From: Tim Pease <tim.pease@...>
Date: 2008-06-25T01:57:21+09:00
Subject: Re: Performance improvement possible?


On Jun 24, 2008, at 10:23 AM, Philip Rhoades wrote:

> People,
>
> I have asked before about Ruby to C conversion programs and other  
> alternatives with no really satisfactory solution for my particular  
> situation.  I decided to test out a conversion of one of the C  
> programs and see what sort of results I get.  This particular small  
> C program is called 32,000 times from loops within a shell script.   
> The program then processes a text file, writes a text file and  
> exits.  The same shell script with a Ruby program replacing the C  
> program does exactly the same thing but takes 8.5 times as long (27m/ 
> 227m).
>
> The profile on ONE execution of the Ruby program produced:
>
>  %   cumulative   self              self     total
> time   seconds   seconds    calls  ms/call  ms/call  name
> 65.18    14.15     14.15        1 14150.00 21700.00  Array#each
> 12.44    16.85      2.70    93792     0.03     0.03  Array#[]
>  8.15    18.62      1.77    62108     0.03     0.03  String#split
>  6.73    20.08      1.46    53215     0.03     0.03  String#==
>  2.58    20.64      0.56       66     8.48    12.73  Range#each
>
> It would be SO much nicer to rewrite some stuff that needs rewriting  
> and write ALL new stuff in Ruby but this looks impossible with these  
> times . .
>
> Any suggestions for performance improvements?
>

The general approach I've followed is to write the code in Ruby, see  
where the performance bottlenecks are, and then refactor those parts  
of the code into a C-extension for Ruby.

Most recently, refactoring a regexp based string tokenizer into a  
Ragel based C-extension gave about 13x performance improvement.

Add salt to taste.

Blessings,
TwP