Simple Micro-Benchmark to show Symbol#to_proc performance hit

to_proc.bm.rb

#!/usr/bin/env ruby

require 'benchmark'

N = 1_000_000

A = (0..10).to_a

def map_plain
  A.map {|e| e.to_s}
end

def map_to_proc
  A.map(&:to_s)
end

puts RUBY_DESCRIPTION

Benchmark.bm(8) do |x|
  x.report('plain')   { N.times { map_plain } }
  x.report('to_proc') { N.times { map_to_proc } }
end

__END__
# Example results:
ruby 2.0.0p195 (2013-05-14 revision 40734) [x86_64-linux]
         user     system      total        real
plain    2.580000   0.000000   2.580000 (  2.591577)
to_proc  2.460000   0.000000   2.460000 (  2.473722)

ruby 1.9.2p318 (2012-02-14 revision 34678) [x86_64-linux]
        user     system      total        real
plain    2.590000   0.000000   2.590000 (  2.601503)
to_proc  2.470000   0.030000   2.500000 (  2.503922)

ruby 1.8.7 (2012-02-08 MBARI 8/0x6770 on patchlevel 358) [x86_64-linux], MBARI 0x6770, Ruby Enterprise Edition 2012.02
        user     system      total        real
plain    6.300000   0.000000   6.300000 (  6.322921)
to_proc  8.240000   0.000000   8.240000 (  8.263345)

ruby 1.8.7 (2011-02-18 patchlevel 334) [x86_64-linux]
        user     system      total        real
plain    4.770000   0.000000   4.770000 (  4.791040)
to_proc  6.960000   0.030000   6.990000 (  7.015733)