[ruby-core:111854] [Ruby master Bug#19334] Defining many instance variables and accessing them is slow in Ruby 3.2.0

Issue #19334 has been updated by byroot (Jean Boussier).


> I suppose this could be dramatically improved by storing the iv_index inside each shape, at the expense of using a bit more memory.

Actually, nevermind, the iv_index is already in the shape. The reason it's particularly slow here is that we add a new variable every time, so we have to walk back to the shape root every time to check that the variable doesn't exist yet.

So to optimize this, a hash table would be needed. IIRC Aaron mentioned that V8 use a hash table after a certain number of edges (20?).

----------------------------------------
Bug #19334: Defining many instance variables and accessing them is slow in Ruby 3.2.0
https://bugs.ruby-lang.org/issues/19334#change-101266

* Author: mame (Yusuke Endoh)
* Status: Open
* Priority: Normal
* Assignee: tenderlovemaking (Aaron Patterson)
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
```
class C
  eval("def initialize; #{ (0..100000).map { "@x#{ _1 } = 0; " }.join } end")
  attr_reader :x50000
end
p :start
C.new.x50000
```

This script takes less than one second in Ruby 3.1.3, and does more than ten second in Ruby 3.2.0.

```
$ time ruby -v test.rb
ruby 3.1.3p185 (2022-11-24 revision 1a6b16756e) [x86_64-linux]
:start

real    0m0.210s
user    0m0.167s
sys     0m0.044s
```

```
$ time ruby -v test.rb
ruby 3.2.0 (2022-12-25 revision a528908271) [x86_64-linux]
:start

real    0m11.026s
user    0m10.950s
sys     0m0.040s
```

This problem is not critical, but is there any room for improvement?



-- 
https://bugs.ruby-lang.org/
 ______________________________________________
 ruby-core mailing list -- [e-mail]
 To unsubscribe send an email to [e-mail]
 ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/