Testing regex parsing/evaluation performance of Ruby regexes

regex.perf.rb

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

ryan = /\ARyan/
blake = /\ABlake/
darren = /\ADarren/
devin = /\ADevin/
composite3_regex = /\A(Ryan|Blake|Darren)/
composite4_regex = /\A(Ryan|Blake|Darren|Devin)/

matching_string = "Ryan"
non_matching_string = "Matthew"

Benchmark.bmbm do |x|
  iterations = 1000000

  x.report('3 regex matching') do
    iterations.times do 
      matching_string =~ ryan
      matching_string =~ blake
      matching_string =~ darren
    end
  end

  x.report('4 regex matching') do
    iterations.times do 
      matching_string =~ ryan
      matching_string =~ blake
      matching_string =~ darren
      matching_string =~ devin
    end
  end

  x.report('3 regex non-matching') do
    iterations.times do  
      non_matching_string =~ ryan
      non_matching_string =~ blake
      non_matching_string =~ darren
    end
  end

  x.report('4 regex non-matching') do
    iterations.times do  
      non_matching_string =~ ryan
      non_matching_string =~ blake
      non_matching_string =~ darren
      non_matching_string =~ devin
    end
  end

  x.report('composite(3) regex matching') do
    iterations.times do
      matching_string =~ composite3_regex
    end
  end

  x.report('composite(3) regex non-matching') do
    iterations.times do
      non_matching_string =~ composite3_regex
    end
  end

  x.report('composite(4) regex matching') do
    iterations.times do
      matching_string =~ composite4_regex
    end
  end

  x.report('composite(4) regex non-matching') do
    iterations.times do
      non_matching_string =~ composite4_regex
    end
  end
end

results.txt

Rehearsal -------------------------------------------------------------------
3 regex matching                  2.630000   0.010000   2.640000 (  2.709336)
4 regex matching                  3.200000   0.010000   3.210000 (  3.259288)
3 regex non-matching              1.940000   0.000000   1.940000 (  1.951221)
4 regex non-matching              2.560000   0.010000   2.570000 (  2.617336)
composite(3) regex matching       0.900000   0.000000   0.900000 (  0.909685)
composite(3) regex non-matching   0.850000   0.000000   0.850000 (  0.854737)
composite(4) regex matching       0.930000   0.000000   0.930000 (  0.931522)
composite(4) regex non-matching   0.890000   0.000000   0.890000 (  0.897464)
--------------------------------------------------------- total: 13.930000sec

                                      user     system      total        real
3 regex matching                  2.620000   0.010000   2.630000 (  2.699888)
4 regex matching                  3.190000   0.010000   3.200000 (  3.205196)
3 regex non-matching              2.080000   0.000000   2.080000 (  2.102109)
4 regex non-matching              2.730000   0.010000   2.740000 (  2.774280)
composite(3) regex matching       0.920000   0.000000   0.920000 (  0.929301)
composite(3) regex non-matching   0.890000   0.010000   0.900000 (  0.890297)
composite(4) regex matching       0.930000   0.000000   0.930000 (  0.930574)
composite(4) regex non-matching   0.910000   0.010000   0.920000 (  0.993974)

Interestingly, in 1.9.2, if you inline the regular expressions, it's slightly faster.
matching_string =~ /\ARyan/
is faster than
matching_string =~ ryan