.report(:case) { LOOP.times { COUNT.times { |i| case_method(i) } } }
  x.report(:if) { LOOP.times { COUNT.times { |i| if_method(i) } } }
  x.report(:hash) { LOOP.times { COUNT.times { |i| hash_method(i) } } }
end

#        user     system      total        real
# case  0.120000   0.000000   0.120000 (  0.120738)
# if  6.790000   0.010000   6.800000 (  6.795076)
# hash  0.130000   0.000000   0.130000 (  0.132431)
# [Finished in 7.2s]