Nicola Papale 78b5f323f8 Skip alloc when updating animation path cache (#11330) ... Not always, but skip it if the new length is smaller. For context, `path_cache` is a `Vec<Vec<Option<Entity>>>`. # Objective Previously, when setting a new length to the `path_cache`, we would: 1. Deallocate all existing `Vec<Option<Entity>>` 2. Deallocate the `path_cache` 3. Allocate a new `Vec<Vec<Option<Entity>>>`, where each item is an empty `Vec`, and would have to be allocated when pushed to. This is a lot of allocations! ## Solution Use [`Vec::resize_with`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.resize_with). With this change, what occurs is: 1. We `clear` each `Vec<Option<Entity>>`, keeping the allocation, but making the memory of each `Vec` re-usable 2. We only append new `Vec` to `path_cache` when it is too small. * Fixes #11328 ### Note on performance I didn't benchmark it, I just ran a diff on the generated assembly (ran with `--profile stress-test` and `--native`). I found this PR has 20 less instructions in `apply_animation` (out of 2504). Though on a purely abstract level, I can deduce this leads to less allocation. More information on profiling allocations in rust: https://nnethercote.github.io/perf-book/heap-allocations.html ## Future work I think a [jagged vec](https://en.wikipedia.org/wiki/Jagged_array) would be much more pertinent. Because it allocates everything in a single contiguous buffer. This would avoid dancing around allocations, and reduces the overhead of one `*mut T` and two `usize` per row, also removes indirection, improving cache efficiency. I think it would both improve code quality and performance.		2024-01-13 19:33:11 +00:00
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src	Skip alloc when updating animation path cache (#11330)	2024-01-13 19:33:11 +00:00
Cargo.toml	Standardize toml format with taplo (#10594)	2023-11-21 01:04:14 +00:00