From: "byroot (Jean Boussier) via ruby-core" <ruby-core@...>
Date: 2023-01-17T17:32:52+00:00
Subject: [ruby-core:111856] [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).


> An extra map/Hash per Shape to know which ivars it contains could work

Yeah that's more what I had in mind.

> but it would pretty bad for memory footprint with 1 hashtable per Shape.

What about one every X shapes? This way you'd have to walk at most X shapes, and then to one hash lookup. X could be something relatively high like 20 or so.

----------------------------------------
Bug #19334: Defining many instance variables and accessing them is slow in Ruby 3.2.0
https://bugs.ruby-lang.org/issues/19334#change-101270

* 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?



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