From: Robert Klemme <shortcutter@...>
Date: 2008-03-17T22:04:52+09:00
Subject: Re: Ruby "Speedup" hints?

On 17.03.2008 13:42, Marc Heiler wrote:
> Anyone of you has a few hints on how to speed up ruby code?
> (Note - not writing it, but running it ;-) )
> 
> I only have a few hints, like 5... would love to extend it.
> 
> So without further ado:
> 
> - Using << instead of += for Strings as += creates a new object
> whereas << will simply work on the current object.

I'd replace that with the general rule to avoid object creation because 
that will cover more cases (Array#concat vs. Array#+, String#gsub! vs. 
String#gsub etc.).

> - Use Inline C for critical methods (had to include that ;> )

You could argue that this does not speed up Ruby code but replaces it 
with something else.  So it's questionable whether this item should be 
on the list.

> - Reusing variable names might be better than using a lot of
> different variables

Are you talking about a fact or a guess here?  You write "might" - which 
indicates to me that this is not a proven fact.

> -  for is faster than .each on Arrays
> 
> - .last is faster than [0]

I guess you meant Array#last is faster than Array#[-1] or Array#first is 
faster than Array#[0].

> - .zero? is faster than == 0

Interesting, I did not know that.  But the difference is really small:

robert@fussel ~
$ time ruby -e '1_000_000.times { 0.zero? }'

real    0m0.748s
user    0m0.468s
sys     0m0.108s

robert@fussel ~
$ time ruby -e '1_000_000.times { 1.zero? }'

real    0m0.748s
user    0m0.483s
sys     0m0.124s

robert@fussel ~
$ time ruby -e '1_000_000.times { 0 == 0 }'

real    0m0.869s
user    0m0.561s
sys     0m0.108s

robert@fussel ~
$ time ruby -e '1_000_000.times { 1 == 0 }'

real    0m0.857s
user    0m0.562s
sys     0m0.124s

robert@fussel ~
$

> If you know a few more hints, please add!

- freeze Strings that you are going to use as Hash keys.

Often bad design makes programs slow.  While these are valid points 
often the bigger effect can be achieved by proper designing an 
application (i.e. use a Hash for frequent lookups instead of traversing 
an Aarry).

Kind regards

	robert