From: Todd Benson <caduceass@...>
Date: 2008-03-30T22:47:12+09:00
Subject: Re: Help on best way to gather/sort results ?

On Sat, Mar 29, 2008 at 8:45 PM, Tony De <tonydema@gmail.com> wrote:
>
> Todd Benson wrote:
>  > On Sat, Mar 29, 2008 at 1:55 AM, Tony De <tonydema@gmail.com> wrote:
>  >>
>  >>  Oooooooo!  We'll that makes perfect sense.  Thanks!  You know, sometimes
>  >>  you read your handy pickaxe or a blog somewhere, buy it slides right
>  >>  past you.  I appreciate the clarification.
>  >>
>  >>  tonyd
>  >
>  > They all work.  I use #sort_by all the time for legibility, and I
>  > don't care that much about speed for the stuff I work on.  According
>  > to the docs, sort_by doesn't scale by speed for small key sets and
>  > large populations (that might be your case).  It does, however,
>  > perform better when there occurs object creation for the comparison
>  > test.
>  >
>  > Todd
>
>  Thanks Jesus & Todd for your posts also.  I appreciate the education.
>  Forums are great for getting real world experience on language usage and
>  gotcha's.  So I do have another question on my sort.  I realize that in
>  addition to the sort on the second element in each row of my array
>  (sourceip) I would also like to then sort on the third element (email).
>  So my current sort is:
>
>
>  @results.sort! {|x, y| y[1] <=> x[1]}
>
>  So this now sorts first by element[2] and then by element[3]:
>  new_results = @results.sort_by { |x| [x[1], x[2]] }
>
>  There are so many ways to accomplish the same result.  That dosen't
>  mean, however, it's the most efficient.  Would there be a more efficient
>  way to do this?  Not that this script is costing me a great deal in
>  resources.  But it nice to code tight when possible.  Thanks again.
>
>
>
>  tonyd

On my machine...

a = [[3, 2, 1], [4, 5, 6], [1, 5, 7], [1, 2, 3]]

t = Time.now
10_000.times do
  a.sort_by {|x| [x[1], x[2]]}
end
puts Time.now - t

t = Time.now
10_000.times do
  a.sort {|x,y| [x[1], x[2]] <=> [y[1], y[2]]}
end
puts Time.now - t

10_000.times do
  a.sort! {|x,y| [x[1], x[2]] <=> [y[1], y[2]]}
end
puts Time.now - t

=> 0.25 #sort_by
=> 0.453 #sort
=> 0.859 #sort!


This may be due to the creation of addition Array objects within the block.

Just a guess.

Todd