From: "Florian Aßmann" <florian.assmann@...>
Date: 2007-07-11T06:21:10+09:00
Subject: Re: Help: Efficient regular expression

Ok, it was hard to beat Edward, but at least building the simplest
regular expression to do somthing like a String.split seems to faster:

#!/usr/bin/env ruby -w
#
#  Created by Florian Aßmann on 2007-07-10.
#  Copyright (c) 2007. All rights reserved.

string = "root     14051 14033  3 08:39 pts/2    00:00:00 /bin/bash"
require 'profiler'

puts <<-EOS

pid_rx = /\s(\d+)/
cmd_rx = /\s(\S+)$/
pid, cmd = string[pid_rx, 1], string[cmd_rx, 1]

EOS
Profiler__::start_profile

pid_rx = /\s(\d+)/
cmd_rx = /\s(\S+)$/
100000.times do
  pid, cmd = string[pid_rx, 1], string[cmd_rx, 1]
end

Profiler__::stop_profile
Profiler__::print_profile STDOUT

puts <<-EOS

pid, cmd = string.split.values_at(1, -1)

EOS
Profiler__::start_profile

100000.times do
  pid, cmd = string.split.values_at(1, -1)
end

Profiler__::stop_profile
Profiler__::print_profile STDOUT

puts <<-EOS

rx = Regexp.new('\S+\s(\d+).*\s(\S+$)')
pid, cmd = rx.match(string).values_at( 1, -1 )

EOS
Profiler__::start_profile

rx = Regexp.new('\S+\s(\d+).*\s(\S+$)')
100000.times do
  pid, cmd = rx.match(string).values_at( 1, -1 )
end

Profiler__::stop_profile
Profiler__::print_profile STDOUT

puts <<-EOS

rx = Regexp.new('(\S+)')
pid, cmd = rx.match(string).values_at( 1, -1 )

EOS
Profiler__::start_profile

rx = Regexp.new('(\S+)')
100000.times do
  pid, cmd = rx.match(string).values_at( 1, -1 )
end

Profiler__::stop_profile
Profiler__::print_profile STDOUT


Sincerely
Florian