kentcowgill.org/blog

Going through some old code reviews, I found the following in some of my notes.

The idea was that there's a hunk of code that needs to produce a sorted and unique list of items. That description immediately brings to mind a few data types - an array and a hash - and a sort of some kind or another.

The code I encountered looked like this:

Don't get me wrong - that does do what it's supposed to do. But does it do it efficiently? Not really - that can all be replaced by the following:

Which has the following benefits:

1. Much more succint.
2. Many fewer temporary variables.
3. More perlish.
4. Quite a bit faster.

How much faster? It depends a little on the size of the data passed to it. I found that most of the time, the data coming to it was very very small, but occasionally would have much larger data sets to sort. I recall having some spare time and more curiousity then is likely good for me, so I set up some benchmarks:

First, results from running the routines
500000 times on a tiny data set:
                Rate    Original New version
Original     98232/s          --        -71%
New version 342466/s        249%          --

Next, results from running the routines
200000 times on a small data set:
                Rate    Original New version
Original     61920/s          --        -69%
New version 200000/s        223%          --

Now running them 10000 times on a
larger data set:
              Rate    Original New version
Original    4032/s          --        -49%
New version 7937/s         97%          --