> It's good to hear that there's an idiomatic Rust way of doing this that doesn't require unsafe but is still performant. I figured there was, but to an outsider it was not obvious how.

Yeah, I mean, the reddit thread way up this comment chain talks about how Rayon should have been used, but the discoverability issue is real.

> It is also not obvious at all that this is part of the "nursery" and is not an official Rust document (the "Rust Cookbook" makes it seem more polished than maybe it is).

Yep; it's in the URL but not everyone will see that. Like most things, this is basically an accident of history; there was a push to clean this project up and make it an official resource, but before that work was finished, all the contributors had life stuff happen and had to go do something else. So it's in this weird quasi-state where there's a ton of good in there, but also some bad. We'll get to it...

Oh, someone on Reddit posted the rayon using code https://www.reddit.com/r/programming/comments/c7sgvw/writing...

Here's an article explaining how rav1e, an AV1 encoder aiming for production quality, solves this problem: https://blog.rom1v.com/2019/04/implementing-tile-encoding-in...