Question

I need to run both sort! and uniq! on an array. Which is better to run first? Or is there a way to combine these into one command?

Answer 1

I made a little benchmark test with different combinations of uniq uniq! sort and sort!
There are no significant differences:

                user     system      total        real
sort!.uniq!103.547000   0.172000 103.719000 (104.093750)
uniq!.sort!100.437000   0.093000 100.530000 (100.859375)
uniq.sort 100.516000   0.157000 100.673000 (101.031250)
sort.uniq 103.563000   0.062000 103.625000 (103.843750)

What you may not use is something like:

array = [1]
array.uniq!.sort!

uniq! will result in nil and sort! will throw an exception.

The benchmark I used:

require 'benchmark'
require 'date'

TEST_LOOPS = 10_000
ARRAY = []
1000.times{ 
  ARRAY << Date.new(1900 + rand(100), rand(11)+1, rand(27) + 1 ) 
}
Benchmark.bm(10) {|b|

  b.report('sort!.uniq!') {
   TEST_LOOPS.times { 
      a = ARRAY.dup
      a.sort!
      a.uniq!
   }            #Testloops
  }             #b.report

  b.report('uniq!.sort!') {
   TEST_LOOPS.times { 
      a = ARRAY.dup
      # uniq!.sort! not possible. uniq! may get nil
      a.uniq!
      a.sort!
   }            #Testloops
  }             #b.report

  b.report('uniq.sort') {
   TEST_LOOPS.times { 
      a = ARRAY.dup.uniq.sort
   }            #Testloops
  }             #b.report

  b.report('sort.uniq') {
   TEST_LOOPS.times { 
      a = ARRAY.dup.sort.uniq
   }            #Testloops
  }             #b.report

} #Benchmark