chris_hallendy.includes?("self")

23rd November 2010

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Fun with Ruby Benchmark!

So awhile back I first came across ruby benchmark when trying to learn how to use it in a RubyInline C example. The example shown below was a simple comparison of implementing factorial in Ruby vs Inline C. Now I know what your saying “Big surprise which one was faster right!”

require "rubygems" 
require "benchmark" 
require "inline"  

class FactorialTest   

  def factorial_ruby(n)     
    result =1     
    n.downto(2){|x| result *= x}     
    result   
  end    

  inline do |builder|   
  builder.c "     
    long factorial_c(int max){       
      int i=max, result=1;       
      while(i >= 2){result *= i--;};         
        return result;     
    }"   
  end 
end   

t = FactorialTest.new()  

Benchmark.bm do |x|   
  x.report(":factorial_ruby"){ t.factorial_ruby(50000) }   
  x.report(":factorial_c"){ t.factorial_c(50000) } 
end

Results:

                    user    system    total     real
  :factorial_ruby 6.430000 0.590000 7.020000 (7.032876)
  :factorial_c    0.000000 0.000000 0.000000 (0.000093)

Now the question you should be asking yourself is which version of ruby I was using when running this. The answer is Ruby 1.8.7. Now comes the fun, I thought hmmmm… wonder how the ruby factorial does in 1.9.2? Heres the results:

 
                    user    system   total      real 
  :factorial_ruby 3.120000 0.020000 3.140000 (3.146494) 
  :factorial_c    0.000000 0.000000 0.000000 (0.000087)

WOW! I never expected to find that Ruby 1.9.2 was 2x’s faster that 1.8.7. This definitely had me asking more questions than my mind could answer. Since then I have been writing benchmarks for all sorts of code I had written and am quickly realizing what I was taught wasn’t code optimizing at all, it was code convoluting! But thats a whole other post.

I have included below some links for Ruby Benchmark, the RubyInline gem that allows awesome C extensions within ruby as well as a link to Antonio Cangiano’s post called “The Great Ruby Shootout (July 2010)” which has a wealth of information to absorb.

Ruby Benchmark

RubyInline

The Great Ruby Shootout

Tags Ruby Benchmark RubyInline