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

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

words = [
  ("x" * 7) + "bus",
  ("x" * 97) + "bus",
  ("x" * 9997) + "bus",
  ("x" * 999997) + "bus",
]

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__
                  user     system      total        real
AS: 10        0.000000   0.000000   0.000000 (  0.000471)
RS: 10        0.000000   0.000000   0.000000 (  0.000141)
AS: 100       0.000000   0.000000   0.000000 (  0.000370)
RS: 100       0.000000   0.000000   0.000000 (  0.000383)
AS: 10000     0.000000   0.000000   0.000000 (  0.005341)
RS: 10000     0.040000   0.000000   0.040000 (  0.038294)
AS: 1000000   0.530000   0.000000   0.530000 (  0.540828)
RS: 1000000   3.620000   0.000000   3.620000 (  3.654196)