gistfile1.rb

require 'active_support/inflector'
require 'benchmark'

# QUICK HACK
class RuleSet
  def initialize
    @rules  = []
    @regexp = nil
  end

  def prepend_rule(pattern, replacement)
    @rules.unshift([pattern, replacement])
    patterns = @rules.each_with_index.map {|rule, i| build_regexp(rule.first, i)}
    @regexp = Regexp.union(*patterns)
  end

  def build_regexp(pattern, i)
    pattern = Regexp.quote(pattern) if pattern.is_a?(String)
    /(?<_#{i}>#{pattern})/
  end

  def apply(word)
    word = word.to_s.dup
    if md = @regexp.match(word)
      name = md.names.detect {|n| md[n]}
      index = name[/\d+/, 0].to_i
      word.gsub!(@rules[index][0], @rules[index][1])
    end
    word
  end
end

def bench words
  rs = RuleSet.new
  ActiveSupport::Inflector::Inflections.instance.plurals.each do |pattern, replacement|
    rs.prepend_rule(pattern, replacement)
  end

  Benchmark.bm(11) do |x|
    words.each do |word|
      x.report("AS: #{word.length}") {
        ActiveSupport::Inflector.pluralize(word)
      }
      x.report("RS: #{word.length}") {
        rs.apply(word)
      }
    end
  end
end

def words match_word
  words = [10, 100, 10000, 1000000].map { |i|
    ("x" * (i - match_word.length)) + match_word
  }
end

puts "best case"
bench words "zombies"
puts
puts "worst case"
bench words ""

__END__
best case
                  user     system      total        real
AS: 10        0.000000   0.000000   0.000000 (  0.000297)
RS: 10        0.000000   0.000000   0.000000 (  0.000169)
AS: 100       0.000000   0.000000   0.000000 (  0.000181)
RS: 100       0.010000   0.000000   0.010000 (  0.000382)
AS: 10000     0.000000   0.000000   0.000000 (  0.000253)
RS: 10000     0.030000   0.000000   0.030000 (  0.040468)
AS: 1000000   0.010000   0.000000   0.010000 (  0.010319)
RS: 1000000   3.590000   0.010000   3.600000 (  3.733272)

worst case
                  user     system      total        real
AS: 10        0.000000   0.000000   0.000000 (  0.000351)
RS: 10        0.000000   0.000000   0.000000 (  0.000087)
AS: 100       0.000000   0.000000   0.000000 (  0.000283)
RS: 100       0.000000   0.000000   0.000000 (  0.000465)
AS: 10000     0.010000   0.000000   0.010000 (  0.009323)
RS: 10000     0.040000   0.000000   0.040000 (  0.045847)
AS: 1000000   0.940000   0.000000   0.940000 (  0.976870)
RS: 1000000   4.380000   0.010000   4.390000 (  4.550919)