Benchmarking German non-ascii downcase

downcase_benchmark.rb

require 'benchmark'

string = "HELLO WÖRLD WHÜTS ÄP?"

n = 500_000

# Using String#tr in one fell swoop
tr_single = ->(n, str) { n.times { str.tr('A-ZÄÜÖ', 'a-zäüö') } }

# Chaining outputs of String#tr
tr_multi  = ->(n, str) { n.times { str.tr('A-Z', 'a-z').gsub('Ä','ä').gsub('Ü','ü').gsub('Ö','ö') } }

# Chaining outputs of String#gsub
gsub_mult = ->(n, str) { n.times { string.gsub('A-Z', 'a-z').gsub("Ä", "ä").gsub("Ö", "ö").gsub("Ü", "ü") } }

# Replacing umlauts with String#gsub and a dictionary
gsub_dict = ->(n, str) { n.times { string.gsub(/./, { 'A-Z' => 'a-z', "Ä" => "ä", "Ö" => "ö", "Ü" => "ü" }) }}

Benchmark.bm do |x|
  x.report("tr single") { tr_single.(n, string) }
  x.report("tr multi ")  { tr_multi.(n, string) }
  x.report("gsub mult") { gsub_mult.(n, string) }
  x.report("gsub dict") { gsub_dict.(n, string) }

  # "Native" multi-byte downcase in Ruby 2.4.0
  if RUBY_VERSION >= "2.4.0"
    x.report("2.4.0-p2 ") { n.times { string.downcase } }
  end

end
__END__
       user     system      total        real
tr single  0.620000   0.000000   0.620000 (  0.623868)
tr multi   1.810000   0.000000   1.810000 (  1.811446)
gsub mult  1.480000   0.000000   1.480000 (  1.481116)
gsub dict  4.320000   0.000000   4.320000 (  4.324333)

$ ruby -v 
ruby 2.4.0preview2 (2016-09-09 trunk 56129) [x86_64-linux]

$ ruby downcase_bench.rb 
       user     system      total        real
tr single  0.590000   0.000000   0.590000 (  0.594069)
tr multi   1.730000   0.000000   1.730000 (  1.737839)
gsub mult  1.390000   0.000000   1.390000 (  1.388327)
gsub dict  3.990000   0.000000   3.990000 (  3.991215)
2.4.0-p2   0.270000   0.000000   0.270000 (  0.268199)