> UNICODE codepoints where the UTF-8 encoding lengths are the same for lowercase and uppercase.

This very same property got me to post this [1], which sent me down the rabbithole of learning about Unicode in earnest and building my Unicode tool. Which may have an initial release some time this millennia... maybe.

1. https://news.ycombinator.com/item?id=42014045

I like burntsushi's string-searching work because it's well documented, split modularly into libraries/applications, and runs the gamut from low- to high-level (his blog posts and comments online are extremely helpful too). I use these three tools which he maintains:

Low level: memchr [1];

Medium level: Regex (Rust crate) [2];

High level: ripgrep [3].

Other names to look out for are the previously aforementioned Wojciech Muła, as well as Daniel Lemire (of simdjson [4][5]). Not SIMD-specific, but Data-Oriented Design can be a big help in terms of thinking about SIMD and cache-friendly data layout (as well as trimming down the work that the computer needs to do, generally). I've talked that to death, so I'll just link those comments here [6].

1. https://docs.rs/memchr/latest/memchr/

2. https://docs.rs/regex/latest/regex/

3. https://github.com/burntsushi/ripgrep

4. https://www.youtube.com/watch?v=wlvKAT7SZIQ

5. https://arxiv.org/pdf/1902.08318

6. https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...

Ok, so why not use a fast memcmp on the first 4-8 chars of the pattern to identify any potential match and once found, work from there to verify if a full match exists?

This is essentially what I have have been doing for years and it is very simple. I'm sure it is not always the fastest but it's not too shabby either in the real world.