slow iterators in ruby 1.9 on mac

Stefan — Tue, 17 Jun 2008 22:45:00 +0200

If you ever wondered why your Ruby programs are not faster but much slower with Ruby 1.9 you might be using each or times iterators on large collections.

10000000.times {}

In fact if you do a benchmark,

require 'benchmark'

n = 10000000

Benchmark.bm do |x|
  x.report { n.times {} }
end

you get stunning results.

$ ruby bench.rb
   user     system      total        real
   0.720000   0.000000   0.720000 (  0.721872)
$ ruby1.9 bench.rb 
   user     system      total        real
   16.670000   9.110000  25.780000 ( 25.923977)

When increasing the number of iterations by powers of ten it looks like the computational complexity of the times iterator is O(n) in Ruby 1.9. According to Antonio Cangiano this behaviour is specific to Mac OS X and does not appear on Linux.

loopkid: slow iterators in ruby 1.9 on mac

slow iterators in ruby 1.9 on mac