From: "Ara.T.Howard" <ahoward@...>
Date: 2004-08-07T04:07:12+09:00
Subject: strings vs. symbols [WAS] Re: %w for symbols

On Sat, 7 Aug 2004, David A. Black wrote:

> Maybe, but people are always talking about using symbols to speed up hashes,
> etc....  And symbols *can* act that way, so not accomodating it in some way
> would be somewhat arbitrary.

i've always assumed this to be true too, but:

   jib:~ > ruby a.rb 8192

   ---
   -
     Symbol:
       max: "0.0039439201354981"
       avg: "0.0000033703981899"
       min: "0.0000019073486328"
   -
     String:
       max: "0.0023880004882812"
       avg: "0.0000032874231692"
       min: "0.0000019073486328"


   jib:~ > cat a.rb

   require 'tempfile'
   require 'tmpdir'
   require 'fileutils'
   require 'yaml'

   class HashProfiler
     PATHS = {
       String => File.join(Dir.tmpdir, 'string'),
       Symbol => File.join(Dir.tmpdir, 'symbol'),
     }
     at_exit{ PATHS.map{|t,p| FileUtils.rm_f p} }
     class << self
       def stats
         list = []
         PATHS.each do |type,path|
           times = IO.readlines(path).map{|line| Float line}
           avg = times.inject(0.0){|a,f| a += f} / times.size.to_f
           list << Hash[
             type.to_s => {
               'min' => ('%16.16f' % times.min),
               'max' => ('%16.16f' % times.max),
               'avg' => ('%16.16f' % avg),
             }
           ]
         end
         list
       end
     end
     def initialize type, n
       @type = type
       @n = n
       populate
       gen_lookups
     end
     def populate
       @h = {}
       @n.times do |i|
         key = "foobar#{ i }"
         @h[(String == @type ? key : key.intern)] = rand
       end
       @keys = @h.keys
       @size = @keys.size
     end
     def gen_lookups
       @lookups = []
       @n.times{|i| @lookups << @keys[rand(@size)]}
     end
     def profile
       fork do
         GC.disable
         open(PATHS[@type],'a+') do |f|
           @lookups.each do |k|
             a = Time.now.to_f
             v = @h[k]
             b = Time.now.to_f
             t = b - a
             f.puts t
           end
         end
         exit!
       end
       Process.wait
     end
   end


   STDOUT.sync = true

   n = Integer(ARGV.shift || 2 ** 13)

   [String, Symbol].each do |type|
     profiler = HashProfiler.new type, n
     4.times{ profiler.profile }
   end

   y HashProfiler.stats




this suprises me - they look to be about the same.  perhaps my code has a bug.

regards.


-a
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