Provide a benchmark between *_with? and select+regexp

[wolflee]

Please do NOT merge, only for reference purpose.

run rspec spec/bm.rb to see the results

[wolflee]

@fahchen

[fahchen]

I'm afraid that there is something wrong with your code.

2.2.3 :006 > code = 110100
 => 110100
2.2.3 :007 > gb2260 = GB2260.new
 => #<GB2260:0x007f8b3b7dcd50 @revision="2014">
2.2.3 :008 > gb2260.regex_prefectures code
 => [#<GB2260::Division:0x007f8b3b3c2120 @code="110100", @name="市辖区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c2080 @code="110101", @name="东城区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1fb8 @code="110102", @name="西城区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1f18 @code="110105", @name="朝阳区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1e78 @code="110106", @name="丰台区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1db0 @code="110107", @name="石景山区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1d38 @code="110108", @name="海淀区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1c98 @code="110109", @name="门头沟区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1bd0 @code="110111", @name="房山区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1b30 @code="110112", @name="通州区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1a90 @code="110113", @name="顺义区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c19c8 @code="110114", @name="昌平区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1950 @code="110115", @name="大兴区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c18b0 @code="110116", @name="怀柔区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c17e8 @code="110117", @name="平谷区", @revision="2014">, #<GB2260::Division:0x007f8b3b3c1748 @code="110200", @name="县", @revision="2014">, #<GB2260::Division:0x007f8b3b3c16a8 @code="110228", @name="密云县", @revision="2014">, #<GB2260::Division:0x007f8b3b3c15e0 @code="110229", @name="延庆县", @revision="2014">]
2.2.3 :009 > gb2260.prefectures code
 => [#<GB2260::Division:0x007f8b3b25b818 @code="110100", @name="市辖区", @revision="2014">, #<GB2260::Division:0x007f8b3b25b728 @code="110200", @name="县", @revision="2014">]
2.2.3 :010 >

Here is my code and benchmark https://gist.github.com/fahchen/04c126e7c2eddeda9fe6

[wolflee]

Nice catch! (and the regex)
But that's just showing that regex is more error-prone to noobs(like me) and less human readable.

Actually if we change the method like this:

  def prefectures(province_code)
    province_prefix = province_code.to_s[0,2].freeze
    Division.batch(all_code
      .select { |c| c.start_with?(province_prefix) }
      .select { |c| c.end_with?(PREFECTURE_SUFFIX) }
      .reject { |c| c.end_with?(PROVINCE_SUFFIX) },
    @revision)
  end

We can get even better performance:
Total allocated: 61239 bytes (62 objects)

The old code does a ton of allocations because it send the filter method symbols on-the-fly. The only reason it was made like this is to avoid CodeClimate duplication penalty. So if we really want the performance, we must bare with the lower CodeClimate GPA and don't "cheat" any more.

[fahchen]

+1 for the lastest code

Calculating -------------------------------------
   prefectures.start_with?   143.000  i/100ms
   prefectures.regex    62.000  i/100ms
-------------------------------------------------
   prefectures.start_with?      1.464k (± 8.7%) i/s -      7.293k
   prefectures.regex    681.787  (± 3.5%) i/s -      3.410k

Comparison:
   prefectures.start_with?:     1464.1 i/s
   prefectures.regex:      681.8 i/s - 2.15x slower

[wolflee]

Closing this as come up with a better solution.