Experiment with different hostname-to-names algorithms

➜  publicsuffix-ruby git:(thesis-hash) ✗ ruby benchmarks/bm_parts.rb
Warming up --------------------------------------
          tokenizer1    26.384k i/100ms
          tokenizer2    26.571k i/100ms
          tokenizer3    32.293k i/100ms
          tokenizer4    27.595k i/100ms
Calculating -------------------------------------
          tokenizer1    310.488k (± 6.6%) i/s -      1.557M in 5.035961s
          tokenizer2    308.801k (± 8.3%) i/s -      1.541M in 5.027643s
          tokenizer3    378.716k (± 5.3%) i/s -      1.905M in 5.045422s
          tokenizer4    305.493k (± 9.6%) i/s -      1.518M in 5.018550s

Comparison:
          tokenizer3:   378716.5 i/s
          tokenizer1:   310488.3 i/s - 1.22x  slower
          tokenizer2:   308800.6 i/s - 1.23x  slower
          tokenizer4:   305493.5 i/s - 1.24x  slower

benchmarks/bm_names.rb

@@ -0,0 +1,91 @@
+require 'benchmark/ips'
+
+STRING = "www.subdomain.example.com"
+ARRAY  = %w(
+  com
+  example.com
+  subdomain.example.com
+  www.subdomain.example.com
+)
+
+def tokenizer1(string)
+  parts = string.split(".").reverse!
+  index = 0
+  query = parts[index]
+  names = []
+
+  loop do
+    names << query
+
+    index += 1
+    break if index >= parts.size
+    query = parts[index] + "." + query
+  end
+  names
+end
+
+def tokenizer2(string)
+  parts = string.split(".")
+  index = parts.size - 1
+  query = parts[index]
+  names = []
+
+  loop do
+    names << query
+
+    index -= 1
+    break if index < 0
+    query = parts[index] + "." + query
+  end
+  names
+end
+
+def tokenizer3(string)
+  isx = string.size
+  idx = string.size - 1
+  names = []
+
+  loop do
+    isx = string.rindex(".", isx - 1) || -1
+    names << string[isx + 1, idx - isx]
+
+    break if isx <= 0
+  end
+  names
+end
+
+def tokenizer4(string)
+  isx = string.size
+  idx = string.size - 1
+  names = []
+
+  loop do
+    isx = string.rindex(".", isx - 1) || -1
+    names << string[(isx+1)..idx]
+
+    break if isx <= 0
+  end
+  names
+end
+
+(x = tokenizer1(STRING)) == ARRAY or fail("tokenizer1 failed: #{x.inspect}")
+(x = tokenizer2(STRING)) == ARRAY or fail("tokenizer2 failed: #{x.inspect}")
+(x = tokenizer3(STRING)) == ARRAY or fail("tokenizer3 failed: #{x.inspect}")
+(x = tokenizer4(STRING)) == ARRAY or fail("tokenizer4 failed: #{x.inspect}")
+
+Benchmark.ips do |x|
+  x.report("tokenizer1") do
+    tokenizer1(STRING).is_a?(Array)
+  end
+  x.report("tokenizer2") do
+    tokenizer2(STRING).is_a?(Array)
+  end
+  x.report("tokenizer3") do
+    tokenizer3(STRING).is_a?(Array)
+  end
+  x.report("tokenizer4") do
+    tokenizer4(STRING).is_a?(Array)
+  end
+
+  x.compare!
+end