Issue #10227 has been updated by Masaki Matsushita.


Result of benchmark script the same as ruby-core:64954.

```
Rehearsal --------------------------------------------
include?   0.100000   0.000000   0.100000 (  0.093951)
index      0.090000   0.000000   0.090000 (  0.092334)
----------------------------------- total: 0.190000sec

               user     system      total        real
include?   0.090000   0.000000   0.090000 (  0.081303)
index      0.080000   0.000000   0.080000 (  0.081296)
```

----------------------------------------
Feature #10227: array.include? is much slower than array.index
https://bugs.ruby-lang.org/issues/10227#change-49022

* Author: A N
* Status: Closed
* Priority: Normal
* Assignee: Masaki Matsushita
* Category: core
* Target version: current: 2.2.0
----------------------------------------
I benchmarked both, and found that `include?` is about ten times slower than `index` (for the test below).

~~~
require 'benchmark'

a = (1..1_000_000).to_a
num = 100_000
reps = 100

Benchmark.bmbm do |bm|
  bm.report('include?') do
    reps.times { a.include? num }
  end
  bm.report('index') do
    reps.times { a.index num }
  end
end

               user     system      total        real
include?   0.330000   0.000000   0.330000 (  0.334328)
index      0.040000   0.000000   0.040000 (  0.039812)
~~~

As per bug #8820, `index` has been optimised to use rb_equal_opt [1], whereas `includes?` uses rb_equal [2]. (Changelog here [3].)

[1] https://github.com/ruby/ruby/blob/c6da45b74cf9d420803c6ccbf4d527b1dfe4014e/array.c#L1462
[2] https://github.com/ruby/ruby/blob/c6da45b74cf9d420803c6ccbf4d527b1dfe4014e/array.c#L3851
[3] http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?revision=42704&view=revision



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