[WIP] Replace rayon with WIP latch-target-thread branch.

[tdaede]

No description provided.

[jamrial]

Wouldn't it be safer to include a known good snapshot of this branch inside the crates folder, and use that instead of a remote private branch that may change in unpredictable ways?

Also, https://doc.rust-lang.org/edition-guide/rust-2018/cargo-and-crates-io/replacing-dependencies-with-patch.html mentions that [patch] should be used instead of [replace].

[coveralls]

Coverage remained the same at 75.614% when pulling f27967f on tdaede:rayon_replace into 9e1c711 on xiph:master.

[tdaede]

Yes, sorry I forgot to mark this WIP. I'd rather figure out why this is the case (the rayon branch is not supposed to improve performance, just reduce cpu utilization of idle threads) and then get a full release of rayon.

[lu-zero]

With this patch on top of 7344dae, Bosphorus 4k 8bit.

4x4 tiles on a 8 threads i7:

encoded 600 frames, 0.292 fps, 5481.45 Kb/s

7344dae alone:

encoded 69 frames, 0.279 fps, 6129.46 Kb/s