From: Aaron Gifford <astounding@...>
Date: 2010-02-06T03:36:06+09:00
Subject: Fastest way to iterate over a range in steps

What's the fastest way to iterate over a range in variable increments?

For example, using irb (1.9.1):

irb(main):001:0>
a=0;s=Time.now;i=0;while(i<1000000000);a+=i;i+=5;end;e=Time.now;p
e-s;p a
8.715433734
99999999500000000
=> 99999999500000000
irb(main):002:0>
a=0;s=Time.now;Range.new(0,1000000000,true).step(5){|i|a+=i};e=Time.now;p
e-s;p a
18.932204045
99999999500000000
=> 99999999500000000

As you can see I'm stepping by 5 over the range 0 to 1000000000
exclusive (excluding the last item) doing a simple operation each
iteration (the operation above is totally contrived).

In this case, it appears that while outperforms Range's step method.

Wondering,
Aaron out.