[ruby-core:114711] [Ruby master Bug#19875] Ruby 2.7 -> 3.1 Performance regression in String#count

Issue #19875 has been updated by nobu (Nobuyoshi Nakada).

Status changed from Open to Feedback

It seems compiler dependent.
My results on x86_64-darwin are:

```
$ ruby -I ./benchmark/benchmark-driver/lib/ benchmark/benchmark-driver/exe/benchmark-driver ~/tmp/string_count_benchmark_driver.yml --executables=/opt/local/bin/ruby{2.7,3.{0,1,2,3}}
Calculating -------------------------------------
                     /opt/local/bin/ruby2.7  /opt/local/bin/ruby3.0  /opt/local/bin/ruby3.1  /opt/local/bin/ruby3.2  /opt/local/bin/ruby3.3 
               count                171.134                 334.699                 668.206                 666.938                 666.382 i/s -     10.000k times in 58.433576s 29.877601s 14.965446s 14.993903s 15.006408s

Comparison:
                            count
/opt/local/bin/ruby3.1:       668.2 i/s 
/opt/local/bin/ruby3.2:       666.9 i/s - 1.00x  slower
/opt/local/bin/ruby3.3:       666.4 i/s - 1.00x  slower
/opt/local/bin/ruby3.0:       334.7 i/s - 2.00x  slower
/opt/local/bin/ruby2.7:       171.1 i/s - 3.90x  slower
```

----------------------------------------
Bug #19875: Ruby 2.7 -> 3.1 Performance regression in String#count
https://bugs.ruby-lang.org/issues/19875#change-104545

* Author: iz (Illia Zub)
* Status: Feedback
* Priority: Normal
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
`String#count` became slower since Ruby 3.1. Originally found by `@Freaky`: https://github.com/ruby/ruby/pull/4001#issuecomment-1714779781

Compared using the [`benchmark-driver` gem](https://github.com/benchmark-driver/benchmark-driver).

```
$ benchmark-driver tmp/string_count_benchmark_driver.yml --rbenv '3.1.1;3.1.4;2.7.2;3.2.2;3.0.6'                                                 
Calculating -------------------------------------
                          3.1.1       3.1.4       2.7.2       3.2.2       3.0.6
               count    465.804     463.741     865.783     462.711     857.395 i/s -     10.000k times in 21.468251s 21.563768s 11.550239s 21.611783s 11.663235s

Comparison:
                            count
               2.7.2:       865.8 i/s 
               3.0.6:       857.4 i/s - 1.01x  slower
               3.1.1:       465.8 i/s - 1.86x  slower
               3.1.4:       463.7 i/s - 1.87x  slower
               3.2.2:       462.7 i/s - 1.87x  slower
```

Benchmark:


```yml
$ cat ./tmp/string_count_benchmark_driver.yml 
loop_count: 10_000
prelude: |
  html = "\nruby\n" * 1024 * 1024
benchmark:
  count: html.count($/)
```

---

*Initially, I noticed the difference between `str.count($/)` and `str.lines.size` when working on the performance improvement: https://serpapi.com/blog/lines-count-failed-deployments/*



-- 
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/