Benchmarking of square root getting operations in different Ruby implementations.

square_root_benchmark.rb

require 'benchmark'

=begin

Math.sqrt(x) is consistently slower then x ** 0.5 in all major ruby implementations.

=end


SIZE = 1e6

ary = Array.new(SIZE) { rand(SIZE) }

Benchmark.bm do |x|
  x.report("Math.sqrt:") { ary.map { |item| Math.sqrt(item) } }
  x.report("** 0.5:   ") { ary.map { |item| item ** 0.5} }
end

=begin

Results:

ruby 1.8.7 (2012-10-12 patchlevel 371) [x86_64-linux]
      user     system      total        real
Math.sqrt:  0.500000   0.020000   0.520000 (  0.546235)
** 0.5:     0.340000   0.020000   0.360000 (  0.379318)

ruby 1.9.3p362 (2012-12-25 revision 38607) [x86_64-linux]
       user     system      total        real
Math.sqrt:  0.860000   0.020000   0.880000 (  0.925877)
** 0.5:     0.280000   0.010000   0.290000 (  0.377911)

ruby 2.0.0dev (2012-12-21 trunk 38523) [x86_64-linux]
       user     system      total        real
Math.sqrt:  0.480000   0.000000   0.480000 (  0.513030)
** 0.5:     0.230000   0.000000   0.230000 (  0.243301)

jruby 1.7.1 (1.9.3p327) 2012-12-03 30a153b on Java HotSpot(TM) 64-Bit Server VM 1.7.0_10-b18 [linux-amd64]
       user     system      total        real
Math.sqrt:  1.350000   0.030000   1.380000 (  1.472000)
** 0.5:     0.210000   0.010000   0.220000 (  0.225000)

rubinius 2.0.0rc1 (1.8.7 a06055d7 2012-11-02 JI) [x86_64-unknown-linux-gnu]
      user     system      total        real
Math.sqrt:  1.564762   0.022997   1.587759 (  1.996607)
** 0.5:     0.718890   0.005999   0.724889 (  0.810936)

=end