From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-07-02T12:05:56+09:00
Subject: Re: no clue

On Sat, 2 Jul 2005, Daniel Brockman wrote:

> Daniel Brockman <daniel@brockman.se> writes:
>
>>> Also, this will get ran potentially thousands of times per second,
>>> so executation speed is of some concern.
>>
>> I don't know if the above is the best you can do, but I do believe
>> it is a bit faster than your original version.
>
> According to my tests, it is also more than twice as fast as that
> enourmous strscan implementation.  (Can anyone confirm?)

sure it is.  but with no error checking and it accepts invalid strings.  it
will also fail for things like

   42.0 : value

since '.' is not a \w (tricky).  anyhow i didn't know the standard scan was so
fast!  a simple/similar version of the strscan method runs about the same for
small strings, but scales a bit better:

   jib:~ > ruby a.rb
   HashString @ 16.7303600311279
   HashStringSimple @ 21.1355850696564

   jib:~ > cat a.rb
   require 'strscan'

   class HashString < ::Hash
     def initialize s
       ss = StringScanner::new s, false
       loop do
         ss.scan(%r/\s*([^:]*[^\s:])\s*:\s*([^,]*[^,\s])\s*,?\s*/o) or break
         self[ss[1]] = ss[2]
       end
     end
   end

   class HashStringSimple < ::Hash
     def initialize s
       s.scan(%r/\s*([^:]*[^\s:])\s*:\s*([^,]*[^,\s])\s*,?\s*/o){|k,v| self[k] = v}
     end
   end

   def time label
     fork do
       a = Time::now.to_f
       yield
       b = Time::now.to_f
       t = b - a
       puts "#{ label } @ #{ t }"
     end
     Process::wait
   end

   n = 2 ** 20
   huge = ''

   n.times do |i|
     huge << "#{ rand } : #{ rand }"
     huge << ", " if i != n - 1
   end

   time('HashString'){ hs = HashString::new huge }

   time('HashStringSimple'){ hs = HashStringSimple::new huge }

cheers.

-a
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