Issue #19875 has been updated by nobu (Nobuyoshi Nakada). Freaky (Thomas Hurst) wrote in #note-12:
I see a difference if I configure with cflags=-msse4.2 - it's off by default. We probably want some runtime CPU feature detection if people are actually going to use it.
Who/what do you mean by "we"? It feels like a compiler's (or optimizer's) job.
There's also an AVX version of the algorithm that operates in 32-byte chunks instead of SSE's 16. I measure it as twice as fast again on my Ryzen 5700X - I might port that too if there's interest.
You may want to discuss it with compiler porting teams. ---------------------------------------- Bug #19875: Ruby 3.0 -> 3.1 Performance regression in String#count https://bugs.ruby-lang.org/issues/19875#change-104651 * Author: iz (Illia Zub) * Status: Open * 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/* ---Files-------------------------------- rb_str_len.fast (31.9 KB) rb_str_len.slow (34 KB) revert-4001.patch (1.71 KB) rb_str_count.S (11.8 KB) -- https://bugs.ruby-lang.org/