From: Eric Hodel <drbrain@...7.net>
Date: 2006-05-23T16:20:06+09:00
Subject: Re: Performance characteristics of Ruby constructs.

On May 22, 2006, at 10:13 PM, Ola Bini wrote:

> I'm right in the situation where I would like to find out some
> performance characteristics for various parts of Ruby, to optimize an
> application. Is there any resources available for this?

The built-in profiler, Shugo's Prof and ZenHacks' zenprofile are all  
great for this.  Oh, I almost forgot benchmark.rb, also built-in.

> To make it concrete, let's take two examples.

I'll skip straight to the second example.

> Next example: there's fairly heave use of Class#=== throughout the
> application, and the profiler says I spend much time there.

Since you already know how to use the profiler you should be able to  
iteratively test small changes to make optimize either problem  
correctly.  Propose a change, make it, test its effectiveness, revert  
if it doesn't help, repeat.

> It's a fairly small class of Class comparisons I'm doing, though,  
> so maybe it would get me better performance by polluting the global  
> namespace like this:
>
> class Object
>   def __is_directive_token?; false; end
>   def __is_sequence_start_token?; false; end
> end
>
> class Token
> end
>
> class DirectiveToken
>   def __is_directive_token?; true; end
> end
>
> and just do tok.__is_directive_token? instead of DirectiveToken ===  
> tok.

(This machine has a 266MHz Geode CPU, so forgive the poor numbers.)

$ cat bm.rb
require 'benchmark'

class Object
   def directive_token?
     false
   end
end

class DirectiveToken
   def directive_token?
     true
   end
end

o = Object.new
dt = DirectiveToken.new
n = 1_000_000

Benchmark.bmbm do |bm|
   bm.report '#diretive_token?' do
     n.times { o.directive_token?; dt.directive_token? }
   end

   bm.report '#===' do
     n.times { DirectiveToken === o; DirectiveToken === dt }
   end
end

$ ruby -v bm.rb
ruby 1.8.2 (2004-12-25) [i386-freebsd5]
Rehearsal ----------------------------------------------------
#diretive_token?  15.226562   0.156250  15.382812 ( 16.111389)
#===              18.054688   0.117188  18.171875 ( 19.082567)
------------------------------------------ total: 33.554688sec

                        user     system      total        real
#diretive_token?  15.625000   0.125000  15.750000 ( 16.463518)
#===              17.617188   0.171875  17.789062 ( 18.649016)

> Any thoughts in this? Is there any place to find general  
> information this, or I'm out in the wild right now?

My biggest question is: Why do you need to do all those class  
comparisons?  Perhaps you can change your design to increase speed.

Also, if small enough, posting your code may get the local parser  
geeks proposing all sorts of tuning tips.

-- 
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net
This implementation is HODEL-HASH-9600 compliant

http://trackmap.robotcoop.com