From: Josh Cheek <josh.cheek@...>
Date: 2010-11-01T01:39:50+09:00
Subject: Re: Is this an effective loop

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On Sun, Oct 31, 2010 at 5:15 AM, Robert Klemme
<shortcutter@googlemail.com>wrote:

>
> Regardless, the big thing we see is that the loops all perform roughly
>> equivalently overall.  Their relative differences in overhead will
>> likely be dwarfed by the looped operations in the real world.
>>
>
> Agreed.
>
>
FWIW, on mine they were not close. The while loop was much faster on every
implementation except MRI 1.8.6 and 1.8.7

I used your benchmark, except switched bmbm with just bm, for readability of
output (the results were not significantly different).
http://gist.github.com/656788

I don't know how to take that, I would have expected while loop to be
significantly slower than all of the rest.

Also, interestingly, check out Macruby! Peter Cooper wrote an article about
it recently, I think I'll go re-read it.



>     for i in 1..layers[0].count-1
>>      puts i
>>    end
>>
>> Is it equivalent in efficiency to this?
>>
>> int i = 1
>> while i < layers[0].count-1
>>   puts i
>> i+=1
>> end
>>
>
> The answer is no because the second one does one less iteration. :-)
>
>
Also, the top one calculates layers[0].count-1 only once. The bottom one
re-evaluates that expression every time. That makes the bottom one less
efficient (I am truly stunned that it won the benchmarks so thoroughly), and
could also mean they behave differently depending on what you do in the
loop.


layers = [1,2,3,4,5]

for i in 1..(puts "FOR LOOP"; layers.size-1)
end

i = 1
while i < (puts "WHILE LOOP"; layers.size-1)
  i+=1
end

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