From: "Joe Wölfel" <joe@...>
Date: 2008-09-21T09:54:05+09:00
Subject: Re: for or each?

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On 20 sept. 08, at 20:10, _why wrote:
>
> Actually for loops are faster than `each`.  Since it doesn't
> introduce a block, there's no extra scope created.  Not much faster,
> but they are used in the computer language shootout, for instance.
> _why
>

Any thoughts on the Ruby 1.9 result?  It seems like 'each' is much  
faster than either the original for loop we started talking about, or  
the non-index based one (for loop 2).  You can run the code below if  
you like.


Ruby 1.9 output:
Rehearsal --------------------------------------------------
for loop         1.240000   0.000000   1.240000 (  1.240751)
for loop 2       1.180000   0.000000   1.180000 (  1.176560)
each             0.510000   0.010000   0.520000 (  0.512496)
----------------------------------------- total: 2.940000sec

                      user     system      total        real
for loop         1.190000   0.010000   1.200000 (  1.197695)
for loop 2       1.180000   0.000000   1.180000 (  1.177620)
each             0.510000   0.000000   0.510000 (  0.508858)

Ruby 1.86 output:
Rehearsal --------------------------------------------------
for loop         2.840000   0.040000   2.880000 (  2.880437)
for loop 2       1.660000   0.000000   1.660000 (  1.661229)
each             1.750000   0.010000   1.760000 (  1.755502)
----------------------------------------- total: 6.300000sec

                      user     system      total        real
for loop         2.300000   0.000000   2.300000 (  2.307566)
for loop 2       1.660000   0.010000   1.670000 (  1.666218)
each             1.760000   0.000000   1.760000 (  1.760356)


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 "for loop 2" do
		x = 0
		100.times do
			for i in a
				x += i
			end
		end	
	end
	
   bench.report "each" do
		x = 0
		100.times do
			a.each do |i|
				x += i
			end
		end
	end
end


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