[v_lisivka]

If you discard regexredux, then Rust is faster than C and C++ at average: see average bar at "How many times slower graph" [1].

regexredux program is outlier in Rust, because replacement of a regex in string is slower in regex crate, because author of regex crate chose to implement safer, but slower algorithm. To fix this, regex crate must be updated or replaced. I spent two weekends on this.

[1]: https://benchmarksgame-team.pages.debian.net/benchmarksgame/...

[igouy]

> To fix this, regex crate must be updated or replaced.

I somehow doubt pcre2 is being changed to make the tiny toy C programs run better.

> I spent two weekends on this.

So shouldn't we assume the program performance simply reflects all-those-hours you've spent working on it?

[v_lisivka]

Look at the program:

  fn find_replaced_sequence_length(sequence: String) -> usize {
    // Replace the following patterns, one at a time:
    let substs = vec![
        ("tHa[Nt]", "<4>"),
        ("aND|caN|Ha[DS]|WaS", "<3>"),
        ("a[NSt]|BY", "<2>"),
        ("<[^>]*>", "|"),
        ("\\|[^|][^|]*\\|", "-"),
    ];
  
    // Perform the replacements in the sequence:
    substs
        .iter()
        .fold(sequence, |s, (re, replacement)| {
            regex(re)
                .replace_all(&s, NoExpand(replacement)).into_owned()
        }).len()
  }

It measures performance of RE engine. I can switch from regex crate to PCRE2, and program performance will match C.

[igouy]

> I can switch from regex crate to PCRE2, and program performance will match C.

Perhaps it would; those measurements have not been made.

What does that have to do with re-writing libraries to make tiny toy programs run better?

What does that have to do with program performance being a proxy for programmer effort?

[igouy]

mandelbrot is outlier in Rust, because… :-)

[v_lisivka]

Because hardware acceleration is used in C and C++ versions. I will fix this soon.