From: Peter Vandenabeele <peter@...>
Date: 2012-01-23T23:39:25+09:00
Subject: Re: uniq with count; better way?

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On Mon, Jan 23, 2012 at 3:08 PM, Karsten Meier <
developer@handylearn-projects.de> wrote:

> Ok, I tried some benchmarks. We have now even more variables, as they
> also depend on "maxval" from the dataset.
>
> maxval = 1000
> ar = [].tap{|a| 1_000_000.times {a << rand(maxval)}}
>
> b.report("Meier:") {
>  n.times {
>    hist =  Array.new(maxval+1, 0)
>    ar.each{|x| hist[x] += 1;}
>    result = Hash.new(0)
>    0.upto(maxval){|i| result[i] = hist[i] unless hist[i] == 0}
>    result
>  }
> }
>
>
>
> On my jruby and my windows- mri 1.8.7 my algorithm was fastest for
> maxvalue of 10, 100 or 10000, for example:
>
> SIZE
> 1000000
> MAXVAL
> 10000
>                     user     system      total        real
> Ralph Shneiver:  0.533000   0.000000   0.533000 (  0.518000)
> Meier:           0.312000   0.000000   0.312000 (  0.312000)
> Keinich #1       0.814000   0.000000   0.814000 (  0.814000)
>
> (I have no 1.9.3 yet on my windows PC, so it may be different there)
>

Interesting.

I added your algorithm to the list and tested on ruby 1.9.3

$ ruby -v
ruby 1.9.3p0 (2011-10-30 revision 33570) [i686-linux]

SIZE
1000000
MAXVAL
1000
                      user     system      total        real
Ralph Shneiver:   0.370000   0.000000   0.370000 (  0.369229)
Sigurd:           0.420000   0.000000   0.420000 (  0.418634)
Meier:            0.270000   0.000000   0.270000 (  0.274136)
Keinich #1        0.320000   0.000000   0.320000 (  0.320962)
Keinich #2        0.380000   0.000000   0.380000 (  0.372422)
Magnus Holm:      0.420000   0.000000   0.420000 (  0.423316)
Abinoam #1:       0.600000   0.000000   0.600000 (  0.597028)

And I also retested in the latest jruby-head (1.7.0.dev)

$ ruby -v
jruby 1.7.0.dev (ruby-1.8.7-p357) (2012-01-23 f80ab05) (Java HotSpot(TM)
Server VM 1.6.0_26) [linux-i386-java]

SIZE
1000000
MAXVAL
1000
                     user     system      total        real
Ralph Shneiver:  0.492000   0.000000   0.492000 (  0.476000)
Sigurd:          0.473000   0.000000   0.473000 (  0.473000)
Meier:           0.287000   0.000000   0.287000 (  0.287000)
Keinich #1       0.308000   0.000000   0.308000 (  0.308000)
Keinich #2       7.374000   0.000000   7.374000 (  7.374000)
Magnus Holm:   NoMethodError: undefined method `each_with_object' for
#<Array:0x19c6163>
   __file__ at sb.rb:30
      times at org/jruby/RubyFixnum.java:261
...

So, at least for these 2 cased, your algorithm seems somewhat
faster.

As long as the array is not "sparsely" populated, this
approach certainly makes sense.

HTH,

Peter

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