From: aero6dof@... (Alan Chen)
Date: 2003-10-03T02:07:07+09:00
Subject: Re: Array and hash iteration questions

"Robert Klemme" <bob.news@gmx.net> wrote in message news:<blgp2a$bvnb8$1@ID-52924.news.uni-berlin.de>...
> No need to use a Hash for this...
> 
> Number = 0
> Errors = 1
> 
> cases[case][Number] += 1
> cases[case][Errors] += 1 if arr[OFFSET] =~ /Error/
> 
> I might be a bit pricky, but storing the array ref saves one hash lookup.
> It *can* affect performance if you have a large amount of cases...  (see
> below; although the timing is dominated by the iteration here, you can see
> that the array is faster)

I'm not sure if my testing method is quite consistent, but making a specific
record object looks like it could speed things up even more...

>ruby -rprofile lookups.rb
  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name
 73.74    13.08     13.08        3  4359.00  5911.67  Integer#upto
 14.47    15.64      2.57   100001     0.03     0.03  Hash#[]
 11.79    17.73      2.09   100001     0.02     0.02  Array#[]
  0.08    17.75      0.01        1    15.00    15.00  Profiler__.start_profile
  0.00    17.75      0.00        1     0.00 17735.00  #toplevel
  0.00    17.75      0.00        1     0.00     0.00  Class#inherited
  0.00    17.75      0.00        1     0.00  1329.00  Object#testObj
  0.00    17.75      0.00        2     0.00  8203.00  Object#test
  0.00    17.75      0.00        1     0.00     0.00  TestObj#initialize
  0.00    17.75      0.00        1     0.00  8203.00  Object#testArray
  0.00    17.75      0.00        9     0.00     0.00  Module#method_added
  0.00    17.75      0.00        1     0.00  8203.00  Object#testHash
  0.00    17.75      0.00        1     0.00     0.00  Module#attr_accessor
  0.00    17.75      0.00        1     0.00     0.00  Class#new
>type lookups.rb
def test(coll)
  0.upto( 100000 ) do
    coll[2]
  end
end

def testHash
  test( { 0 => 0, 1 => 1, 2 => 2 } )
end

def testArray
  test( [0, 1, 2] )
end


# a simple record class...
class TestObj
  attr_accessor :num, :err
  def initialize
    @num = 0
    @err = 0
  end
end

def testObj
  to = TestObj.new
  0.upto( 100000 ) do
    to.err
  end
end

testHash
testArray
testObj

> 10:17:02 [ruby]: ruby -rprofile lookups.rb
>   %   cumulative   self              self     total
>  time   seconds   seconds    calls  ms/call  ms/call  name
>  62.50    13.93     13.93        2  6962.50 11140.50  Integer#upto
>  26.22    19.77      5.84   100001     0.06     0.06  Hash#[]
>  11.28    22.28      2.51   100001     0.03     0.03  Array#[]
>   0.07    22.30      0.01        1    15.00    15.00
> Profiler__.start_profile
>   0.00    22.30      0.00        2     0.00 11140.50  Object#test
>   0.00    22.30      0.00        3     0.00     0.00  Module#method_added
>   0.00    22.30      0.00        1     0.00 11171.00  Object#testArray
>   0.00    22.30      0.00        1     0.00 22281.00  #toplevel
>   0.00    22.30      0.00        1     0.00 11110.00  Object#testHash