Issue #13750 has been updated by watson1978 (Shizuo Fujita).


Because String#casecmp? duplicates object at `rb_str_downcase()` every time, so String#casecmp? is slower than String#casecmp?


----------------------------------------
Bug #13750: Improve String#casecmp? and Symbol#casecmp? performance with ASCII string
https://bugs.ruby-lang.org/issues/13750#change-65817

* Author: watson1978 (Shizuo Fujita)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
I think String#casecmp and String#casecmp? are similar methods.
But they have different performance on ASCII string.

Seems that String#casecmp handles ASCII string only,
however it is faster than String#casecmp?.

This patch will use the code of String#casecmp with ASCII string on String#casecmp?.
But, this patch will introduce a few penalties for UTF8 string in where detect ASCII/UTF8 string.

~~~
String#casecmp? ASCII -> 61.3 % up
String#casecmp? UTF8  ->  1.3 % down
Symbol#casecmp? ASCII -> 80.0 % up
Symbol#casecmp? UTF8  ->  4.0 % down
~~~

### Before
~~~
Calculating -------------------------------------
      String#casecmp      5.961M ( 3.8%) i/s -     29.838M in   5.017907s
String#casecmp? ASCII
                          3.530M ( 8.6%) i/s -     17.554M in   5.034848s
String#casecmp? UTF8      1.252M ( 7.4%) i/s -      6.213M in   5.012168s
      Symbol#casecmp      8.555M ( 2.4%) i/s -     42.822M in   5.009280s
Symbol#casecmp? ASCII
                          4.235M ( 9.7%) i/s -     20.824M in   5.001368s
Symbol#casecmp? UTF8      1.329M ( 0.1%) i/s -      6.704M in   5.043725s
~~~

### After
~~~
Calculating -------------------------------------
      String#casecmp      5.984M ( 6.4%) i/s -     29.829M in   5.020331s
String#casecmp? ASCII
                          5.658M ( 1.5%) i/s -     28.308M in   5.004547s
String#casecmp? UTF8      1.215M ( 4.3%) i/s -      6.132M in   5.060292s
      Symbol#casecmp      8.651M ( 0.9%) i/s -     43.313M in   5.007215s
Symbol#casecmp? ASCII
                          7.462M ( 0.5%) i/s -     37.489M in   5.023892s
Symbol#casecmp? UTF8      1.275M ( 0.2%) i/s -      6.444M in   5.052743s
~~~


### Test code
~~~ruby
require 'benchmark/ips'

Benchmark.ips do |x|
  x.report "String#casecmp" do |loop|
    loop.times { "aBcDeF".casecmp("abcdefg") }
  end
  x.report "String#casecmp? ASCII" do |loop|
    loop.times { "aBcDeF".casecmp?("abcdefg") }
  end
  x.report "String#casecmp? UTF8" do |loop|
    loop.times { "\u{e4 f6 fc}".casecmp?("\u{c4 d6 dc}") }
  end

  x.report "Symbol#casecmp" do |loop|
    loop.times { :aBcDeF.casecmp(:abcdefg) }
  end
  x.report "Symbol#casecmp? ASCII" do |loop|
    loop.times { :aBcDeF.casecmp?(:abcdefg) }
  end
  x.report "Symbol#casecmp? UTF8" do |loop|
    loop.times { :"\u{e4 f6 fc}".casecmp?(:"\u{c4 d6 dc}") }
  end
end
~~~

### Patch
https://github.com/ruby/ruby/pull/1668



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>