From: Thomas Sondergaard <thomas@...>
Date: 2003-09-22T10:48:16+09:00
Subject: Re: Performance: Ruby vs Java

The difference is that ruby is interpreted and has a dynamic nature that
makes it difficult to optimize (or so I understand), while java is jitted
and for this single non-OO example it is probably as fast as C.

I can't resist the temptation of plugging my own project rubydotnet, which
allows you to implement such performance critical code in a .net language.

CS_SCRIPT = <<-EOF
    int n = (int) args[0];
    for (int i=0; i<n-1; ++i)
      for (int j=0; j<n-1; ++j)
        if (j*i == n)
          return false;
    return true;
  EOF

def isPrime(n)
  cs_eval(CS_SCRIPT, n)
end

puts isPrime(2)
puts isPrime(4)
puts isPrime(7)
puts isPrime(25)
puts isPrime(400003)

On my laptop (3ghz P4):
$ time ruby prime.rb
true
false
true
false
false

real    0m0.666s
user    0m0.015s
sys     0m0.000s

Neat, huh?

Cheers,

Thomas

"Lalit Pant" <lalit_pant@yahoo.com> wrote in message
news:f260fa27.0309211647.3bb8bc95@posting.google.com...
> I'm a newcomer to Ruby, and thought I would write a little
> brute-force-search program to see how Ruby compares to Java -
> performance wise. The results surprised me (I was hoping Ruby would
> fare a lot better than it did!). On my WinXP box (AthlonXP 1800+,
> 768Meg RAM), the Ruby program takes 1min 50secs to complete, while a
> similar java program takes 0.6 secs.
>
> Here are the programs:
>
> Ruby (ruby 1.8.0 (2003-08-04) [i386-mswin32]):
> def isPrime(n)
>   for i in 1..n-1 do
>     for j in 1..n-1 do
>       if i * j == n then
>         return false
>       end
>     end
>   end
>   return true
> end
>
> puts isPrime(2)
> puts isPrime(4)
> puts isPrime(7)
> puts isPrime(25)
> puts isPrime(400003)
>
> Java (HotSpot(TM) Client VM (build 1.4.2_01-b06, mixed mode)):
> public class Prime
> {
>   public static void main(String[] args)
>   {
>     Prime p = new Prime();
>     System.out.println(p.isPrime(2));
>     System.out.println(p.isPrime(4));
>     System.out.println(p.isPrime(7));
>     System.out.println(p.isPrime(25));
>     System.out.println(p.isPrime(400003));
>   }
>
>   private boolean isPrime(int n)
>   {
>     for (int i = 1; i < n; i++)
>     {
>       for (int j = 1; j < n; j++)
>       {
>         if (i*j == n)
>         {
>           return false;
>         }
>       }
>     }
>     return true;
>   }
> }
>
> Kindly note that the isPrime() method above is not meant to be the
> most efficient way of finding primes!
>
> Any ideas on why i'm seeing such a big difference in performance?