From: "Joe Wölfel" <joe@...>
Date: 2008-09-21T07:26:03+09:00
Subject: Re: for or each?

You can try my test if you like.  I haven't checked it carefully.   
But it does seem like 'each' is much faster under both ruby 1.86 and  
ruby 1.9.  The code is below.


require 'rubygems'
require 'benchmark'

a = (1..10000).to_a
Benchmark.bmbm 15 do |bench|

	bench.report "for loop" do
		x = 0
		100.times do
			for i in 0...(a.size)
				x += a[i]
			end
		end	
	end
	
   bench.report "each" do
		x = 0
		100.times do
			a.each do |i|
				x += i
			end
		end
	end
	
end

Joe
On 20 sept. 08, at 18:17, Phlip wrote:

> Joe Wölfel wrote:
>
>> It's interesting that array access using 'each' seems to be much   
>> faster on my machine.
>
> Does 'for' reevaluate its range after each tick? That would give  
> 'for' a single technical advantage over .each, in the very rare  
> chance you need that.
>
> Otherwise, where does the time go?
>
> A quick experiment with RubyNode just showed Ruby generates  
> different opcodes for 'each' and 'for'. (By contrast, the notorious  
> ternary operator, ? :, generates the same opcodes as an equivalent  
> 'if then else end' construction.)
>
> -- 
>   Phlip
>